This is the second Thematic Series in this journal focused on natural products. While the first series summarized recent research work on the biosynthesis and function of natural products, the present one deals with synthetic and biosynthetic aspects. Of course, the chemistry of nature and as it is used by chemists is one and the same and makes use of the same intrinsic reactivity of molecules. It is fascinating to see that a particular chemical reaction, believed to be invented by man, is in fact already used for millions of years by Mother Nature. An interesting example is the discovery of the Diels–Alder reaction in the 1920s and its later enhancement into an enantioselective reaction by the development of chiral catalysts. But a Diels–Alder reaction also occurs in the biosynthesis of lovastatin and is likely catalysed by a Diels–Alderase, a natural analogue of man-made chiral catalysts.
See also the Thematic Series:
Natural products in synthesis and biosynthesis II
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Graphical Abstract
Figure 1: The 2-methyl-4(1H)-quinolone compounds: aurachins and endochin.
Scheme 1: Synthesis of aurachin D (4) and geranyl (9), prenyl (10) and methyl (11) analogues.
Scheme 2: Strategy toward the heterocyclic core of aurachin H.
Figure 2: (A) Loss of mitochondrial membrane potential in human U-2 OS osteosarcoma cells that were treated w...
Graphical Abstract
Figure 1: Structure of the known compound theonellapeptolide Id (1).
Figure 2: Structures of sulfinyltheonellapeptolide (2) and theonellapeptolide If (3).
Figure 3: COSY and key HMBC correlations (left) and MS/MS fragmentations of 2 and its ring-opened methanolysi...
Figure 4: Antiproliferative activity of theonellapeptolides 1–3 on hepatic carcinoma cell line. The MTT assay...
Graphical Abstract
Scheme 1: Schematic nitro-Mannich reaction.
Scheme 2: Retrosynthetic analysis of piperazirum.
Scheme 3: (a) iBuMgCl, Et2O, −78 °C; (b) KOH, EtOH/H2O, 100 °C; (c) (COCl)2.
Scheme 4: (a) Li(Et3BH), THF, rt then 14, CF3CO2H, −78 °C, dr 70:30; (b) (CF3CO)2O, Py, CH2Cl2, 0 °C to rt; (...
Scheme 5: (a) Li(Et3BH), CH2Cl2, rt then 19, CF3CO2H, −78 °C, dr >95:5; (b) Zn, 6 M HCl, EtOAc/EtOH, rt, sing...
Scheme 6: (a) (COCl)2, DMF, CH2Cl2, rt; (b) 21, Py, DMAP, CH2Cl2, rt; (c) EDC, HOBt, THF/CH2Cl2, rt; (d) H2 (...
Figure 1: X-ray crystal structure of 2·HCl.
Graphical Abstract
Figure 1: Schematic diagram illustrating the phenotypic effects arising through deletion of the aziA2 gene.
Figure 2: HPLC profiles of (A) S. sahachiroi wild-type and (B) ΔaziA2 crude organic extracts.
Graphical Abstract
Figure 1: Some antibiotic natural and unnatural tetramic acids.
Scheme 1: Synthesis of simple 3-carboxamide tetramic acids. Reaction conditions: (a) triethylamine (2.0 equiv...
Scheme 2: Synthesis of N-alkyl 3-carboxamide tetramic acid. Reaction conditions: (a) 1. glycine methyl ester∙...
Scheme 3: Synthesis of C(5)-alkyl 3-carboxamide tetramic acids. Reaction conditions: (a) butyl chloroformate ...
Figure 2: Tautomerism of tetramates.
Graphical Abstract
Figure 1: Structure of symbiodinolide (1).
Scheme 1: Our previous synthesis of the C79–C96 fragment 7.
Scheme 2: Retrosynthetic analysis of the C79–C97 fragment 8.
Scheme 3: Synthesis of aldehyde 20.
Scheme 4: Synthesis of PT-sulfones 23 and 24.
Scheme 5: Synthesis of the C79–C97 fragment 27.
Graphical Abstract
Figure 1: Structure of the guaiane (−)-oxyphyllol (1).
Scheme 1: Retrosynthetic analysis for (−)-oxyphyllol (1) and structures of the guaiane sesquiterpenes (+)-ori...
Scheme 2: Attempted selective deoxygenation of diol 7. a) 1 mol % K2OsO4, NMO, acetone, water, THF, rt, 97%, ...
Scheme 3: Conversion of 4 to 1. a) 20 mol % Co(acac)2, PhSiH3, 1 atm O2, THF, 0°C, 82%, diastereomeric ratio ...
Graphical Abstract
Figure 1: a) Structural features and b) selected examples of non-natural congeners.
Scheme 1: Synthesis of isoindole 18.
Scheme 2: Staining amines with 1,4-diketone 19 (R = H).
Figure 2: Representative members of the indolocarbazole alkaloid family.
Figure 3: Staurosporine (26) bound to the adenosine-binding pocket [19] (from pdb1stc).
Figure 4: Structure of imatinib (34) and midostaurin (35).
Scheme 3: Biosynthesis of staurosporine (26).
Scheme 4: Wood’s synthesis of K-252a via the common intermediate 48.
Scheme 5: Synthesis of 26, 27, 49 and 50 diverging from the common intermediate 48.
Figure 5: Selected members of the cytochalasan alkaloid family.
Scheme 6: Biosynthesis of chaetoglobosin A (57) [56].
Scheme 7: Synthesis of cytochalasin D (70) by Thomas [63].
Scheme 8: Synthesis of L-696,474 (78).
Scheme 9: Synthesis of aldehyde 85 (R = TBDPS).
Scheme 10: Synthesis of (+)-aspergillin PZ (79) by Tanis.
Figure 6: Representative Berberis alkaloids.
Scheme 11: Proposed biosynthetic pathway to chilenine (93).
Scheme 12: Synthesis of magallanesine (97) by Danishefsky [84].
Scheme 13: Kurihara’s synthesis of magallanesine (85).
Scheme 14: Proposed biosynthesis of 113, 117 and 125.
Scheme 15: DNA lesion caused by aristolochic acid I (117) [102].
Scheme 16: Snieckus’ synthesis of piperolactam C (131).
Scheme 17: Synthesis of aristolactam BII (104).
Figure 7: Representative cularine alkaloids.
Scheme 18: Proposed biosynthesis of 136.
Scheme 19: The syntheses of 136 and 137 reported by Castedo and Suau.
Scheme 20: Synthesis of 136 by Couture.
Figure 8: Representative isoindolinone meroterpenoids.
Scheme 21: Postulated biosynthetic pathway for the formation of 156 (adopted from George) [143].
Scheme 22: Synthesis of stachyflin (156) by Katoh [144].
Figure 9: Selected examples of spirodihydrobenzofuranlactams.
Scheme 23: Synthesis of stachybotrylactam I (157).
Scheme 24: Synthesis of pestalachloride A (193) by Schmalz.
Scheme 25: Proposed mechanism for the BF3-catalyzed metal-free carbonyl–olefin metathesis [149].
Scheme 26: Preparation of the isoindoline core of muironolide A (204).
Scheme 27: Proposed biosynthesis of 208.
Scheme 28: Model for the biosynthesis of 215 and 217.
Scheme 29: Synthesis of lactonamycin (215) and lactonamycin Z (217).
Figure 10: Hetisine alkaloids 225–228.
Scheme 30: Biosynthetic proposal for the formation of the hetisine core [167].
Scheme 31: Synthesis of nominine (225).
Graphical Abstract
Figure 1: Several natural occurring anthracycline antibiotics.
Scheme 1: Total synthesis of daunomycinone 6 according to Hansen.
Scheme 2: Synthesis of simplified anthracycline derivatives.
Scheme 3: Retrosynthetic analysis of anthracycline aglycone mimics. Si: any silyl group.
Scheme 4: Synthetic route for the synthesis of various dialkynes 16. aSi: TMS, SiMe2Bn (2.0 equiv); Si: SiMe2...
Scheme 5: Silyl ether synthesis and domino carbopalladation reaction. R,R (Glc): isopropylidene. R,R (Gal): b...
Scheme 6: Derivatisation of anthracycline derivatives. aR,R (Glc): isopropylidene. R,R (Gal): benzylidene. Re...
Graphical Abstract
Figure 1: Natural products having a 1,2,4-oxadiazole core.
Figure 2: Examples of 1,2,4-oxadiazole antitumorals.
Scheme 1: Common synthetic strategies toward 1,2,4-oxadiazoles; (a) amidoxime route; (b) 1,3 dipolar cycloadd...
Scheme 2: One-pot synthesis of 4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)aniline (1) by using the amidoxime route....
Figure 3: Molecular structure of 4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)aniline (1). Atoms are drawn as 50% the...
Figure 4: Packing diagram of compound 1. Hydrogen bonds are indicated as dashed lines.
Scheme 3: One-pot synthesis of 4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)aniline (1) by using the 1,3-dipolar cycl...
Figure 5: Molecular structure of 3-tert-butyl-5-(4-nitrophenyl)-1,2,4-oxadiazole (2). Atoms are drawn as 50% ...
Figure 6: Packing diagram of compound (2) showing C–H···O interactions.
Scheme 4: Synthesis of 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)pyrrolidine-2,5-dione (4).
Figure 7: Molecular structure of 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)pyrrolidine-2,5-dione (4). At...
Figure 8: Molecular structure of 4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4 oxobutanoate (5). Ato...
Figure 9: Packing diagram of compound (5). Dashed lines indicate hydrogen bonds.
Scheme 5: Synthesis of 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)-1H-pyrrole-2,5-dione (7).
Figure 10: Molecular structure of (Z)-4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4-oxobut-2-enoic ac...
Figure 11: Packing diagram of compound 6. Dashed lines indicate hydrogen bonds.
Figure 12: In vitro antitumor activity of compounds 1, 3–7 toward 11 human tumor cell lines.
Figure 13: Individual IC50 values [µM] of compounds 1, 3–7 in a panel of 11 human tumor cell lines.
Graphical Abstract
Figure 1: Selected biocatalytic allylic and benzylic oxidations with the lyophilisate of Pleurotus sapidus (P...
Scheme 1: Biocatalytic allylic oxidation of theaspirane (1) with lyophilisates of PSA. Only one enantiomer of...
Figure 2: Selected bioactive terpenoids based on spiroether backbones [38,39].
Scheme 2: Intramolecular silyl modified Sakurai reaction to spiroethers 7–9 and 11–13.
Scheme 3: Biocatalytic allylic oxidation of spiroethers 7, 8, 11 and 12 with the lyophilisate of PSA. Convers...
Figure 3: Bond-dissociation enthalpies for three allylic C–H bonds in 11. Double stabilization of the radical...
Scheme 4: Improved 3-step synthesis of vitispirane (23) from theaspirane (1). Only one enantiomer of racemic ...
Scheme 5: Oxidation of vitispirane (23) with PSA gave enone 24 and two diastereomeric allyl alcohols 26a and ...
Graphical Abstract
Figure 1: Structures of cyclopamine and exo-cyclopamine.
Scheme 1: Synthesis of 25-epi-exo-cyclopamine 5, bis-exo-cyclopamine 6, and derivatives 8 and 9. Reaction con...
Scheme 2: Synthesis of 20-demethyl-bis-exo-cyclopamine 19 and F-nor-20,25-bis-demethyl-exo-cyclopamine 23. Re...
Figure 2: IC50 values of Shh inhibition by compounds 5, 6 and 23 in a Gli1-reporter gene assay. Data were obt...
Graphical Abstract
Figure 1: Structures of some pumiliotoxins and an advanced intermediate.
Scheme 1: Synthesis of 5 from 6 via oxidation–addition sequence.
Scheme 2: Plausible stereochemical course of the preferential axial addition of methylmagnesium iodide to bic...
Scheme 3: Holmes’ exclusive trans-diastereoselective methylation of N-Cbz-protected piperidin-3-one 8.
Scheme 4: Our plan for the trans-diastereoselective methylation of keto-lactam 10.
Scheme 5: Retrosynthetic analysis of (8S,8aS)-8-hydroxy-8-methylindolizidin-5-one (5).
Scheme 6: Synthesis of compound 18.
Scheme 7: Synthesis of hydroxylactam 18.
Scheme 8: Synthesis of tertiary alcohol 22.
Scheme 9: Synthesis of (8S,8aS)-5 and its silyl ether 23.
Graphical Abstract
Figure 1: (S)-1,3-dihydroxy-3,7-dimethyl-6-octen-2-one (1).
Scheme 1: Selective oxidation of glycerol [15] and methyl α-D-glucopyranoside.
Scheme 2: Approach of synthesis of (S)-1.
Scheme 3: Synthesis of (S)-1 from geraniol. Reagents and conditions: a) D-(−)-diisopropyl tartrate, Ti(OiPr)4...
Scheme 4: Synthesis starting from nerol. Reagents and conditions: a) L-(+)-diisopropyl tartrate, Ti(OiPr)4, t...
Graphical Abstract
Scheme 1: Synthesis of D-tagatose from D-galactose using L-arabinose isomerase.
Scheme 2: Synthesis of D-psicose from D-fructose using D-tagatose 3-epimerase/D-psicose 3-epimerase.
Figure 1: The active site in D-psicose 3-epimerase (DPEase) in the presence of D-fructose, showing the metal ...
Scheme 3: Enzymatic synthesis of D-psicose using aldolase FucA.
Scheme 4: Proposed pathway of the D-sorbose synthesis from galactitol or L-glucitol.
Scheme 5: Simultaneous enzymatic synthesis of D-sorbose and D-psicose.
Scheme 6: Biosynthesis of L-tagatose.
Scheme 7: Preparative-scale synthesis of L-tagatose and L-fructose using aldolase.
Scheme 8: Biosynthesis of L-fructose.
Scheme 9: Preparative-scale synthesis of L-fructose using aldolase RhaD.
Scheme 10: Chemoenzymatically synthesis of 1-deoxy-L-fructose [8].
Scheme 11: Potential enzymes (isomerases) for the bioconversion of D-psicose to D-allose.
Scheme 12: Three-step bioconversion of D-glucose to D-allose.
Scheme 13: Biosynthesis of L-glucose.
Scheme 14: Enzymatic synthesis of L-talose and D-gulose.
Scheme 15: Enzymatic synthesis of L-galactose.
Scheme 16: Enzymatic synthesis of L-fucose.
Scheme 17: Synthesis of allitol from D-fructose using a multi-enzyme system.
Scheme 18: Biosynthesis of D-talitol via C-2 reduction of rare sugars.
Scheme 19: Biosynthesis of L-sorbitol via C-2 reduction of rare sugars.
Graphical Abstract
Figure 1: Structure of integramycin (1) and its producing organism, Actinoplanes sp. (Photo: J. Wink, HZI, Mi...
Figure 2: Retrosynthetic analysis of integramycin.
Scheme 1: Synthesis of the aromatic subunit.
Scheme 2: Sharpless epoxidation/Myers alkylation approach to the C16–C22 carboxylic acid fragment.
Scheme 3: Coupling of the fragments and spiroketalization.
Graphical Abstract
Scheme 1: RCM/base-induced ring-opening sequence.
Figure 1: Structures and numbering scheme for stagonolide E and curvulide A.
Scheme 2: Synthetic plan for stagonolide E.
Scheme 3: Synthesis of RCM/ring opening precursor 14.
Scheme 4: Synthesis of a substrate 19 for “late stage” resolution.
Scheme 5: Synthesis of substrate 21 for “early stage” resolution.
Scheme 6: Synthesis of macrolactonization precursor 29.
Scheme 7: Synthesis of (2Z,4E)-9-hydroxy-2,4-dienoic acid (33) and its macrolactonization.
Scheme 8: Synthesis of published structure of fusanolide A (36).
Scheme 9: Completion of stagonolide E synthesis.
Scheme 10: Transition-state models for the Sharpless epoxidation of stagonolide E with L-(+)-DET (left) and D-...
Scheme 11: Synthesis of 39b (curvulide A) from stagonolide E.
Figure 2: MM2 energy-minimized structures of 39a and 39b.
Graphical Abstract
Figure 1: Antimycins: Antimycins A1, A2, A3, and A4 and non-natural antimycins referenced in the text. Antimy...
Figure 2: Schematic representation of ant biosynthetic gene clusters. L-form ant gene clusters are encoded by...
Figure 3: Proposed biosynthetic pathway for antimycins. The antimycin biosynthetic pathway is described in de...
Figure 4: σAntA comprises a new subfamily of ECF RNA polymerase σ factors. σAntA amino acid sequences were al...
Graphical Abstract
Scheme 1: Structure of jaspine B 1 and its stereoisomers 2–4.
Scheme 2: Retrosynthetic analysis of jaspine B leading to pentadecanal and an alkoxyallene.
Scheme 3: Synthesis of racemic dihydrofuran 8.
Scheme 4: Synthesis of racemic jaspine B rac-1 and its diastereomer rac-2.
Scheme 5: Synthesis of dihydrofurans 14 and 15.
Scheme 6: Synthesis of jaspine B (1) and its (2S,3R,4R)-diastereomer 2.
Scheme 7: Protection and separation of the diastereomers.
Scheme 8: Reduction of the separated diastereomers leading to jaspine B (1) and its diastereomer 2.
Scheme 9: Route to ent-jaspine B (3) and the (2R,3S,4S)-diastereomer 4.
Graphical Abstract
Figure 1: Structures of epothilone A (1), soraphen A1α (2), pyrrolnitrin (3), fenpiclonil (4), myxothiazol A (...
Figure 2: HMBC interactions used for the structure elucidation of myxocoumarin A (7).
Figure 3: Chemical structure of myxocoumarin B (9).
Scheme 1: Postulated biosynthetic pathway to myxocoumarins A (7) and B (9).
Graphical Abstract
Figure 1: Structures of limonene, carvone and thalidomide.
Figure 2: Structure of Garner’s aldehyde.
Scheme 1: (a) i) Boc2O, 1.0 N NaOH (pH >10), dioxane, +5 °C → rt; ii) MeI, K2CO3, DMF, 0 °C → rt (86% over tw...
Scheme 2: (a) AcCl, MeOH, 0 °C → reflux (99%); (b) i) (Boc)2O, Et3N, THF, 0 °C → rt → 50 °C (89%); ii) Me2C(O...
Scheme 3: (a) LiAlH4, THF, rt (93–96%); (b) (COCl)2, DMSO, iPr2NEt, CH2Cl2, −78 °C → −55 °C (99%).
Scheme 4: The Koskinen procedure for the preparation of Garner’s aldehyde. (a) i) AcCl, MeOH, 0 °C → 50 °C (9...
Scheme 5: Burke’s synthesis of Garner’s aldehyde. BDP - bis(diazaphospholane).
Figure 3: Structures of some iminosugars (7, 9), peptide antibiotics (8) and sphingosine (10) and pachastriss...
Scheme 6: Use of Garner’s aldehyde 1 in multistep synthesis.
Scheme 7: Explanation of the anti- and syn-selectivity in the nucleophilic addition reaction.
Scheme 8: Herold’s method: (a) Lithium 1-pentadecyne, HMPT, THF, −78 °C (71%); (b) Lithium 1-pentadecyne, ZnBr...
Scheme 9: (a) Ethyl lithiumpropiolate, HMPT, THF, −78 °C; (b) (S)- or (R)-MTPA, DCC, DMAP, THF, rt (18, 81%) ...
Scheme 10: Coleman’s selectivity studies and their transition state model for the co-ordinated delivery of the...
Scheme 11: (a) PhMgBr, THF, −78 °C → 0 °C [62] or (a) PhMgBr, Et2O, 0 °C [63].
Scheme 12: (a) cat. RhCl3·3H2O, cat. 26, NaOMe, Ph-B(OH)2, aq DME, 80 °C (24, 71%); (b) cat. RhCl3·3H2O, cat. ...
Scheme 13: Lithiated dithiane (3 equiv), CuI (0.3 equiv), BF3·Et2O (6 equiv), THF, −50 °C, 12 h (70%).
Scheme 14: Addition reaction reported by Lam et al. (a) 1-Hexyne, n-BuLi, THF, −15 °C or −40 °C.
Scheme 15: (a) n-BuLi, HMPT, toluene, −78 °C → rt (85%); (b) n-BuLi, ZnCl2, toluene/Et2O, −78 °C → rt (65%).
Scheme 16: (a) n-BuLi, 34, THF, −40 °C [69]; (b) n-BuLi, 35, THF, −78 °C → rt (80%) [70]; (c) n-BuLi, 35, HMPT, THF, −...
Scheme 17: (a) cat. Rh(acac)(CO)2, 42, THF, 40 °C (74%).
Scheme 18: (a) 1-PropynylMgBr, CuI, THF, Me2S, −78 °C (95%); (b) Ethynyltrimethylsilane, EtMgBr, CuI, THF, Me2...
Scheme 19: (a) cat. 50, toluene, 0 °C (52%); (b) cat. 51, toluene, 0 °C (51%); (c) cat. 52, toluene, 0 °C (50%...
Scheme 20: (a) (iPr)3SiH, cat. Ni(COD)2, dimesityleneimidazolium·HCl, t-BuOK, THF, rt.
Scheme 21: (a) Cp2Zr(H)Cl, cat. AgAsF6, CH2Cl2, rt; (b) Cp2Zr(H)Cl, 1-pentadecyne, cat. ZnBr2 in THF for anti-...
Scheme 22: (a) i) 31, n-BuLi, THF, −78 °C; ii) (S)-1, THF, −78 °C; (b) Red-Al, THF, 0 °C.
Scheme 23: (a) 61, n-BuLi, DMPU, toluene, −78 °C, then (S)-1, toluene, −95 °C (57%); (b) 61, n-BuLi, ZnCl2, to...
Scheme 24: Olefin A as an intermediate in natural product synthesis.
Scheme 25: (a) Ph3(Me)PBr, KH, benzene (66%, rac-64) or (b) AlMe3, Zn, CH2I2, THF (76%) [101]; (c) Ph3(Me)PBr, n-Bu...
Scheme 26: (a) Benzene, rt (82%) [108]; (b) K2CO3, MeOH (85%) [89]; (c) iPrOH, [Ir(COD)Cl]2, PPh3, THF, rt (81%) [114].
Scheme 27: Mechanism of the Still–Gennari modification of the HWE reaction leading to both olefin isomers.
Graphical Abstract
Figure 1: Total ion chromatogram of a CLSA headspace extract from Geniculosporium.
Figure 2: Mass spectra of A) the chlorinated volatile X and B) the chlorinated volatile Y.
Figure 3: Constitutional isomers of chlorodimethoxybenzene as candidate structures for X.
Scheme 1: Synthesis of chlorodimethoxybenzenes as reference compounds for X.
Figure 4: Constitutional isomers of dichlorodimethoxybenzene as candidate structures for Y.
Scheme 2: Synthesis of chlorodimethoxybenzenes as reference compounds for Y.
Figure 5: Known natural products that are structurally related to 4b and 10b from Geniculosporium.
Figure 6: Total ion chromatograms of headspace extracts from S. chartreusis. A) Growth on 84 GYM showing prod...
Figure 7: Calicheamicin, a known iodinated compound from the actinomycete Micromonspora echinospora.
Graphical Abstract
Figure 1: Terpenoids from Streptomyces griseus.
Figure 2: Total ion chromatograms of CLSA headspace extracts from S. griseus obtained after (A) incubation on...
Figure 3: Mass spectra of 1-epi-cubenol. (A) Mass spectrum of natural 3 obtained after growth on 65.GYM; (B) ...
Figure 4: Ion chromatograms of fully deuterated 3 for (A) the molecular ion (m/z = 248, 247, and 246), and (B...
Graphical Abstract
Figure 1: Structure of SF002-96-1.
Figure 2: COSY (bold) and HMBC (arrow) correlations of SF002-96-1.
Figure 3: NOESY correlations of SF002-96-1.
Figure 4: Effect of SF002-96-1 on survivin promoter activity, survivin mRNA levels and expression. (A) Colo 3...
Figure 5: Effect of SF002-96-1 on Sat3 and NF-κB binding to the survivin promoter in Colo 320 cells analyzed ...
Figure 6: SF002-96-1 induces apoptosis of Colo 320 cells. (A) Colo 320 cells were treated without (control) o...
Figure 7: Single-quadrupole mass spectrumof SF002-96-1 obtained using an atmospheric pressure chemical ioniza...
Graphical Abstract
Figure 1: Binding affinities of salvinorin A (1) and furan derivatives for κ-OR [5].
Figure 2: Crystal structure of κ-OR in complex with JDTic compared to naltrindole’s binding pose in δ-OR. A: ...
Figure 3: Previously reported N-furanylalkyl opioid antagonists [19,20].
Scheme 1: Syntheses of heteromethylated derivatives of 1. b.r.s.m. = based on recovered starting material.
Scheme 2: Synthesis of (2-hydroxyethoxy)methyl ether 6.
Figure 4: Crystal structure of 2 with 50% probability thermal displacement ellipsoids (cross-eyed stereoview)...
Figure 5: Key 1H–13C HMBC correlations.
Figure 6: Known low-affinity derivatives of 1 screened in addition to 2–5 for negative allosteric modulation ...
Graphical Abstract
Figure 1: (−)-(5R,6Z)-Dendrolasin-5-acetate (1), its 6E derivative and naturally occuring dentrolasin (3).
Figure 2: Selected HMBC, COSY, and nOe correlations of 1.
Scheme 1: Synthetic route to sesquiterpene 1.
Scheme 2: Mechanism of Wittig rearrangement [21].
Figure 3: (a) NP HPLC trace showing separation of racemic 5-hydroxydendrolasin (7a/b) using hexanes/EtOAc (90...
Figure 4: Analytical enantioselective HPLC trace showing separation of individual enantiomers of (6Z)-5-hydro...
Figure 5: The 1H NMR (CDCl3, 500 MHz) spectroscopic comparison of (6Z)-dendrolasin-5-acetate (1): (a) sample ...
Figure 6: RP HPLC trace showing separation of the MPA esters (R,R)-11 and (R,S)-11 (MeCN/H2O, 63:35 over 50 m...
Figure 7: Enantioselective HPLC profiles (5% isopropanol in n-hexane) of 1: (a) synthetic (±) mixture; (b) sy...
Graphical Abstract
Scheme 1: Proposed steps for DNA demethylation (for details see text).
Figure 1: Structures of the synthesized compounds.
Scheme 2: Synthesis of the 2'-deoxycytidine analogues.
Scheme 3: Reactions of TCBoc-protected aldehydes 4 and 5 with organometallic reagents.
Scheme 4: Proposed mechanism for the formation of 3,6-dihydrodeoxycytidine derivatives 8a–d (M = Li, Mg).
Graphical Abstract
Figure 1: Bisamides as building blocks for flavaglins.
Figure 2: (+)-Grandiamide D, gigantamide A and dasyclamide.
Scheme 1: Retrosynthetic analysis: A unified synthetic approach for the synthesis of grandiamide D, dasyclami...
Scheme 2: Preparation of N-(4-aminobutyl)cinnamamide.
Scheme 3: Synthesis of (±)-grandiamide D.
Scheme 4: Asymmetric synthesis of natural (+)-grandiamide D.
Scheme 5: Various approaches for the synthesis of (E)-N-(4-cinnamamidobutyl)-4-((4-methoxybenzyl)oxy)-2-methy...
Scheme 6: Synthesis of dasyclamide.
Graphical Abstract
Figure 1: Schematic procedure of the constructed assay system; Tc (tetracycline), TetR (tetracycline represso...
Figure 2: Isolated compounds from Solanum nigrum.
Figure 3: GLI1 transcriptional activity and cytotoxicity. Reporter activity (solid columns) and cell viabilit...
Figure 4: Inhibition of protein expression by compound 1. (A) Western blot analysis of PTCH, BCL-2 protein le...
Figure 5: Inhibitory activity of GLI1–DNA-complex formation by electron mobility shift assay (EMSA). GST–GLI1...
Graphical Abstract
Scheme 1: Vogel’s first approach towards the divinylcyclopropane rearrangement [4] and characterization of cis-d...
Scheme 2: Transition states for the Cope rearrangement and the related DVCPR. Ts = transition state.
Scheme 3: Two possible mechanisms of trans-cis isomerizations of divinylcyclopropanes.
Scheme 4: Proposed biosynthesic pathway to ectocarpene (21), an inactive degradation product of a sexual pher...
Scheme 5: Proposed biosynthesis of occidenol (25) and related natural compounds.
Scheme 6: Gaich’s bioinspired system using the DVCPR to mimick the dimethylallyltryptophan synthase. DMAPP = ...
Scheme 7: Iguchi’s total synthesis of clavubicyclone, part 1.
Scheme 8: Iguchi’s total synthesis of clavubicyclone, part 2.
Scheme 9: Wender’s syntheses of the two pseudoguainanes confertin (50) and damsinic acid (51) and Pier’s appr...
Scheme 10: Overman’s total synthesis of scopadulcic acid B.
Scheme 11: Davies’ total syntheses of tremulenolide A and tremulenediol A.
Scheme 12: Davies formal [4 + 3] cycloaddition approach towards the formal synthesis of frondosin B.
Scheme 13: Davies and Sarpongs formal [4 + 3]-cycloaddition approach towards barekoxide (106) and barekol (107...
Scheme 14: Davies formal [4 + 3]-cycloaddition approach to 5-epi-vibsanin E (115) containing an intermediate c...
Scheme 15: Echavarren’s total synthesis of schisanwilsonene A (126) featuring an impressive gold-catalzed casc...
Scheme 16: Davies early example of a formal [4 + 3]-cycloaddition in alkaloids synthesis.
Scheme 17: Fukuyama’s total synthesis of gelsemine, part 1.
Scheme 18: Fukuyama’s total synthesis of gelsemine, featuring a divinylcyclopropane rearrangement, part 2.
Scheme 19: Kende’s total synthesis of isostemofoline, using a formal [4 + 3]-cycloaddition, including an inter...
Scheme 20: Danishefsky’s total synthesis of gelsemine, part 1.
Scheme 21: Danishefsky’s total synthesis of gelsemine, part 2.
Scheme 22: Fukuyama’s total synthesis of gelsemoxonine.
Scheme 23: Wender’s synthetic access to the core skeleton of tiglianes, daphnanes and ingenanes.
Scheme 24: Davies’ approach towards the core skeleton of CP-263,114 (212).
Scheme 25: Wood’s approach towards actinophyllic acid.
Scheme 26: Takeda’s approach towards the skeleton of the cyanthins, utilitizing the divinylcyclopropane rearra...
Scheme 27: Donaldson’s organoiron route towards the guianolide skeleton.
Scheme 28: Stoltz’s tandem Wolff/DVCPR rearrangement.
Scheme 29: Stephenson’s tandem photocatalysis/arylvinylcyclopropane rearrangement.
Scheme 30: Padwa’s rhodium cascade involving a DVCPR.
Scheme 31: Matsubara’s version of a DVCPR.
Scheme 32: Toste’s tandem gold-catalyzed Claisen-rearrangement/DVCPR.
Scheme 33: Ruthenium- and gold-catalyzed versions of tandem reactions involving a DVCPR.
Scheme 34: Tungsten, platinum and gold catalysed cycloisomerizations leading to a DVCPR.
Scheme 35: Reisman’s total synthesis of salvileucalin B, featuring an (undesired) vinylcyclopropyl carbaldehyd...
Scheme 36: Studies on the divinylepoxide rearrangement.
Scheme 37: Studies on the vinylcyclopropanecarbonyl rearrangement.
Scheme 38: Nitrogen-substituted variants of the divinylcyclopropane rearrangement.
Graphical Abstract
Figure 1: Structures of the 4,4,8-trimethyl-17-furanylsteroid core structure I and the representative B-seco ...
Scheme 1: Retrosynthetic analysis of the B-seco limonoid framework employing a [3,3]-sigmatropic rearrangemen...
Scheme 2: Retrosynthetic analysis of the B-seco limonoid scaffold employing a Claisen rearrangement as key st...
Scheme 3: Synthesis of alcohols 19, 20 and 22. Reagents and conditions: a) CSA, 2,3-butanedione, trimethyl or...
Scheme 4: Retrosynthetic analysis of the B-seco limonoid scaffold employing an Ireland–Claisen rearrangement ...
Scheme 5: Synthesis and Ireland–Claisen rearrangement of the allyl esters 27, 28, 29 and 30. Reagents and con...
Figure 2: Conformation of rearrangement precursor 30 and possible transition state involved in the Ireland–Cl...
Scheme 6: Synthesis of model C rings 40, 41 and 42. Reagents and conditions: a) TBDPSCl, DMAP, NEt3, CH2Cl2, ...
Scheme 7: β-Substituted allyl esters tested in the Ireland–Claisen and the Carroll rearrangement.
Scheme 8: Synthesis and Ireland–Claisen rearrangement of bicyclic allyl ester precursor 66. Reagents and cond...
Figure 3: Conformations of rearrangement precursors 66 and 77 and possible transition states involved in the ...
Scheme 9: Synthesis and Ireland–Claisen rearrangement of allyl ester 70. Reagents and conditions: a) DIPEA, M...
Scheme 10: Synthesis and Ireland–Claisen rearrangement of allyl ester 72. Reagents and conditions: a) TIPSOTf,...
Scheme 11: Synthesis of the C14-epi and C14/C9-epi B-seco limonoid scaffolds 78 and 79. Reagents and condition...
Scheme 12: Synthesis of fully functionalized A ring 87. Reagents and conditions: a) HO(CH2)2OH, THF, Pd/C, H2,...
Scheme 13: and Attempted Ireland–Claisen rearrangement of allyl ester 88. R1 = MOM, R2 = CO2H.
Scheme 14: Synthesis and attempted Ireland–Claisen rearrangement of allyl ester 93. Reagents and conditions: a...
Scheme 15: Allyl esters tested in the Ireland–Claisen rearrangement.
Graphical Abstract
Figure 1: HMBC, COSY and NOESY correlations of compound 1.
Figure 2: HMBC, COSY and NOESY correlations of compound 2.
Figure 3: HMBC, COSY and NOESY correlations of compound 3.
Figure 4: HMBC, COSY and NOESY correlations of compound 4.
Figure 5: Structures of the isolated compounds.
Figure 6: Crystal structures (ORTEP plot) of arohynapene A (5, left) and tanzawaic acid E (8, right). Thermal...
Graphical Abstract
Figure 1: Structure of decandrinin (1).
Figure 2: Selected 1H–1H COSY and HMBC correlations for decandrinin (1).
Figure 3: Diagnostic NOE interactions for decandrinin (1, B97D/TZVP-optimized structure): arbitrarily the 5R,9...
Figure 4: Determination of the absolute configuration of decandrinin (1) by comparing the calculated CD spect...
Scheme 1: Proposed biosynthetic pathway for decandrinin (1).
Graphical Abstract
Figure 1: Structures of the strongly cytotoxic marine natural products malevamide D (1), isodolastatin H (2),...
Scheme 1: Total synthesis of malevamide D (1). a) DMSO (16 equiv), NEt3 (5 equiv), pyridine·SO3 (5 equiv), 0 ...
Scheme 2: Formation of oxazolylphosphate 18 on attempted DEPC-mediated coupling of dipeptide 15.
Scheme 3: Synthesis of tosyloximes (Z)-22 and (E)-22, X-ray structure of (E)-22. a) NH2OH·HCl (1.5 equiv), py...
Scheme 4: Synthesis of photo malevamide D 30. a) NH3(l), t-BuOMe, −40 °C, 2 h, rt, 16 h, quant. b) I2 (1.2 eq...
Figure 2: DSC curve of diazirine 25, heating rate 5 °C/min.
Graphical Abstract
Scheme 1: The proposed pathway for monensin biosynthesis in Streptomyces cinnamonensis. The polyketide syntha...
Figure 1: LC–MS-analysis of purified monensin-related metabolites. Monensin B derivatives (peaks marked with ...
Figure 2: (a) Crystal structure of sodium demethylmonensin A (4) (ellipsoid probability = 50%); (b) overlay o...
Graphical Abstract
Figure 1: Natural products and other bioactive piperidine derivatives of type B.
Figure 2: Retrosynthetic analysis of piperidines B (X = OH or leaving group, PG = protecting group).
Scheme 1: Synthesis of the protected amino acids 2. (a) KOH for 1b. b) PG–X = Cbz–Cl (1a–c), Boc2O (1d).
Scheme 2: Synthesis of hydroxy ketones 7 (R = Me (a), Bn (b), Ph (c) and EtSMe (d); PG = Cbz (a–c), Boc (d)).
Scheme 3: Synthesis of amides 5e and 5f and ketone 7e.
Scheme 4: Synthesis of amino alcohols syn-9a–d and oxazolidinone 10a. (for 7a–c conditions A: H2 (1 atm), Pd/...
Scheme 5: Competition between the Michaelis–Arbuzow process and the desired cyclodehydration of amino alcohol...
Scheme 6: Initial synthesis of the trans-piperidinol 11a in diminished enantiopurity. aThe amino alcohol 9a o...
Scheme 7: Synthesis of trans-piperidinol 11a in excellent ee.
Scheme 8: Synthesis of L-733,060·HCl.
Graphical Abstract
Scheme 1: Short representation of ansamitocin biosynthesis.
Scheme 2: Structures of bromo-ansamitocin derivative 6, folate-ansamitocin P-3 conjugate 7 and thiol 8.
Scheme 3: Strategies for introducing linker-based thiol groups to the aromatic moiety of ansamitocin P-3 for ...
Figure 1: m-Aminobenzoic acid derivatives 9–20 tested as mutasynthons.
Scheme 4: Mutasynthetic transformation of aminobenzoic acid 11 with AHBA(−)-mutant of A. pretiosum; putative ...
Scheme 5: Mutasynthetic transformation of aminobenzoic acid 9 with AHBA(−)-mutant of A. pretiosum to bromo-an...
Scheme 6: Mutasynthetic transformation of aminobenzoic acids 12 and 13 with AHBA(−)-mutant of A. pretiosum.
Scheme 7: Mutasynthetic transformation of vinyl(amino)benzoic acid 15 with AHBA(−)-mutant of A. pretiosum.
Scheme 8: Preparation of thiofunctionalized ansamitocin derivatives 27 by Huisgen-type copper-mediated cycloa...
Graphical Abstract
Figure 1: Structures of the new compounds siphonodictyals E1–E4 (1–4) and cyclosiphonodictyol A (5) isolated ...
Figure 2: Structures of the related known compounds siphonodictyal B1 (6), siphonodictyal B2 (7), siphonodict...
Figure 3: Selected 1H,13C-HMBC correlations (H → C) and 1H,1H-COSY correlation (bold line) observed for sipho...
Figure 4: Selected 1H,13C-HMBC correlations (H → C) observed for siphonodictyal E2 (2).
Figure 5: Possible constitutions for the aromatic moieties of siphonodictyals E2 (2) and E3 (3) (sum over all...
Figure 6: Selected 1H,13C-HMBC correlations (H → C) observed for siphonodictyal E4 (4a).
Figure 7: Proposed biogenesis of 4a starting from the hypothetical precursor 3-ox with an acyclic sesquiterpe...
Figure 8: Hypothetical biogenesis of the bicyclic sesquiterpenoid moiety from the acyclic precursor of the si...
Graphical Abstract
Figure 1: a) Structure of borrelidin (1); b) PKS intermediates are attached to an acyl carrier protein domain...
Scheme 1: Retrosynthetic analysis of surrogate substrates for BorDH3 and reference molecules for enzyme assay...
Scheme 2: Synthesis of the common precursor aldehyde 11. Compound 13 was prepared in six steps and with an ov...
Scheme 3: Synthesis of the BorDH3 substrates. a) Thiophenolpropionate, Cy2BCl, Me2EtN, Et2O, −78 °C to −20 °C...
Scheme 4: Synthesis of reference compounds for the BorDH3 assay. a) 24, CH2Cl2, 50 °C, 3 h (88% over two step...
Graphical Abstract
Figure 1: Microginin (1) and (2S,3R)-AHDA (2a).
Scheme 1: Retrosynthetic analysis of AHDA.
Scheme 2: Synthesis of AHDA 2a.
Scheme 3: Synthesis of ent-AHDA 2b.
Graphical Abstract
Figure 1: Originally proposed structures A and B and revised structures 1 and 2 of putative sex pheromone com...
Scheme 1: Application of the iterative conjugate addition protocol for the preparation of 8.
Scheme 2: Deoxygenation and desilylation of 8.
Scheme 3: Vinylogous Horner–Wadsworth–Emmons olefination.
Scheme 4: Synthesis of α,β-unsaturated ester 15 using a Wittig reaction.
Scheme 5: Completion of the synthesis of the putative sex pheromone 2.
Graphical Abstract
Figure 1: Published 70 eV EI mass spectra of the naturally occurring compounds A and B [12].
Figure 2: Synthesis of tetramethyltrideca-2,4-dienes 8, 14 and 15. Conditions: a: LiAlH4, Et2O, −30 °C to rt,...
Figure 3: 70 eV EIMS of synthetic tetramethyltrideca-2,4-dienes 8, 14 and 15. These spectra were run under th...
Figure 4: Synthesis of (2E,4EZ)-syn,syn-4,6,8,10-tetramethyltrideca-2,4-diene (22), as well as (2E,4E)- and (2...
Graphical Abstract
Figure 1: Structures of muraymycins A1, B6, C1 and D1 1a–d.
Scheme 1: Synthesis of stereoisomerically pure amino alcohol 5 [32] and of derivative 6 suitable for X-ray crysta...
Figure 2: Molecular structure of levulinyl ester 6. Anisotropic displacement parameters are depicted at the 5...
Scheme 2: Synthesis of (2S,3S)-3-hydroxyleucine building blocks 13a,b useful for N-derivatization and of the ...
Scheme 3: Synthesis of (2S,3S)-3-hydroxyleucine building block 19 useful for C-derivatization and of aldehyde ...
Scheme 4: Synthesis of O-acylated (2S,3S)-3-hydroxyleucine derivatives 27 and 28.
Scheme 5: Synthesis of 6-methylheptanoic acid (26).
Scheme 6: Synthesis of Fmoc-protected building blocks 38 and 41 suitable for SPPS, with late-stage side chain...
Graphical Abstract
Figure 1: Known heronapyrroles A–C and nitropyrrolins A–E.
Scheme 1: Plausible biosynthesis of heronapyrroles A–D.
Scheme 2: Synthesis of heronapyrrole D.
Graphical Abstract
Figure 1: Immediate heme surroundings shown for the nearest relative of CYP154E1 with available crystal struc...
Scheme 1: Terpene substrates (grey background) and their oxidised derivatives.
Scheme 2: a) Ac2O, pyridine, room temperature, 24 h; b) SeO2, t-BuOOH, CH2Cl2, 0 °C, 5 h; c) K2CO3, MeOH, roo...
Scheme 3: a) SeO2, t-BuOOH, CH2Cl2, 0 °C, 3.5 h.
Graphical Abstract
Figure 1: Alkaloids produced by Streptomyces strain FORM5.
Figure 2: Part of the total ion chromatogram of the headspace extract of Streptomyces sp. FORM5 with the stru...
Figure 3: Mass spectra of a) (E)-2-(pent-3-en-1-yl)pyridine (streptopyridine E, 8), b) (1Z,3E)-penta-1,3-dien...
Scheme 1: Synthesis of streptopyridines A to E (8–12) and the 2-alkylpyridines 6 and 7.
Figure 4: Total ion chromatograms of the product mixtures of isomers 9–12 synthesized under E-selective (a) a...
Figure 5: Structures of piperidine derivatives 20–26.
Figure 6: a) Mass spectrum of streptopyridine A (12), b) mass spectrum of 12 after feeding of 2 mM 13C2-sodiu...
Scheme 2: Proposed biosynthesis of the streptopyridines. PKS: polyketide synthase; red: reduction; ta: transa...
Figure 7: Compounds detected in the headspace of Streptomyces sp. FORM5.
Graphical Abstract
Figure 1: Structures of cyclopamine (1) and carbacyclopamine analog 2.
Scheme 1: Retrosynthetic analysis of carbacyclopamine analog 2.
Scheme 2: Synthesis of carbacyclopamine analog 2.
Graphical Abstract
Figure 1: TDA and related natural products from Phaeobacter inhibens.
Scheme 1: Synthesis of tropone-2-carboxylic acid (13).
Scheme 2: Synthesis of halogenated TDA analogues.
Scheme 3: Further compounds included in this SAR study.
Graphical Abstract
Figure 1: Structure of sacrolide A (1).
Figure 2: Selected COSY (bold lines) and HMBC (arrows) correlations for sacrolide A (1).
Scheme 1: Initial derivatization strategy for the stereochemical analysis of sacrolide A (1).
Scheme 2: Determination of the stereochemistry of sacrolide A (1).
Scheme 3: Plausible biosynthesis of sacrolide A (1).
Figure 3: The effect of sacrolide A (1) on 3Y1 rat fibroblastic cells. (a) Control. (b) 45 min after exposure...
Figure 4: Extracted ion chromatograms for sacrolide A (1) molecular ion at m/z 307 [M – H]− in the LC–MS anal...