Decandrinin, an unprecedented C₉-spiro-fused 7,8-seco-ent-abietane from the Godavari mangrove Ceriops decandra

• Hui Wang,
• Min-Yi Li,
• Félix Zongwe Katele,
• Tirumani Satyanandamurty,
• Jun Wu and
• Gerhard Bringmann

Beilstein J. Org. Chem. 2014, 10, 276–281, doi:10.3762/bjoc.10.23

• shown in Figure 4. A plausible biogenetic precursor of decandrinin (1) might be the naturally more common β-diastereomer of 7,13-ent-abietadien-3-ol (2). Accordingly, its 3β-OH group would be oxidized to yield int A, whose C-9 would then be hydroxylated to afford int B. Oxidative cleavage at the ∆7,8

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• 96, for which the yield and enantioselectivity was determined starting from 93. Standard functional group interconversion first provided exo-methylene 97, followed by ruthenium-catalyzed oxidative cleavage of the installed exo-methylene moiety [94] to give tricyclic ketone 98, which can be converted

• quarternary carbon center, the resulting amide cyclized during the purification on silica to give amide 174. Reduction of this amide to the aminal was followed by dehydration and Lemieux–Johnson [149] oxidative cleavage to give dialdehyde 175. The liberated alcohol moiety was reprotected, followed by cleavage

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• assembled from nine acetate units and glycine, respectively N-methylglycine derivative, which contributes both carbon atoms and the nitrogen to the skeleton of 210 (position 12 and 12a). The latter are uncommon starter units in a type II polyketide assembly line [160]. Upon oxidative cleavage of the D-ring

A practical synthesis of long-chain iso-fatty acids (iso-C₁₂–C₁₉) and related natural products

• Mark B. Richardson and
• Spencer J. Williams

Beilstein J. Org. Chem. 2013, 9, 1807–1812, doi:10.3762/bjoc.9.210

• triethylsilane and BF3·Et2O [53], affording 11. Oxidative cleavage of 11 with KMnO4/Bu4NBr [54] afforded iso-C12 acid 1. Alternatively, anti-Markovnikov hydration of 11, using I2/NaBH4 then hydrogen peroxide [55], afforded the alcohol 12, and oxidation of 12 with KMnO4/Bu4NBr afforded iso-C13 acid 2

• ] followed by Chugaev elimination afforded the terminal alkene 19. Oxidative cleavage of 19 using KMnO4/Bu4NBr [54] afforded iso-C16 acid 5. Reduction of 5 (BH3·Me2S) [59] afforded the alcohol 20 that when subjected to the same transformations as before, via the xanthate ester 21, delivered the terminal

• alkene 22. Finally, oxidative cleavage (KMnO4/Bu4NBr) [54] of 22 afforded iso-C15 acid 4. The iso-C18 7 and iso-C19 8 fatty acids were synthesized through similar approaches from the related C16 lactone hexadecanolide 23 [60] (Scheme 3). Reaction of 23 with methylmagnesium bromide afforded 24

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• material throughput. In order to proceed with the synthesis, we needed a more robust route, with the following criteria: (1) no protecting groups requiring oxidative cleavage, and (2) introduction of the C13 hydroxy group at an early stage. Iodocyclization approaches to epoxide In the preparation of model

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• decreased from 24.5 to 21.3%. Very recently NHPI was reported to catalyze selective transformations without requiring additional initiators. Jiao et al. described the catalyzed oxidative cleavage of C=C double bonds using molecular oxygen as the final oxidant [72]. Following this approach α-methylstyrene

• from N-alkoxyphthalimides. Visible-light/g-C3N4 induced metal-free oxidation of allylic substrates. NHPI/o-phenanthroline-mediated organocatalytic system. NHPI/DMG-mediated organocatalytic system. NHPI catalyzed oxidative cleavage of C=C bonds. Synthesis of hydrazine derivatives. Acknowledgements We

Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation

• Lynnie Trzoss,
• Jing Xu,
• Michelle H. Lacoske and
• Emmanuel A. Theodorakis

Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126

• (0)-catalyzed carbomethoxylation [87][88][89][90] produced the desired C-ring lactone 20 in 61% yield. Epoxidation of the C-6/C-7 enone with NaOH/H2O2 followed by oxidative cleavage of the C-11 terminal alkene under OsO4/NaIO4 conditions [91][92] afforded the corresponding C-11 aldehyde. Exposure of

Development of peptidomimetic ligands of Pro-Leu-Gly-NH₂ as allosteric modulators of the dopamine D₂ receptor

• Swapna Bhagwanth,
• Ram K. Mishra and
• Rodney L. Johnson

Beilstein J. Org. Chem. 2013, 9, 204–214, doi:10.3762/bjoc.9.24

• accomplished by initial esterification of 33a and 33b, respectively, followed by oxidative cleavage of the double bond in each case with OsO4/NaIO4 [46]. An efficient and reproducible conversion of 33b into 34c was developed that consisted of the following three-step route: (1) benzyl ester formation, (2

• ) oxidative cleavage of the double bond with OsO4/NaIO4, and (3) hydrogenolysis of the benzyl ester [36][48]. Although the Seebach methodology provides a highly stereoselective way to α-alkylated prolines, there are several shortcomings to the originally developed protocols [47]. In the oxazolidinone

A Wittig-olefination–Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis

• Mukund G. Kulkarni,
• Mayur P. Desai,
• Deekshaputra R. Birhade,
• Yunus B. Shaikh,
• Ajit N. Dhatrak and
• Ramesh Gannimani

Beilstein J. Org. Chem. 2012, 8, 1725–1729, doi:10.3762/bjoc.8.197

• underwent Claisen rearrangement to give 4-pentenals 3a–h. Protection of the aldehyde group of the 4-pentenals as acetals 4a–h and subsequent oxidative cleavage of the terminal olefin furnished nitroaldehydes 5a–h. Reductive cyclization of these nitroaldehydes yielded the required 3-methylquinoline-4

• -carbaldehydes 6a–h in excellent yields. Therefore, an efficient method was developed for the preparation of 3-methylquinoline-4-carbaldehydes from o-nitrobenzaldehydes in a simple five-step procedure. Keywords: acetal; Claisen rearrangement; oxidative cleavage; ring-closure; Wittig olefination; Introduction

• unsuccessful. Subjecting these acetals to oxidative cleavage in aq THF furnished the aldehydes 5a–h in good yields (Table 1). The NMR of these aldehydes revealed them again to be a mixture of diastereomers, although they appeared to be homogeneous on TLC. Reductive cyclization of these nitroaldehydes furnished

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• fact, the furan ring can readily undergo oxidative cleavage under various conditions, thus providing an interesting route to carboxylates [35]. In the case of tpys, oxidation of the furanyl ring was performed by using potassium permanganate in a basic reaction medium, followed by acidification to

Directed aromatic functionalization in natural-product synthesis: Fredericamycin A, nothapodytine B, and topopyrones B and D

• Charles Dylan Turner and
• Marco A. Ciufolini

Beilstein J. Org. Chem. 2011, 7, 1475–1485, doi:10.3762/bjoc.7.171

• more electrophilic quinolyl ketone would direct an initial conjugate addition of the anion of a suitable cyanoacetamide to its own β-position. A particularly direct way to produce 41 seemed to be the oxidative cleavage of the furan ring in 42, which thus became the first subgoal of our study. In that

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

• Ameer F. Zahoor,
• Sarah Thies and
• Uli Kazmaier

Beilstein J. Org. Chem. 2011, 7, 1299–1303, doi:10.3762/bjoc.7.151

• by chelated enolate Claisen rearrangement [22][23] or transition metal-catalyzed allylic alkylation of chelated enolates [24] and subsequent oxidative cleavage of the γ–δ-unsaturated amino acids obtained. Results and Discussion An alternative approach is based on regioselective ring opening of

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• particular, water as a nucleophilic reagent has been used in the addition of alkynes and allenes [16][17][18]. In contrast, gold-catalyzed oxidation chemistry has been less well developed [25][26][27][28][29][30][31][32][33][34][35][36], although oxidative cleavage of carbon–carbon double bonds and carbon

• /hydration and oxidative cleavage of allenes to form α-diketones and aldehydes, and the synthesis of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine [45][46][47][48][49][50][51][52][53][54][55][56]. Results and Discussion Our initial

• of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine was achieved in high yields. This reaction appears to proceed via oxidation/hydration and oxidative cleavage of the allene, and investigations into the mechanism of this

Total synthesis of (±)-coerulescine and (±)-horsfiline

• Mukund G. Kulkarni,
• Attrimuni P. Dhondge,
• Sanjay W. Chavhan,
• Ajit S. Borhade,
• Yunnus B. Shaikh,
• Deekshaputra R. Birhade,
• Mayur P. Desai and
• Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

• in clean cyclization leading to oxindole 9. After protecting the amide nitrogen with Boc, the oxindole 10 was treated with NaH, followed by ethyl chloroformate at 0 °C to give 11 in 80% yield. Oxidative cleavage of the allyl group was accomplished by catalytic osmium tetroxide and N-methylmorpholine

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• to a tricarboxylic acid core. Keywords: aminopyrans; carbohydrate mimetics; Lewis acids; lithiated enol ethers; nitrones; oxidative cleavage; stereodivergent synthesis; Introduction The pyran structural motif can be found in numerous bioactive natural products. Possible strategies towards their

• enantiopure aminopyrans. An additional option for the use of the enol ether moiety is oxidative cleavage [21]. Thus, benzyl protection of compound cis-5b followed by treatment of the resulting 19 with RuCl3 and NaIO4 gave the ten-membered ring lactone 20 by selective cleavage of the internal double bond

• moiety of trans-5a leading to products 13–15. Bromination of bicyclic dihydropyran trans-5b affording 16. Synthesis of epoxypyran 18 by bromination of cis-5d. Oxidative cleavage of dihydropyran 19 to lactone 20. Transformation of α-bromoketone 15 into nitrone 21 by an internal redox reaction

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• 21 and oxidative cleavage of the resulting diol, the resultant aldehyde was treated with chiral allenylboronic ester to afford 22. The terminal epoxides 24 and 26 were prepared from the same intermediate 23. Coupling of 22 with 24 (or 26) in the same manner followed by hydrogenation and removal of

Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• -disubstituted pyrrolidine (Scheme 6). This transformation was of interest because the pyrrolidine ring is a common nitrogen-containing motif in natural products and pharmaceutically relevant molecules [33]. Ruthenium tetraoxide was first examined as a reagent for the oxidative cleavage of the aromatic ring

• –oxidation with (−)-Ipc2BH to be determined by chemical correlation. Pyrrolidine 35 was independently prepared from (1R)-(−)-2-azabicyclo[2.2.1]hept-5-en-3-one (Vince’s lactam [36], 37) via reduction with LiAlH4, Boc-protection and oxidative cleavage [37] (Scheme 9). The pyrrolidines prepared from rearranged

• azacycle (+)-8 and lactam 37 were both dextrorotatory, confirming the provisional assignment of configuration that had been made by analogy with Laschat’s work [29]. Since attempts to effect RuO4-mediated oxidative cleavage of 2-azabenzonorbornene 8 employing periodic acid as the stoichiometric co-oxidant

End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• ) by a Claisen rearrangment (via the silyl enol ether) was not high yielding and produced many side products. Ozonolysis of 25 afforded the acetone sidechain (i.e. 26) in acceptable yield (50%). Other methods to unmask the ketone functionality failed, for example, dihydroxylation followed by oxidative

• cleavage. Nevertheless, the acetone sidechain could be introduced in ~20% overall yield allowing end game functionalisation (as discussed below). α-Hydroxylation was next investigated. Considering the observed preference for regiospecific enolate formation in our system we devised a simple two pot

Total synthesis of the indolizidine alkaloid tashiromine

• Stephen P. Marsden and
• Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

• of the allylsilane to the N-acyliminium ion occurs through a chair-like transition state with the nascent alkene equatorially disposed. All that remained to complete the synthesis of tashiromine 1 was to effect the oxidative cleavage of the C5 vinyl substituent, then carry out a global reduction of

Combining two-directional synthesis and tandem reactions, part 11: second generation syntheses of (±)-hippodamine and (±)-epi-hippodamine

• Annabella F. Newton,
• Martin Rejzek,
• Marie-Lyne Alcaraz and
• Robert A. Stockman

Beilstein J. Org. Chem. 2008, 4, No. 4, doi:10.1186/1860-5397-4-4

• intermediate 7 and try to realise an improvement over our earlier work. This paper discloses two such improvements. The first of these is the conversion of dialkene 4 into the diacrylate derivative 6 . Originally this was achieved by oxidative cleavage of the two alkene moieties of 4 to form the rather

• immediately after isolation of the dialdehyde 5 (this was found to decompose upon storage, even at low temperature), and also the oxidative cleavage reaction produced large amounts of toxic osmium waste. During our recent synthesis of histrionicotoxin [11], we found that two-directional homologation of a

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• 6a (Scheme 2) with correct absolute configurations for castanospermine (C-8/C-8a), we sought to transform 6a into the target alkaloid, and in this paper report on the synthesis of an advanced intermediate towards this goal. Thus, adduct 6a underwent oxidative cleavage of the PMB protecting group

Do α-acyloxy and α-alkoxycarbonyloxy radicals fragment to form acyl and alkoxycarbonyl radicals?

• Dennis P. Curran and
• Tiffany R. Turner

Beilstein J. Org. Chem. 2006, 2, No. 10, doi:10.1186/1860-5397-2-10

• -butenylmagnesium bromide to 3-methylcyclohexenone followed by quenching with either acetyl chloride [26] or methyl chloroformate provided enol ester 9a (50%) and enol carbonate 9b (83%). Oxidative cleavage [27][28][29] and reduction then provided alcohols 10a and 10b, which were converted to iodides 11a and 11b