Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• reviewed, including the phosphonylation of hydroxy esters with phosphonochloridates, the condensation of phosphonic monoesters and hydroxy esters, the alkylation of phosphonic monoesters with 1-(alkoxycarbonyl)alkyl halides or sulfonates, multicomponent condensation of amides, aldehydes, and

• dichlorophosphites followed by alcoholysis with hydroxy esters, the phosphinylation of hydroxy esters with phosphonochloridites followed by oxidation, and the carbene insertion of N-protected amino acids with 1-diazoalkylphosphonates. This review includes the synthesis of α-, β-, and γ-phosphonodepsipeptides and

• phosphonylation of hydroxy esters 2 with N-protected aminoalkylphosphonochloridates 3 (method I), reactions of N-protected aminoalkylphosphonic monoesters 4 with hydroxy esters 2 (method II) or with 1-(alkoxycarbonyl)alkyl halides or sulfonates 5 (method III), pseudo-four-component condensations (method IV), and

3-Acetoxy-fatty acid isoprenyl esters from androconia of the ithomiine butterfly Ithomia salapia

• Florian Mann,
• Daiane Szczerbowski,
• Lisa de Silva,
• Melanie McClure,
• Marianne Elias and
• Stefan Schulz

Beilstein J. Org. Chem. 2020, 16, 2776–2787, doi:10.3762/bjoc.16.228

• catalysis [33]. Final acetylation of the hydroxy esters delivered the target compound isoprenyl 3-acetoxyoctadecanoate (11). Comparison of mass spectra and retention index confirmed the identity of the naturally occurring compound and 11. An enantioselective synthesis of isoprenyl (Z)-3-acetoxyoctadec-13

• because of the high elution temperatures needed, we reasoned that the respective methyl 3-hydroxy esters would be much better suited, given the well-known separability of these compounds by chiral GC [35]. Therefore, a natural extract of the androconia and synthetic (R)-12 were transesterified with NaOMe

• eicosanoate and isoprenyl 13-eicosenoate, determined by DMDS derivatization. Next to these major esters, minor amounts of related esters occurred in some samples. These include deacylated 3-hydroxy esters, isoprenyl 3-hydroxyoctadecenoates and 3-hydroxyoctadecanoate, occurring in group C. Finally, respective

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• afforded the α-hydroxy esters 166a,b. Dess–Martin oxidation [79][80] of the latter, followed by hydrolysis of the ester gave keto acids 167a,b. Finally, the reductive amination of 167a,b with 25% aqueous ammonia and NaBH4 afforded the racemic β,β-difluorophenylalanine derivatives 168a,b in 67% yield [81

• 152. Synthesis of β-fluorophenylalanine derivatives from α- or β-hydroxy esters 152a and 155. Synthesis of a series of β-fluoro-Phe derivatives via Pd-catalyzed direct fluorination of β-methylene C(sp3)–H bonds in Phe substrates functionalized with the PIP auxiliary group. Synthesis of series of β

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• electrocatalytic hydrogenation of α-keto esters 12 to afford corresponding hydroxy esters 13b and 13c with appreciable enantioselectivities (Scheme 6). Following the pioneering works by Grimshaw et al. [28] in 1973, Gileadi and co-workers showed that the addition of quinidine or related alkaloids to the reaction

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• -butyl)borohydride (ʟ-Selectride). The syn-β-fluoro-α-hydroxy esters were obtained finally in good yields with excellent enantioselectivities (83–95% ee). There are two examples of a Pd-catalyzed fluorination of oxindoles. In 2012, Shi and co-workers [41] described the enantioselective asymmetric

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

• Juanjuan Feng,
• Tianyu Li,
• Jiaxin Zhang and
• Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

• could be prepared from enantiomerically pure β-hydroxy ketones through β-hydroxy-directed carbonyl reduction following Evans’ [3] or Prasad’s [4][5][6][7][8][9][10][11] method. The Narasaka–Prasad reduction of a δ-hydroxy-β-keto esters derived from β-hydroxy esters [12][13][14][15][16][17][18][19][20

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• . The synthesis of photoreactive tripeptide analogues incorporating photo amino acids 4–6 will be explored thereafter. Actin-binding cyclodepsipeptides, photo amino acids, retrosynthetic cuts of polyketide 7 leading to organozinc compound 8. Synthesis of γ-hydroxy esters 11 and 12, followed by Mitsunobu

Synthesis and biological investigation of (+)-3-hydroxymethylartemisinin

• Toni Smeilus,
• Farnoush Mousavizadeh,
• Johannes Krieger,
• Xingzhao Tu,
• Marcel Kaiser and
• Athanassios Giannis

Beilstein J. Org. Chem. 2019, 15, 567–570, doi:10.3762/bjoc.15.51

• -hydroxy esters 9, 10 and 11 (dr = 1.74:0:38:0.24) in a total yield of 84% (Scheme 2). Gratifyingly, the percentage of derivatives 9 and 10 that show the desired stereochemistry at carbon center 5a is around 90%. The structure of all these isomers was confirmed by NOE experiments (see Supporting

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• reactions which were applied to α-hydroxy esters 74 and 75 using N-iodosuccinimide (MeCN/H2O, 50 °C) [70], or to the N-benzylamine generated from α-amino ester 71 (by reductive animation with benzaldehyde) in the presence of I2 and K2CO3 (MeCN, rt) [71]. These iodocyclizations led to the oxabicyclic

Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

• Zhengning Li,
• Chongnian Wang and
• Zengchang Li

Beilstein J. Org. Chem. 2015, 11, 213–218, doi:10.3762/bjoc.11.23

• mainly based on the lactonization of γ-hydroxy esters, which were obtained through either addition of substituted succinate-derived enolates to carbonyls [3][4][5][6][7], or direct reduction of the corresponding γ-keto esters [8]. Usually they were carried out under acidic or basic conditions, which are

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids

• Zhiqiang Duan,
• Jianlin Han,
• Ping Qian,
• Zirui Zhang,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 969–974, doi:10.3762/bjoc.10.95

• University, Nanjing, 210093, China 10.3762/bjoc.10.95 Abstract We show a convenient decarboxylative aldol process using a scandium catalyst and a PYBOX ligand to generate a series of highly functionalized chiral α-hydroxy esters. The protocol tolerates a broad range of β-keto acids with inactivated aromatic

• and aliphatic α-keto esters. The possible mechanism is rationalized. Keywords: enantioselective synthesis; hydroxy esters; scandium; Introduction The catalytic enantioselective construction of tertiary carbon centres is a major challenge in organic chemistry. The nucleophilic attack of carbonyls

• ). We presume that relatively hindered α-keto esters could also be engaged as aldehydes in the decarboxylative aldol reactions with β-keto acids, which would provide a practical and efficient route to access α-hydroxy esters in an enantioseletive fashion (Figure 3). Results and Discussion By

Unusual polymorphism in new bent-shaped liquid crystals based on biphenyl as a central molecular core

• Anna Kovářová,
• Svatopluk Světlík,
• Václav Kozmík,
• Jiří Svoboda,
• Vladimíra Novotná,
• Damian Pociecha,
• Ewa Gorecka and
• Natalia Podoliak

Beilstein J. Org. Chem. 2014, 10, 794–807, doi:10.3762/bjoc.10.75

• intermediate hydroxy esters 14–16 were finally acylated with acids 6a–c utilizing the DCC/DMAP method to yield the target compounds of series I–III. Series of materials IV–VI were obtained in a very similar manner starting with acid 2 (Scheme 2). In the first step, acid 2 was coupled (DCC/DMAP) with phenols 7a

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• the preparation of certain families of tertiary thiols and thioethers. For example, SN2 displacement of a mesylate leaving group by thiophenol can be accomplished using α-hydroxy esters 2 (Scheme 1) [12]. The presence of the α-ester group of 3 promotes SN2 reaction in two ways: The electron

• -withdrawing nature of the substituent inhibits SN1 dissociation and carbocation formation, and the planar ester group poses minimal steric hindrance towards approach of the nucleophile. Yields of substitution in α-aryl-α-hydroxy esters 5 are poor with a significantly decreased enantiomeric ratio in the

• . The use of α,α-dialkyl hydroxy esters 8 is more successful: Thioethers 10 are formed in high yield and with almost complete stereospecificity (Scheme 3). Using the same principles of low steric bulk and electronic inhibition of the SN1 reaction pathway, α-(sulfonyloxy)nitriles, easily prepared from

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• desired alkylated alkynes 117 in high yields and excellent anti diastereoselectivities of up to 99 : 1 d.r. (Scheme 43) [117]. Treatment of chiral β-hydroxy esters with aromatic and aliphatic nitriles in the presence of catalytic amounts of TfOH and subsequent hydrolysis in a Ritter-type reaction led to

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• standard procedure, [3] and used to tether our allylsilane to the hydroxyl groups of both syn- and anti-β-hydroxy esters, 9a and 8b, by simply stirring the two reagents in the absence of solvent (Scheme 7). The by-product from this reaction is Et2NH, which can be easily removed by evaporation under reduced

• relative stereochemistry. Retrosynthesis of aldehyde anti-4. Attempts to reduce the bulky aryl ester resulted in Si-O bond cleavage and over-reduction to the primary alcohol. Preparation of syn- and anti-β-hydroxy esters. Preparation of the syn- and anti-aldehyde cyclisation precursors 4. Intramolecular