Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization

• Senze Qiao,
• Zhongyu Cheng and
• Fuzhuo Li

Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66

• pikromycin and the aglycones in this family, 10-deoxymethynolide (24) and norbonolide (25), using asymmetric aldol reaction, Yamaguchi esterification, and ring-closing metathesis as key steps [65][66]. Nevertheless, the inherent complexity of these natural products demands high step counts, leading to low

Evaluation of the enantioselectivity of new chiral ligands based on imidazolidin-4-one derivatives

• Jan Bartáček,
• Karel Chlumský,
• Jan Mrkvička,
• Lucie Paloušová,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2024, 20, 684–691, doi:10.3762/bjoc.20.62

• also tested in asymmetric aldol reactions. Under the optimised reaction conditions, aldol products with enantioselectivities of up to 91% ee were obtained. Keywords: asymmetric aldol reaction; asymmetric Henry reaction; chiral ligands; enantioselective catalysis; imidazolidine derivatives

• with reduced efficiency in the absence of a second stereogenic centre at position 5. Nonetheless, IV proved to be an effective enantioselective organocatalyst in the asymmetric aldol reaction, matching the enantioselectivity levels of other proline-heterocycle derivatives [25]. Overall, our findings

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• (−)-irofulven (87), Movassaghi et al. used a CuII-catalyzed asymmetric aldol reaction of O-silyl ketene S,O-acetal 84 with methyl pyruvate (85) to enantioselectively install the crucial tertiary TMS-protected alcohol in ester 86 (Scheme 14) [29]. Eleven further steps gave (−)-irofulven (87). 2. Mesoxalic

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• phosphonate reagent 50 proceeded stereoselectively to give ester 51 in excellent yield (94%). Subsequent DIBAL-H reduction of ester 51 followed by tetrapropylammonium perruthenate (TPAP) oxidation afforded aldehyde (Z,E)-52 as a single isomer in 83% yield over two steps. The asymmetric aldol reaction aldehyde

• ). The total synthesis of inthomycin C ((+)-3) was achieved by using a Stille coupling between (E,E,)-67 and vinyl iodide 48 followed by directed asymmetric aldol reaction under Mukaiyama–Kiyooka aldol reaction conditions (Scheme 6). Initially, (E)-3-(tributylstannyl)propenal (65) was converted into (E,E

• asymmetric aldol reaction in the presence of oxazaborolidinone derivative 68 and silyl ketene acetal 53 to produce the required α-hydroxy ester (+)-11 in 50% yield and 76% ee ((R)-stereochemistry of the major enantiomer). A competitive reduction of 71 was also observed to produce alcohol 72 in 43% yield

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• inexpensive and easily available. The work of List and Barbas in 2000 was groundbreaking for L-proline-catalyzed reactions [40]. They published a L-proline-catalyzed asymmetric aldol reaction and suggested that the essential catalytic step is the enamine formation between the secondary amine function of L

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• asymmetric aldol reaction of cyclohexanone and 4-nitrobenzaldehyde [83]. Cross-linked polymersome nanoreactors were also used to perform asymmetric cyclopropanation reactions in water [15]. These products are highly desired intermediates in the preparation of agrochemicals and pharmaceuticals [84][85][86

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• -free conditions were performed using a combination of (S)-binam-L-Pro (A, 5 mol %) and benzoic acid (10 mol %) as organocatalyst [49]. Juaristi and co-workers investigated the mechanistic aspects of α,α-dipeptide derivatives of a (S)-proline- (A′)-catalyzed asymmetric aldol reaction (Scheme 2b) under

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• products in good yields and with excellent enantioselectivities (Scheme 16). In 2013, Ishimaru and co-workers developed a N-aryl-L-valinamide (cat. 5)-catalyzed asymmetric aldol reaction of isatins with ketones, affording the products in excellent yields and with up to >99% ee (Scheme 17) [33]. The

• reaction was performed under mild conditions using PTSA·H2O as the additive. Subsequently, the asymmetric aldol reaction of aliphatic aldehydes with isatins was achieved by the same group by using a structurally slightly modified organocatalyst (cat. 5, Scheme 18) [34]. Malonic acid as the additive and

• asymmetric aldol reaction of trifluoromethyl α-fluorinated β-keto gem-diols with isatins, generating 3-hydroxyoxindoles in high yields (up to 99%) and with excellent enantioselectivities (up to 98% ee, Scheme 28) [45]. The reaction was performed at room temperature using AcOH as the additive in the presence

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• of organic reactions, such as the direct asymmetric aldol reaction, one of the most important C–C bond-forming reactions in organic synthesis [51]. The currently accepted mechanism suggests a central enamine intermediate which forms a Zimmerman–Traxler-like transition state with the acceptor

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

• the known allylic alcohol [58]. To synthesize ketone 57, we opted to utilize an asymmetric aldol reaction to set the stereochemistry of the β-hydroxy group. Since the report of Evans’s diastereoselective asymmetric aldol reaction using the boron enolates of N-acyloxazolidinones [59], numerous chiral

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• , viz. ball-milling and grinding with pestle and mortar. Review Aldol reaction Since the origin of organocatalysis, the asymmetric aldol reaction has been one of the most intensely studied reactions, providing an easy access to chiral β-hydroxycarbonyl compounds, which are important building blocks for

• -milling over traditional stirring in terms of reaction rate, product yield, and stereoselectivity was observed. In 2011, Hernández and Juaristi utilized the catalytic potential of α,α-dipeptide, i.e., methyl ester of (S)-proline-(S)-phenylalanine (III) for organocatalytic asymmetric aldol reaction of

• co-workers reported a highly efficient asymmetric aldol reaction of cyclic ketones with various aromatic aldehydes catalysed by a new series of (S)-proline containing thiodipeptides under solvent-free HSBM conditions (Scheme 5) [38]. The thiodipeptide V catalyses the stereoselective formation of

Can we measure catalyst efficiency in asymmetric chemical reactions? A theoretical approach

• Shaimaa El-Fayyoumy,
• Matthew H. Todd and
• Christopher J. Richards

Beilstein J. Org. Chem. 2009, 5, No. 67, doi:10.3762/bjoc.5.67

• asymmetric hydrogenation, which gives a product of 79% ee, is employed in the industrial multi-tonne synthesis of (S)-metolachlor [3]. An instructive comparison may be made between an antibody capable of catalysing an intramolecular, asymmetric aldol reaction and proline, capable of catalysing the same

Stereoselective synthesis of (2S,3S,4Z)-4-fluoro- 1,3-dihydroxy- 2-(octadecanoylamino)octadec- 4-ene, [(Z)-4-fluoroceramide], and its phase behavior at the air/water interface

• Gergana S. Nikolova and
• Günter Haufe

Beilstein J. Org. Chem. 2008, 4, No. 12, doi:10.3762/bjoc.4.12

• fatty acid amide functions. Results In a short synthetic route (2S,3S)-4-fluorosphingosine and 4-fluoroceramide, the fluorinated analogues of the natural products, D-erythro-sphingosine and ceramide, have been prepared. The key step of the synthetic sequence is an asymmetric aldol reaction of (Z)-2

• formation of multi-layers was observed for natural ceramide. Conclusions Asymmetric aldol reaction proved to be successful for the preparation of enantiopure 4-fluoroceramide. Surface/pressure isotherms and hysteresis curves of ceramide and its 4-fluoro derivative showed that the presence of fluorine leads

• recently for the preparation of long chain α-fluoro-α,β-unsaturated carboxylic acid esters [29] and fluorinated 2,4-dienecarboxylic acid esters [30]. The key step of the synthesis is an asymmetric aldol reaction of the fluorinated aldehyde 3 with the enantiopure iminoglycinate 4 (Scheme 1). The latter