Asymmetric synthesis of (S)-homocitric acid lactone

Starting from (S)-phenylalanine, an asymmetric synthesis of (S)-homocitric acid lactone was achieved using Seebach’s SRS methodology. An intermediate for the synthesis of the (S)-per-homocitric acid lactone has also been synthesized.     

Stereoselective synthesis of (+)-boronolide and (−)-5-epi-boronolide

Stereoselective synthesis of boronolide and 5-epi-boronolide was achieved from d-(−)-tartaric acid. The key step involves the reduction of a keto Weinreb amide for the synthesis of boronolide, and a single pot construction of a diketone from the bis-Weinreb amide of tartaric acid and subsequent reduction with L-Selectride for 5-epi-boronolide.     

Stereoselective synthesis of (−)-microcarpalide

A stereoselective approach for the synthesis of the bio-active decanolactone (−)-microcarpalide was achieved from chiral pool tartaric acid. The synthesis of pivotal intermediates en route to the decanolactone was achieved from α-benzyloxy aldehydes derived from l- and d-tartaric acid.     

The synthesis of certain 11,14-dimethoxydeoxypodocarpic acid derivatives. an application to the synthesis of (+)-winterin from drimys winteri

This paper reports the synthesis of several 11,14-dimethoxydeoxypodocarpic acid derivatives from (+)-podocarpic acid. The synthesis of the naturally occurring sesquiterpene, (+)-winterin, from Drimys winteri illustrates a synthetic application of the 11,14-dimethoxy intermediates and establishes the absolute configuration for winterin.     

Direct synthesis of p-nitrobenzoic acid and benzoic acids from benzyl ketones and acetophenones using the CAN/HOAc system

The synthesis of p-nitrobenzoic acid and benzoic acids from benzyl and methyl ketones has been described using cerium(IV) ammonium nitrate in acetic acid. This simple method for the oxidation of benzylic ketones can be used as a practical method for the synthesis of 4-nitrobenzoic acid.     

Efficient enantiospecific synthesis of ent-conduramine F-1

An efficient enantiospecific total synthesis of ent-conduramine F-1 (aminocyclohexenetriol) was accomplished starting from the bis-Weinreb amide of tartaric acid. Key reactions in the synthesis include the desymmetrization of tartaric acid amide with vinylmagnesium bromide and installation of the required amine using Ellman sulfinimine. Ring closing metathesis was used to synthesize the required alkene in the cyclohexene.     

Asymmetric total synthesis of (+)-carneic acid A and structure revision of its natural form

This Letter describes the asymmetric total synthesis of (+)-carneic acid A via the stereoselective IMDA reaction of (E,E,E)-triene, which was prepared from the commercially available methyl (S)-3-hydroxy-2-methylpropionate. By this asymmetric total synthesis, we verified that the reported absolute structure of naturally occurring carneic acid A must be revised.     

Chemical and microbiological syntheses of intermediates in gibberellin biosynthesis

A partial synthesis of kaurenoic acid 1 from the hydroxy acid 3 is described. The hydroxylation of the 2′-carboxyethyl ester of 1 by Gibberella fujikuroi has been utilized for the synthesis of 7β-hydroxykaurenoic acid 2. An alternative synthesis of 2 is provided by the microbiological conversion of 3 to the 7β-hydroxy derivative by Calonectria decora.     

Naturstoffchemie. 108. Mitt. Synthese des 7,7′-Oxy-dicumarins,dem möglichen Präkursor vom Lasioerin und Gnidicumarin

The synthesis of 7,7′-oxy-dicoumarin from 7-hydroxycoumarin and 7-bromocoumarin viaUllmann synthesis is described. In contrast to the literature, from the reaction ofm-bromophenol with 2-hydroxy succinic acid, 7-bromocoumarin as well as 5-bromocoumarin were obtained.     

Heck-mediated synthesis and photochemically induced cyclization of [2-(2-styrylphenyl)ethyl]carbamic acid ethyl esters and 2-styryl-benzoic acid methyl esters: total synthesis of naphtho[2,1f]isoquinolines (2-azachrysenes)

We describe two new closely related total syntheses of naphtho[2,1-f]isoquinolines. The first synthesis consists of a Heck coupling reaction between trifluoromethanesulfonic acid 2-(2-ethoxycarbonylaminoethyl)phenyl esters and styrenes to give [2-(2-styrylphenyl)ethyl]carbamic acid ethyl esters. These compounds cyclize to give (2-phenanthren-1-yl-ethyl)carbamic acid ethyl esters, from which 2-azachrysenes can be obtained in a three-step sequence. The second synthesis includes a new total synthesis of 2-styrylbenzoic acid methyl esters by Heck coupling of methyl o-iodobenzoates to styrenes, followed by the transformation of the resulting benzoic acid derivatives into phenanthrene-1-carboxylic acid methyl esters and then into the target compounds by a six-step sequence including a Bischler-Napieralski cyclization.     

Total synthesis of 6-epiprelactone-V via a syn-selective oxygen tethered intramolecular Michael reaction

The intramolecular protective group (benzylidene acetal) assisted syn-1,3-diol synthesis has been efficiently utilized in a short synthesis of 6-epiprelactone-V starting from (S)-malic acid.     

Stereocontrolled total synthesis of (+)-pederine

A mild one-pot method for the synthesis of acyclic N-(1-methoxyalkyl)amides starting from carboxylic acid and methyl imidates has been developed and applied to the first total synthesis of (+)-pederine (1), a potent insect poison. Furthermore, the stereocontrolled total synthesis of 1 was also achieved by employing acid catalyzed double alkoxy-exchange reaction of N-(1 -methoxylakyl)amide group as key step.     

A convenient formal synthesis of (2S,3S)-3-hydroxy pipecolic acid

A convenient synthesis of (2S,3S)-3-hydroxy pipecolic acid starting from inexpensive and easily available l-(+)-tartaric acid has been described.     

Short and efficient synthesis of (+)-subersic acids

An efficient synthesis of (+)-subersic acid, the unnatural enantiomer, has been achieved from sclareol and p-hydroxybenzoic acid.     

A simple, novel and convenient method for the synthesis of 1-aminophosphinic acids: synthesis of a novel C2-symmetric phosphinic acid pseudodipeptide

A simple, efficient and novel method has been developed for the synthesis of 1-aminophosphinic acids from simple starting materials. Treatment of aromatic aldehydes with ammonia and hypophosphorus acid gives novel C₂-symmetric 1-aminoarylmethylphosphinic acids. The synthesis of novel C₂-symmetric phosphinic acid pseudodipeptides is also discussed.     

Facile synthesis of Fmoc-N-methylated α- and β-amino acids

A highly efficient and environmentally friendly synthesis of Fmoc-N-methyl α- and β-amino acids from the corresponding Fmoc-amino acid, via intermediate oxazolidinones/oxazinanones, has been developed. Microwave heating for 3 min was required for the synthesis of the oxazinanones, while their Lewis acid catalyzed reductive opening only needed 1 min for completion. Hence, Fmoc-N-methyl-amino acids, suitable for, for example, solid phase peptide synthesis, can be readily prepared from the corresponding Fmoc amino acid in less than 1 h including purification. Fmoc-β³-homophenyl alanine showed unanticipated reactivity, and provided a one-step route to the highly useful Fmoc-protected 1,2,3,4-tetrahydroisoquinolineaceticacid, that is a β-hTic analogue.     

A convenient and new approach to the synthesis of ω-heterocyclic amino acids from carboxy lactams through ring-chain-transformation. Part 2: Synthesis of (2R)-/(2S)-2-aminomethyl-3-(1-aryl-/1,5-diaryl-1H-pyrazol-3-yl)-propionic acid

Making use of amide activation, a convenient and short path synthesis of optically pure ω-heterocyclic-β-amino acids has been achieved from (1R,3R)- and (1R,3S)-5-oxo-1-(1-phenyl-ethyl)-pyrrolidine-3-carboxylic acid methyl ester. The key step of the synthesis involves a regiospecific ring-chain-transformation of the enaminones when subjected to 1,2-binucleophilic attacks. The method is illustrated by the synthesis of (2R)-/(2S)-2-aminomethyl-3-(1-aryl-/1,5-diaryl-1H-pyrazol-3-yl)-propionic acid.     

Efficient resolution of rac-2-cyano-2-methyl-3-phenylpropanoic acid. An appropriate starting material for the enantioconvergent synthesis of (S)-α-methylphenylalanine on a large laboratory scale

A large laboratory scale synthesis of (S)-α-methylphenylalanine from benzaldehyde and methyl cyanoacetate has been developed. The synthesis is based on the following sequence: (i) preparation of racemic 2-cyano-2-methyl-3-phenylpropanoic acid, (ii) resolution of the enantiomers by crystallisation using norephedrine, and (iii) development of an efficient enantioconvergent synthesis of (S)-α-methylphenylalanine from enantiopure (S)- and (R)-2-cyano-2-methyl-3-phenylpropanoic acid. The simplicity of the experimental procedures, which avoid low temperature reactions, the need for an inert atmosphere and column chromatography, combined with the use of inexpensive and readily available reagents make this method synthetically very attractive.     

Synthesis of protected (2R,3R,4S)-4,7-diamino-2,3-dihydroxyheptanoic acid, a constituent of callipeltins A and D

An efficient synthesis of protected (2R,3R,4S)-4,7-diamino-2,3-dihydroxy heptanoic acid, a constituent of the depsipeptides, callipeltins A and D from l-ascorbic acid is described.     

Synthesis of homochiral tetrahydropteridines

A synthesis of protected homochiral tetrahydropteridines from (2S)-malic acid has been developed. This presents methodology for the synthesis of reduced pteridine coenzymes and pharmaceuticals.