Cu(I)-catalyzed tandem benzyldiazoester coupling with terminal alkyne-allene formation-Michael reaction: application to the syntheses of oxa and azacycles

A simple and practical procedure for the synthesis of aza- and oxacycles, which possess an array of stereogenic functionalities, is described. This protocol relies on tandem Cu-catalyzed coupling of suitably functionalized terminal alkyne with diazoester followed by isomerization and subsequent aza or oxa-Michael reaction, thus generating the required scaffold with high diastereoselectivity.     

First stereoselective total synthesis of panaxjapyne C

The first stereoselective total synthesis of polyacetylene panaxjapyne C is described. The key reactions include regioselective opening of the epoxide and Cadiot-Chodkiewicz cross-coupling reactions. l-Ascorbic acid was used as a chiral pool material for the construction of the both terminal acetylenes.     

Enantioselective synthesis of 1-arylethanediols by rhodium-catalyzed transfer hydrogenation of α-tosyloxyarylketones

Abstract  Catalytic transfer hydrogenation of α-tosyloxyarylketones mediated by a chiral rhodium complex using an azeotropic mixture of formic acid/triethylamine afforded the corresponding 1-arylethanediol monotosylates in excellent yield with high enantioselectivity. Graphical abstract        

Cyclic chlorophosphites as scaffolds for the one-pot synthesis of α-aminophosphonates under solvent-free conditions

New α-aminophosphonates of the type (OCH₂CMe₂CH₂O)P(O)CH(NHCO₂R)(R′) [6a-i, 7a-e, and 8a-c] have been synthesized in high yields by a three-component reaction using (OCH₂CMe₂CH₂O)PCl (3), benzamide (or urethane or benzyl carbamate), and an aldehyde without using any catalyst under solvent-free conditions. This route can be readily adapted for bis-aminophosphonates as well as optically active binaphthoxy α-aminophosphonates; it also tolerates the phenolic -OH group as shown by the synthesis of hydroxy functionalized aminophosphonates. Partial hydrolysis of compounds 7a-d leads to products in which the phosphorinane ring is cleaved first. Compounds (OCH₂CMe₂CH₂O)P(O)CH[NHC(O)Ph](9-anthryl) (6f) and optically pure (R,S)-(−)-(C₂₀H₁₂O₂)P(O)CH(NHCO₂Et)(Ph) (14a) were characterized by X-ray crystallography.     

Stereoselective synthesis of belactosin C and its derivatives using a catalytic proline catalyzed crossed-aldol reaction

A highly practical and concise stereoselective total synthesis of belactosin C and synthetic variants was achieved using an S-proline catalyzed crossed-aldol reaction as the key step.     

Towards the biotechnological isomerization of branched sugars: d-tagatose-3-epimerase equilibrates both enantiomers of 4-C-methyl-ribulose with both enantiomers of 4-C-methyl-xylulose

Microbial oxidation of 2-C-methyl-d-ribitol and 2-C-methyl-d-arabinitol by Gluconobacter thailandicus NBRC 3254 produces 4-C-methyl-l-ribulose and 4-C-methyl-d-ribulose, respectively. Further, 4-C-methyl-l-ribulose and 4-C-methyl-d-ribulose were equilibrated by d-tagatose-3-epimerase (DTE) with 4-C-methyl-l-xylulose and 4-C-methyl-d-xylulose, respectively. These transformations demonstrate that polyol dehydrogenase and DTE act on branched synthetic sugars. The green preparation of all of the stereoisomers of 4-C-methyl pentuloses illustrates the ability of biotechnology to generate novel branched monosaccharides.     

Enantioselective synthesis of 1-arylethanediols by rhodium-catalyzed transfer hydrogenation of α-tosyloxyarylketones

Abstract  

Catalytic transfer hydrogenation of α-tosyloxyarylketones mediated by a chiral rhodium complex using an azeotropic mixture of formic acid/triethylamine afforded the corresponding 1-arylethanediol monotosylates in excellent yield with high enantioselectivity.     

First stereoselective total synthesis of (−)-stagonolide A

The first stereoselective total synthesis of the nonenolide (?)-stagonolide A is described. Olefin metathesis and epoxide opening reaction are the key steps involved.     

A flexible organocatalytic enantioselective synthesis of heptadeca-1-ene-4,6-diyne-3S,8R,9S,10S-tetrol and its congeners

A unified enantioselective route is developed for the synthesis of heptadeca-1-ene-4,6-diyne-3S,8R,9S,10S-tetrol and its synthetic congeners. A proline-catalyzed aminoxylation, cross-metathesis, Wittig reaction, and catalytic dihydroxylation are key steps of this synthesis. This new approach is envisioned to facilitate the synthesis of every representative member of the family with skeletal and stereochemical variation.