Catalytic Asymmetric Synthesis of All Possible Stereoisomers of 2,3,4,6‐Tetradeoxy‐4‐Aminohexopyranosides

Abstract

We recently developed a divergent strategy for the synthesis of all eight possible 2,3,6trideoxyhexopyranosides with three stereogenic centers. However, the diastereoselectivity for one of the three stereogenic centers was low and it was not controlled by catalysts. In this update, we described a systematic method for the first catalytic asymmetric synthesis of all eight possible 2,3,6trideoxyhexopyranosides and all eight possible 2,3,4,6-tetradeoxy-4-aminohexopyranosides.The products derived from this strategy include the glycone of natural products grecocycline A, spinosyn A, and ossamycin. All three stereogenic centers in each product was controlled by a pair of chiral catalysts. The key to the success is the application of our recently developed dynamic kinetic stereodivergent acylation of Achmatowicz rearrangement products and chiral catalyst-directed reduction. Simple dimethylation of the 2,3,4,6-tetradeoxy-4amino sugars afforded derivatives of naturally occurring b-D-forosaminide and b-L-ossaminide.

Stereo- and Site-Selective Acylation in Carbohydrate Synthesis

“…Scheme 14 Selected bioactive natural products and saccharides made using a palladium-catalyzed glycosidation and divergent chiral catalystdirected tandem reduction While our previous divergent synthesis was useful, we published an update to this method in 2018. 19 Formation of the products shown in Scheme 12 originally proceeded through carbonate intermediates 68 and 69, and suffered from poor stereoselectivity (no greater than roughly 3:1) in the transformation from 13 (Scheme 15). We thought our previously published dynamic kinetic stereoselective acylation of lactols using chiral benzotetramisole catalysts 12 could be used instead to prepare 53-56 and their respective enantiomers.…”

Avanços Recentes Na Química Dos Aminoaçúcares: Ocorrência, Biossíntese, Síntese E Aplicação

“…Recentemente, Zhu et al 124 relataram a síntese assimétrica catalítica de oito possíveis 2,3,4,6-tetradesoxi-4-amino-hexopiranosídeos, dentre eles os compostos 129, 132, 135 e 138 (Esquema 27), e também a síntese das gliconas dos produtos naturais grecociclina A e B, espinosina A e ossamicina. Entretanto, segundo os autores, a diastereosseletividade para um dos três centros estereogênicos foi baixa e não controlada por catalisadores.…”

General Strategy for the Synthesis of Rare Sugars via Ru(II)-Catalyzed and Boron-Mediated Selective Epimerization of 1,2-trans-Diols to 1,2-cis-Diols

“…Although de novo synthesis can avoid the selectivity issue, only certain types of rare sugars can be prepared efficiently . The synthesis of rare sugars is still challenging, and strategies that can access a broad range of rare sugars are lacking, albeit a significant amount of effort is devoted to this area. , We have been interested in developing novel methods for the preparation of rare sugars and reported strategies for the de novo syntheses of a series of deoxy rare sugars recently . We envision that numerous rare sugars can be derived from common sugars if the stereochemistry of the secondary OH groups can be efficiently and selectively manipulated.…”