199870-96-7

Upstream product

• 10065-72-2 L-Alanine methyl ester 
• 157982-28-0 (1R)-S-ethyl [1-phenyl-1-tetrahydropyran-(2RS)-2-yloxy]-thioacetate 
• 157982-25-7 (1R)-tetrahydropyran-(2RS)-2-yl [(1R,3R)-1-(1,3-dithiane-1,3-dioxide-2-yl)-1-phenyl]methyl ether 
• 158060-53-8 (1R,3R)-1,3-dithiane-1,3-dioxide-2-[(1R)-1-phenyl]methanol 
• 100-52-7 benzaldehyde 

Downstream Products

• 79546-40-0 (2R)-methyl N-[(2-hydroxy-2-phenyl)acetyl]-L-alaninate 
• 79546-40-0 (S)-2-(2-Hydroxy-2-phenyl-acetylamino)-propionic acid methyl ester 

Relevant academic research and scientific papers

trans-1,3-dithiane-1,3-dioxide; a chiral acyl anion equivalent. Enantioselective synthesis of α-hydroxy- carboxylic acids, esters, amides and ketones

The reaction of (R,R)-(+)-1,3-dithiane-1,3-dioxide with aldehydes has been carried out and the dithiane dioxide moiety elaborated further. (R,R)-(+)-1,3-Dithiane-1,3-dioxide gave highly diastereoselective addition products with benzaldehyde and 3,4- dimethoxybenzaldehyde and single diastereomers were isolated in 84 and 76% purified yields respectively. Under similar conditions cyclohexane carboxaldehyde gave an easily separable mixture of diastereomers in 86% total isolated yield. The adducts were transformed into protected S- ethyl α-hydroxythioesters in 95-100% ee via a Pummerer reaction and subsequent trans-thioesterification protocol using LiSEt. Using LiSEt little racemisation occurred even with aryl substituted thioesters. Further transformations of thioesters to various α-hydroxy carboxylic acid derivatives (acids, esters, amides) without racemisation have been achieved. The approach resulted in the synthesis of the dimethyl ether of (R)-(-)-3,4-dihydroxymandelic acid in its naturally occurring form. Addition of dibutyl cuprate (derived from BuMgBr and Cu(I)Br) to the thioester gave the corresponding ketone in high yield and again without racemisation.

trans-1,3-Dithiane-1,3-Dioxide, a New Chiral Acyl Anion Equivalent for the Preparation of Masked Activated Acids: Application to the Synthesis of α-Hydroxy Acid Derivatives

trans-1,3-Dithiane-1,3-dioxide reacts with high diastereoselectivity with aromatic aldehydes and the 1,3-dithiane-1,3-dioxide moiety can be easily converted to a thiolester without racemisation by carrying out a Pummerer reaction; the thiolester is a group that can be readily transformed into acids, esters, amides, ketones and aldehydes.