A highly stereoselective intramolecular aldol condensation. Part I. Nuclear magnetic resonance spectroscopic investigation of the stereochemistry of the products derived from the reaction of 2,2′-O-methylene-bis-D-glycerose with base

Abstract

The intramolecular aldol condensation of 2,2′-O-methylene-bis-D-glycerose has been found to yield only two of the four possible diastereomeric products. At higher base concentration or prolonged reaction times, these products undergo a Cannizzaro reaction. The stereochemistry of the products derived from the aldol condensation has been established by means of labelling experiments and by examination of the products by 1Hmr and 13Cmr spectroscopy. The major and minor products of the reaction have been identified as being 2-C-hydroxymethyl-2,4-O-methylene-D,L-ribose (7) and 2-C-hydroxymethyl-2,4-O-methylene-D,L-xylose (8), respectively. The preferential stabilization of these products in the reaction by means of intramolecular hemiacetal formation is proposed as a driving force for the high degree of stereoselectivity; this possibility is supported by the isolation of the bicyclic systems expected from such a reaction. Conditions have been chosen such that 7 is formed exclusively.

Evidence of benzilic rearrangement during the electrochemical oxidation of d-glucose to d-glucaric acid

“…It was not until 1934 that Schmidt et al described the correct structure, 9 which was later extensively studied, after it became available from tannin of witch hazel (Hamamelis virginiana L.). [16][17][18][19] To this day, very few syntheses of D-hamamelose have been described and most of them involved low yielding multistep syntheses. 20-22 2-(L-threo-1,2,3-Trihydroxypropyl) tartronic acid, on the other hand, was prepared from the reaction of dehydroascorbic acid under alkaline conditions; however, no large scale analytical sample could be obtained for further experimentation.…”

A highly stereoselective intramolecular aldol condensation. Part II. Synthesis of D,L-hamamelose from 2,2′-O-methylene-bis-D-glycerose

“…Since the thioglycosides can be readily converted into the free sugar, the mercaptolysis of the products of the aldol condensation was investigated as a means of converting 2,2'-0-methylene-bis-D-glycerose (1) into D,L-hamamelose. Can Results and discussion Treatment of the aldol-condensation product mixture (1) with ethanethiol and hydrochloric acid for 2 h, followed by acetylation of the resulting mixture, afforded, after recrystallization, white needles which were identified as being…”