Coupling of anhydro-aldose tosylhydrazones with hydroxy compounds and carboxylic acids: a new route for the synthesis of C-β-d-glycopyranosylmethyl ethers and esters

Abstract

Cross couplings of O-peracylated 2,6-anhydro-aldose tosylhydrazones (C-(b-D-glycopyranosyl) formaldehyde tosylhydrazones) with alcohols, phenols, and carboxylic acids were studied under thermic or photolytic conditions in the presence of K 3 PO 4 or LiOtBu. The reactions failed with EtOH, BnOH, or tBuOH, however, (CF 3) 2 CHOH, electron poor phenols and carboxylic acids gave the corresponding C-b-D-glycopyranosylmethyl ethers and esters, respectively, representing a new access to these glycomimetic compounds.

Pd-catalyzed coupling reactions of anhydro-aldose tosylhydrazones with aryl bromides to produce substituted exo -glycals

“…As a part of a program targeting the systematic study of applications of anhydro-aldose tosylhydrazones (compounds H in Scheme 1) as coupling partners in metal-free [4,5] and transition metal-catalyzed coupling reactions we have been interested in the Pd-catalyzed coupling of H with bromobenzenes. According to general mechanistic considerations, such coupling reactions [6][7][8] are expected to result in substituted exo-glycals (compounds E in Scheme 1).…”

Synthesis and photoinitiated thiol–ene reactions of exo-mannals – a new route to C-β-d-mannosyl derivatives

“…Their NMR study clearly showed the 4 C 1 conformation of the ring and the a(D) anomeric conguration which can be explained by the anchimeric effect of the 2-O-acyl substituent and also corresponds to the anomeric effect of the CN substituent forcing this group to occupy an axial position. [38][39][40] Subsequently cyanides 2 were transformed into the tosylhydrazones 3 under reductive conditions in the presence of tosylhydrazine, which on deprotonation by K 3 PO 4 41 (instead of the less easily handled NaH 34 ) and heating to reux temperature gave exo-mannals 4. The pyranoid ring of tosylhydrazones 3 and exo-mannals 4 had a 5 C 2 conformation according to the 3 J coupling constants between H-2, H-3, H-4, H-5 and H-6 ( Table 1).…”

New syntheses towards C-glycosyl type glycomimetics

“…With phenols 80 were formed in moderate yields (Entry 3). In the reactions with carboxylic acids the yields of 80 increased to give the best results with sugar derived acids (Entries 4-6) [105]. The glycosylmethyl sulfides 76 were obtained in moderate and good yields with aliphatic thiols and thiophenols, respectively (Entries 7 and 8) [106].…”