From l-Rhamnose to Rare 6-Deoxy-l-Hexoses

Abstract

Efficient and rapid transformation of cheaply available l-rhamnose into all the isomeric 6-deoxy-l-hexoses via regio- and stereoselective nucleophilic displacements of triflates is reported. The synthesis entails regioselective protections, one-pot double displacements of triflates, and cascade inversions. The methodology allows facile access to all the rare 6-deoxy-l-hexoses as stable thioglycoside building blocks.

Total Synthesis of the Tetrasaccharide Haptens of Vibrio vulnificus MO6-24 and BO62316 and Immunological Evaluation of Their Protein Conjugates

“…Several 2-azido-derivatives 4a – c and 6a – c of l -QuiNAc as glycosyl donors were synthesized according to Scheme 2 and used to probe the best methods and conditions for α-selective glycosylation. Dimethyltin dichloride (Me 2 SnCl 2 )-mediated regioselective benzoylation 20 of the C3-OH in β- l -thiorhamnoside 12 ( 21 ) afforded alcohol 13 (H-3 shifted to δ 5.17 ppm) in a 79% yield, which was then converted into the corresponding triflate using triflic anhydride (Tf 2 O) and pyridine. Substitution of the triflate with an azido group provided orthogonally protected 2-azido- l -QuiN 6a in a 62% yield over two steps.…”

Triacetonide of Glucoheptonic Acid in the Scalable Syntheses of d-Gulose, 6-Deoxy-d-gulose, l-Glucose, 6-Deoxy-l-glucose, and Related Sugars

“…Heptonic acid lactones with only acetonide protection derived from Kiliani synthesis on aldoses 18 or ketoses 19 are wellestablished intermediates for the efficient synthesis of highly functionalised targets. 20 This paper underlines the value of triacetonides 21 derived from seven carbon sugars; 2 is a divergent intermediate for access to rare sugars possessing either a D-gulo or L-gluco structural motif with any oxidation level at C1 or C6. This approach which may be general for heptonates increases chemical and biotechnological procedures for easy access to rare sugars.…”

Synthesis of L‐Hexoses: An Update

“…[5,77] Kulkarni lab also established the S N 2 displacement of triflates for rapidly accessing all the isomeric 6-deoxy L-hexoses from cheaply available L-rhamnose derived thioglycoside 76. [78] As shown in Scheme 13, the synthesis began with the conversion of 3-OBz β-rhamnothioglycoside 77 into its corresponding bistriflate and followed by displacement with TBANO 2 to make L-fucoside 78. To get L-quinovoside, first regioselective protection was carried out on 2,4-diol 77 under TBSCl, Imidazole condition to get 4-OTBS as the major product.…”