Biologically Potent L‐Hexoses and 6‐Deoxy‐L‐hexoses: Syntheses and Applications

Abstract

For Abstract see ChemInform Abstract in Full Text.

Synthesis of l-Hexoses

“…The highly constrained exocyclic alkene 593 (for preparation, see Scheme ) has been stereoselectively reduced using palladium on carbon to give 6-deoxy- l -idofuranoside 594 (Scheme ). ,,, This pyranoside was liberated by acidic treatment followed by peracetylation to give 6-deoxy- l -idopyranoside 595 . Epimerization of C3 was accomplished by oxidation and stereoselective reduction of compound 597 derived from 596 by removal of the 3,5-isopropylidene and regioselective silylation to give 598 .…”

“…Therefore, syntheses of l -sugars from common carbohydrates have gained much attention throughout the history of carbohydrate chemistry. Several different approaches to synthesis of l -sugars from d -sugars have been suggested, of which the most prominent and interesting routes will be discussed. − Tedious protecting group manipulations and thereby lengthy routes are often unavoidable using this approach. However, in some cases, the early installation of orthogonal protecting groups can be a great advantage for glycosylations and hence in the long term save time and material.…”

Synthesis of Four Orthogonally Protected Rare l-Hexose Thioglycosides from d-Mannose by C-5 and C-4 Epimerization

“…Therefore, it is important to produce l -sugars from common carbohydrates by cost-effective and high-yielding synthetic routes. To meet the demand of l -sugars, various strategies have been developed for their synthesis [ 20 , 21 , 22 , 23 , 24 ], including C-5 epimerization of readily available d -sugars [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], homologation of carbohydrates with shorter chains [ 38 , 39 , 40 , 41 , 42 ], de novo synthetic routes [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ], head to tail inversion [ 51 , 52 , 53 , 54 , 55 , 56 ], site selective epimerization [ 57 , 58 ], C-H activation [ 59 , 60 ], and enzymatic synthesis [ 61 , 62 ]. However, there are very few approaches that provide the l -sugars as glycosyl donors, e.g., in form of thioglycosides, ready for glycosylation [ 60 , 63 , 64 , 65 , …”