Synthesis of Pseudo-β-Dl-galactopyranose and Pseudo-α-Dl-altropyranose

Abstract

Pseudo-β-Dl-galactopyranose and pseudo-α-Dl-altropyranose pentaacetates (10 and 11) were obtained in a seven step reaction starting from Dl-1,2-O-cyclohexylidene-5-deoxy-chiro-inositol (2).

Trimethylaluminium promoted rearrangements of unsaturated sugars into cyclohexanes

“…Compared to previous syntheses of related compounds [15][16][17] total stereoselection both at C-1 and C-5 was observed, as well as retention of the aglycon allowing transformations of a disaccharide such as 10. Furthermore, in comparison with the Al i Bu 3 -mediated rearrangement on disaccharides, this version leads to tertiary alcohols without de-O-benzylation side reaction.…”

A general norbornyl based synthetic approach to carbasugars and ‘confused’ carbasugars

“…OsO 4 -mediated dihydroxylation on 16 was stereospecific from the face opposite to the allylic hydroxyl group and furnished pseudo-a-DLaltropyranose carbasugar 17a and was fully characterized as its pentaacetate 17b. 7 In an alternate sequence, 16 was subjected to epoxidation with m-chloroperbenzoic acid in aqueous medium to furnish trans-epoxide 18 in a stereoselective manner. Interestingly, the epoxidation of 16 was dictated by steric considerations rather than by the usually encountered directing influence of the allylic hydroxyl group.…”

Chemical Synthesis of a Glycolipid Library by a Solid‐Phase Strategy Allows Elucidation of the Structural Specificity of Immunostimulation by Rhamnolipids

“…The stereochemical outcomes of the reactions were confirmed by correlation of the resulting carbasugar derivatives with the previously reported 5a‐carba‐β‐ D ‐glucopyranose 28a and 5a‐carba‐β‐ D ‐galactopyranose 28b , as outlined in Scheme : acid treatment (AcOH/THF/H 2 O) of the stannyl diacetonides 22a and 22b furnished destannylated tetraols that upon acetylation gave “carbasugar exo ‐glycals”32 27a and 27b , and subsequent ozonolysis followed by stereoselective reduction and acetylation yielded the previously described 5a‐carba‐β‐ D ‐glucopyranose pentaacetate { 28a ,33,34 [ α ] D 21 = +12.2 ( c = 1.0, CHCl 3 ) [ref 34b. +13.8 ( c = 1.0, CHCl 3 )]} and 5a‐carba‐β‐ D ‐galactopyranose pentaacetate { 28b ,35 [ α ] D 21 = –3.4 ( c = 0.4, CHCl 3 )}.…”