3‐Alkylated (R)‐2,3‐Dihydroxyalkyl p‐Toluenesulfonates – homochiral building blocks for modified steroid side chains

Abstract

Oxidative cleavage of 1,2:5,6‐di‐0‐cyclohexylidene‐D‐mannitol (2) with lead (IV) acetate yields (R)‐2,3‐0‐cyclohexylideneglyceraldehyde, which was transformed by oxidation and esterification into methyl 2,3‐0‐cyclohexylideneglycerate. Grignard reaction with various alkylmagnesium halides followed by acid‐catalyzed removal of the acetal group and reaction with p‐toluenesulfonyl chloride in pyridine furnished the title compounds (8a–d) in good chemical overall yield and high enantiomeric purity. The compounds were prepared as intermediates for the synthesis of a series of steroids with a modified side chain.

Synthesis of epothilones molecule fragment (15R)-C 13 -C 21 from D-mannitol

“…Here we report on the conversion of the latter into the C 13 -C 21 epothilone fragment (R)-(III), a promising intermediate for the epothilone synthesis through the stage of the hydroxy group substitution with the reversal of the streochemical confi guration of the atom C 15 [12] (Scheme 1). D-Mannitol was by the known procedure converted into biscyclohexylidene derivative VI [13], whose vicinal diol fragment was subjected to destructive oxidation by the method used with the corresponding isopropylidene analog [14] to obtain the known methyl 2,3-O-cyclohexylidene-D-glycerate (VII) (Scheme 2) that had been previously prepared from compound VI through its oxidation into the corresponding aldehyde [15]. The reaction of ester VII with ethylmagnesium bromide in the presence of an equimolar amount of titanium(IV) isopropoxide resulted in a good yield of cyclopropanol VIII, whereas the yield of the cyclopropanation product from the isopropylidene derivative of the D-methyl glycerate under similar conditions did not exceed 60% [11].…”