Synthesis of Functionalised Cyclohexanes from Carbohydrates
Beta-D-glucopyranose pentaacetate was photobrominated to give the 5-baromide from which 6-deoxy-Beta-D-xylo-hex-5-enopyranose tetraacetate was obtained by reductive elimination. This reaction sequence represents an efficient new route to the 5-ene. A detailed investigation into the photobromination of Beta-D-glucopyranose pentaacetate with bromine and with NBS led to the isolation of several by-products containing bromine substituents at C-1 and/or C-5; their reactions with zinc-acetic acid were studied, and the conformations. in solution of four alkenes derived from the 5-bromo compound were determined. 2,3,4-Triacylated 2,3,4,5-tetrahydroxycyclohexanones were Obtained by mercury (II) catalysed rearrangement of 5-deoxyhex-5-enopyranose esters. The mechanism of this rearrangement, and some enopyranose esters The mechanism of this rearrangement, reactions of the products were examined. The use of these new carbocyclic compounds in the synthesis of branched-chain cyclitol derivatives was explored. By means of diazomethane or, alternatively, hydrogen cyanide, substituted cyclohexanes with one-carbon branches and tertiary hydroxyl groups at the site of chain-branching were preared. Attempts to eliminate water from these tertiary alcohols to give substituted cyclohexene-carbonitriles or -carbaldehydes were unsuccessful.