Synthetic Approaches to a Novel Carbohydrate Conjugated Diene: 4,6-O-Benzylidene-1,2,3-trideoxy-3-C-methylene-D-erytho-hex-1-enopyranose

Abstract

Four routes to the title compound 1 are outlined, three of which (i), (ii), and (iv) are simple one-step processes from readily available carbohydrate precursors. In the third route (iii) the α-keto benzoate 6a is methylenated and the benzoate group replaced by methanesulfonate. The product (6d) rearranges upon iodinolysis giving the primary allylic iodide (2b) which undergoes 1,4-elimination with methyl lithium to give the title compound (1). All reaction intermediates are readily crystallizable and with the exception of (6b) obtainable in > 80% yield.