Aldol enantiospecific

A novel route to 2-deoxY-2-C-alkvl-erYthro-pentoses has been devised by way of aldol reaction of ketene acetals such as 1-tert-butyldimethylsilyloxy-l-methoxyprop-l-ene with 2,3-Q-isopropylidene-D-glyceraldehyde. The absolute configuration of the lactone (48), isolated from Marshallia tenuifolia. has been confirmed by its enantiospecific synthesis. The aem-dinethylated oxime (49) has been specifically functionalised by a cyclopalladation - oxidation sequence giving, by way of the characterised organopalladium intermediate (50), the acetate (51). A study of the conformations of 3-deoxy-3-C-methyl- and... 

An enantiospecific route to the synthesis of tetrasubstituted 6-lactones has been developed by Staunton et al. by lactonization of 6-hydroxy acids [54] (Scheme 17). The Evans aldolization of oxazoUduume 85 with optically active aldehyde 86 gave the Evans aldol product 87. An oxidative removal of the chiral auxiliary followed by hydroxyl deprotection and cyclization furnished the tetrasubstituted 6-lactone 90... 

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