Homer-Wittig reactions of 4-O-benzyl-2,3:5,6-di-O-isopropylidene-D-mannose and 2,3,4,5,6,7-hexa-O-benzyl-6-D-glycero-2,3,4,5-D-galacto-heptose with methyl 2-benzyloxycarbonylamino-2-(diethoxyphosphoryl)acetate gave the corresponding alpha-dehydroamino acid derivatives in good yields, respectively. They were converted to methyl 3-deoxy-4,5:7,8-di-O-isopropylidene-alpha-D-manno-2-octulopyranosonate and methyl (methyl 3-deoxy-D-glycero-beta-D-galacto-2-nonulopyranosid)onate via methyl alpha-oxoalkanoate derivatives