Collect. Czech. Chem. Commun. 1985, 50, 1994-1999

Isopropylidenation of L-arabinose N,N-dimethylhydrazone

Miroslav Koóš and Harry S. Mosher

Department of Chemistry, Stanford University, Stanford, California 94305, U.S.A.


Direct isopropylidenation of L-arabinose N,N-dimethylhydrazone (I) was studied. Four major products whose structures were proven were produced in varying ratios depending upon the conditions. 2,2-Dimethoxypropane and sulfuric acid at 20 °C gave a 36% yield of 2,3:4,5-di-O-isopropylidene-L-arabinose N,N-dimethylhydrazone (II). Attempted aldol condensations directly on this hydrazone with paraformaldehyde were unsuccessful. This hydrazone was readily hydrolyzed to the corresponding protected aldehyde VI which underwent an aldol-Cannizzaro reaction to give the branched chain pentitol VII in high yield.