2-AMINO-2-DEOXYHEXOSES AS CHIRAL EDUCTS FOR HYDROXYLATED INDOLIZIDINES - SYNTHESIS OF (+)-CASTANOSPERMINE AND (+)-6-EPICASTANOSPERMINE

D-2-Amino-2-deoxyglucosaminic acid, obtained from D-glucosamine, and a D-2-amino-2-deoxymannosaminic acid derivative, obtained from D-glucono-delta-lactone, were derivatized and converted to the corresponding configurationally stable aldehydes. The N-(9-phenylfuoren-9-yl)-protected mannosamine derivative was readily transformed into a variety of configurationally stable alpha-amino ketones, thus providing convenient and versatile chiral educts. These educts may be envisaged as derivable from polyhydroxy alpha-amino acids. Examples of the utility of these chiral educts are provided by the efficient conversion of a D-mannosaminic acid derivative into the polyhydroxy indolizidine alkaloids (+)-castanospermine and (+)-6-epicastanospermine.