TOTAL SYNTHESES OF ENANTIOMERICALLY PURE D-GLYCOSYL AND L-GLYCOSYL DONORS AS COMPONENTS OF SANNAMYCIN-TYPE AMINOGLYCOSIDE ANTIBIOTICS

Both enantiomers of purpurosaminides C (ent-7b, 13a-c), of a 2-azido analogue (ent-16b) and of 2-azido epimers (ent-26b, ent-29b), suitably protected for their direct use as glycosyl donors, are prepared from racemic 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer, rac-1). The latter has been resolved on a preparative scale through the diastereoisomeric trifluoroacetylated 1'-amines obtained with (1R)- and (1S)-1 phenylethylamine, which allowed the combination of optical resolution with the introduction of the glycosyl 6-amino function.