Synthetic Studies on the Validamycins. 5.^1,2 Synthesis of DL-Hydroxyvalidamine and dl-Valienamine

A first synthesis of the peracetyl racemate (25) of hydroxyvalidamine (3), one of the degradation products of antibiotic validamycin B (1), is reported. The present result fully confirmed the proposed structure of 3. The sequence of reactions involves stereospecific peracid oxidation of the protected branched-chain unsaturated cyclitol 18 to give rise to a versatile epoxide (19) and regioselective azidolysis of 19 followed by reduction of the azido group with hydrogen sulfide. In addition, the peracetyl racemate (30) of vahenamine (4) has been newly synthesized from the intermediate compound (26) of 3 by dehydration through the mesylate 27, a similar sequence of which may be generally applicable for preparation of other vahenamine derivatives.