Total synthesis of (+)-(1,2,3/4,5)-2,3,4,5-tetrahydroxycyclohexane-1-methanol and (+)-(1,3/2,4,5)-5-amino-2,3,4-trihydroxycyclohexane-1 -methanol [(+)-validamine]. x-ray crystal structure of (3S)-(+)-2-exo-bromo-4,8-dioxatricyclo[4.2.1.0^3,7]nonan-5-one

The optical resolution of (±)-7-endo-oxabicyclo [2.2.1] hept-5-ene-2-carboxylic acid (±)-(1) has been accomplished by use of (R)-(+)- and (S)-(-)-α-methylbenzylamine, respectively. The absolute configuration of (-)-(1) has been determined on the basis of X-ray analysis of the bromo lactone (2) derived from it. The title branched-chain cyclitol (6), the antibiotic produced by Streptomyces sp. MA-4145, has been totally synthesized from (-)-(1), its absolute configuration being established. Synthesis of the penta-N,O-acetyl derivative (12) of (+) -validamine, the branched-chain aminocyclitol obtained by degradation of the antibiotic validamycin A, has also been carried out from (-)-(1).