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.O]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).