Hydroboration-Oxidation of (±)-(1α,3α,3aβ,6aβ)-1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products.

Hydroboration-oxidation of 2α,4α-dimethanol-1β,5β-bicyclo[3.3.0]oct-6-en dibenzoate () gave alcohols (symmetric) and (unsymmetric) in ~60% yield, together with the monobenzoate diol (37%), resulting from the reduction of the closer benzoate by the intermediate alkylborane. The corresponding alkene and dialdehyde gave only the triols and in ~1:1 ratio. By increasing the reaction time and the temperature, the isomerization of alkylboranes favours the un-symmetrical triol . The PDC oxidation of the alcohols gave cleanly the corresponding ketones and and the deprotection of the benzoate groups gave the symmetrical ketone , and the cyclic hemiketal , all in high yields. The ethylene ketals of the symmetrical ketones and were also obtained. The compounds , , , , could be used for synthesis of new (iso)carbacyclin analogues. The structure of the compounds was established by NMR spectroscopy and confirmed by X-ray crystallography.