RUO4-CATALYZED OXIDATIVE POLYCYCLIZATION OF SQUALENE. DETERMINATION OF THE CONFIGURATION OF THE PENTA-TETRAHYDROFURANYL DIOL PRODUCT

The configuration of the penta-tetrahydrofuranyl diol (penta-THF) product obtained by the single-step, RuO4-catalyzed oxidative polycyclisation of squalene has been determined as cis-threocis- threo-trans-threo-trans-threo-trans. The cis-cis-trans-trans-trans sequence for the five contiguous THF rings has been established through extensive 2D-NMR studies carried out both on the intact molecule and on some of its derivatives, including the oxidative cleavage products obtained by degradation of the penta-THF with PCC/AcOH. Four different chemical approaches were devised to determine each of the four threo relationships within each carbon pair connecting adjacent TFH rings in the molecule. To this aim, use has been made of the mono-, bis- and tris-THF diol intermediates of the oxidative process, obtained from the partial oxidation of squalene, as well as, inter alia, of a mono-THF bis-lactone product obtained from the penta-THF through a bidirectional double PCC degradation.