BACCHARANE (18,19-SECOLUPANE) - A RARE TRITERPENOID SKELETON WIDESPREAD IN TRIASSIC SEDIMENTS AND PETROLEUM FROM THE ADRIATIC BASIN

Baccharane (18,19-secolupane) 1, a triterpenoid skeleton seldom encountered in living organisms, has been characterized together with 17betaH-des-E-lupane 2, one of its minor degradation products, in Italian Triassic sediment and crude oil samples from the Adriatic Basin by synthesis of standards. Reports of baccharane-derived triterpenoids in the field of natural products are scant and up to now restricted to terrestrial plants (angiosperms and ferns). In this regard, sedimentary baccharane derivatives may indicate a continental contribution (ferns?) to fossil organic matter; but they may also represent a contribution of as yet undetermined marine microorganisms, as has been proposed for dammarenes and dammaranes. Alternatively, they could be the bio/geochemical transformation products of biosynthetically closely related precursors such as lupane- or dammarane-type triterpenoids. The apparently restricted occurrence of baccharane derivatives in geological samples (up to now detected only in Triassic sediments of the Adriatic Basin) confers upon these compounds great value as correlation parameters and possibly as source indicators.