Structural Elucidation of Garcipaucinones A and B From Garcinia paucinervis Using Quantum Chemical Calculations

Two tocotrienol derivatives, garcipaucinones A (1) and B (2), and a biosynthetically related known analogue (3) were isolated from the fruit of Garcinia paucinervis. Their structures including absolute configurations were unequivocally determined by spectroscopic methods complemented with electronic circular dichroism (ECD) calculations and gauge-independent atomic orbital (GIAO) NMR calculations. Compounds 1 and 2 are the first naturally occurring tocotrienol derivatives with a 3,10-dioxatricyclo-[7.3.1.0^2,7]tridecane skeleton incorporating an unusual γ-pyrone motif. A reasonable biosynthetic pathway for formation of the two compounds is proposed. The antiproliferative and anti-inflammatory activities of compounds 1 and 2 were also evaluated.