Pp. Deshpande et Dc. Baker, A SIMPLE APPROACH TO THE SYNTHESIS OF THE CHIRAL SUBSTITUTED CHROMAN RING OF CALOPHYLLUM COUMARINS, Synthesis, (6), 1995, pp. 630-632
A stereoselective synthesis of the chiral 2,3-dimethylchroman-4-ol rin
g of the calophyllum coumarins is described. The chiral centers at C-3
and C-4 (chroman numbering) were introduced using (Z)-crotyldiisopino
campheylborane, and the chiral center at C-2 was introduced via mercur
y-assisted cyclization and demercuration, giving the required trans, t
rans-Me-Me-OH substituted chroman (benzo[b]pyran) ring.