Hydrolysis of benzofuran derivative (10) with concomitant aromatisatio
n produced the biaryl system (11). Subsequent Sharpless asymmetric epo
xidation of the cinnamyl alcohol (13) gave atropisomers (14) and (15)
conveniently separated by chromatography. Independent derivatisation o
f naphthylisoquinoline ring with 14 and 15 furnished korupensamine ana
logues (18) and (19). Comparison of CD spectra with those of natural p
roducts assigned the stereostructures of 18 and 19.