H. Konno et al., SYNTHETIC STUDIES ON ANNONACEOUS ACETOGENINS .3. SYNTHESIS OF 2 POSSIBLE DIASTEREOISOMERS OF THE EPOXY LACTONE PROPOSED FOR EPOXYROLLIN-A, Bioscience, biotechnology, and biochemistry, 59(12), 1995, pp. 2355-2357
Syntheses of two possible stereoisomeric epoxy lactones (20S,21R)- and
(20R,21S)-1 that have been proposed for epoxyrollin A, a structural r
epresentative of biosynthetic precursors of tetrahydrofuran annonaceou
s acetogenins, are described. Protected dihydroxy compound 4, which is
the latent epoxy moiety of (20S,21R)- and (20R,21S)-1, was prepared b
y an 8-step sequence via Sharpless asymmetric dihydroxylation, startin
g from allyl alcohol 6. Preparation of gamma-lactone moiety 5 was cond
ucted by the method reported earlier, A palladium-catalyzed cross coup
ling reaction of 4 with 5 gave enyne 3, which, by a 3-step sequence, w
as converted into (20S,21R)- and (20R,21S)-1. The C-13-NMR and mass sp
ectral data of the two synthetic diastereoisomers are not in accordanc
e with those recorded for epoxyrollin A. Consequently, the structure o
f epoxyrollin A needs to be revised.