Abstract
The lichen metabolite (+)-bourgeanic acid (1) was synthesized in 12 steps and 3.4% overall yield from (R)-2-methyl-1-iodobutane (53) by a sequence which confirmed that this aliphatic depside is the self-este- rification product of (2R,3S,4R,6R)-2,4,6-trimethyl-3-hydroxyoctanoic acid. Alkylation of the enolate of (S)-N-propionylprolinol (48) with (53) gave the amide (60) which was transformed to (2R,4R)-2,4-dimethyl- hexanal (4). The latter was reacted with the crotylboronate (68), pre- pared from (S,S)-(-)-diisopropyl tartrate, to afford (3R,4S,5R,7R)-3,5, 7-trimethyl-1-nonen-4-ol (65) as the major diastereomer. Protection followed by ozonolysis and oxidation furnished (-)-hemibourgeanic acid (2). The β-lactone (73) derived from (2) was used to acylate (65), and the resulting ester (74) was subjected to oxidative ozonolysis to yield (+)-1
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call