ABSTRACT
The first syntheses of new antibiotics UPA0043 and UPA0044 were accomplished starting from commercially available 18beta-glycyrrhetinic acid and vanillin. The present syntheses involve the coupling of a sesquiterpenoid aldehyde and an aryllithium, the stereoselective formation of a p-quinone-methide system, and regioselective intramolecular cyclization via an epoxy ring opening. [reaction: see text]
Subject(s)
Antibiotics, Antineoplastic/chemistry , Antibiotics, Antineoplastic/chemical synthesis , Indolequinones , Indoles/chemistry , Quinones/chemistry , Quinones/chemical synthesis , Antibiotics, Antineoplastic/pharmacology , Molecular Structure , Quinones/pharmacologyABSTRACT
A new pentacyclic steroid, xestobergsterol C [1], possessing a cis C/D ring junction, has been isolated together with two known compounds, xestobergsterols A [2] and B [3], from the Okinawan marine sponge Ircinia sp., and the structure determined on the basis of spectral data. Reexamination of the nmr data of xestobergsterols A [2] and B [3] resulted in revision of the configuration at C-23 and of the conformation of ring D in 2 and 3. The absolute stereochemistry of xestobergsterol A [2] was established by the cd exciton chirality method.
