José L. Ravelo

New synthetic strategy for the construction of trans-fused medium-sized cyclic ethers: synthesis of the IJK framework of the polyether ciguatoxin

Abstract The synthesis of a conveniently functionalised oxocene-oxane-oxepane framework was achieved by two simultaneous one-carbon homologations followed by a one-pot double carbon-carbon bond-forming strategy.

Sesquiterpene lactones from Salvia palaefolia

Abstract The aerial part of Salvia palaefolia yielded (−)-glechomafuran, 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide and the new eudesmanolides: 1α-acetoxy-8α-hydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide and 1α,8α-dihydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide. The structure of the former new compound was determined from its spectral data and chemical behaviour and its absolute configuration by CD experiments. The absolute configuration of 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide was established by X-ray diffraction analysis.

Dactylomelol, a new class of diterpene from the sea hare aplysia dactylomela

Abstract A new bicyclic diterpene, dactylomelol, has been isolated from the shell-less mollusc Aplysia dactylomela and its structure was determined by the single crystal X-ray diffraction method together with assignments of 1 H- and 13 C-NMR data for dactylomelol.

Syntheses of marine molecules

The enantioselective total syntheses of (-)(E)ybisabolene-8,9-epoxide, (+) (2S,6R)-2-bromo-13-chamigrene, and (+)-chamigrene, important intermediates in the biosynthesis of natural sesquiterpenoids isolated from algae of the genus Laurencia, are described. The compounds are synthesized with regio nd stereocontrol by using simple forms of bridged intermediates. This represents a general strategy for the enantioselective construction of spirol5.5lundecane systems containing a chiral quaternary center. Our recent current progress towards the synthesis of the biologically active C25 tetronic acids isolated from sponges of the genus Ircinia is also described.

Approaches to the synthesis of the tetrahydropyran subunits of marine trans-fused polyether toxins

Abstract Cyclization/solvolysis of 2,3-epoxy cycloalk-5-en-1-ols proceed with complete regio- and stereoselectivity to yield cis-2,6-dialkyl-3,5-oxygenated tetrahydropyrans and thus assemble in two steps the key structural unit present in marine syn-trans-fused polyether toxins.

γ-Lactones α,β- and β,γ-fused to carbocycles as novel antiproliferative drugs

A set of gamma-lactones alpha,beta-fused and beta,gamma-fused to carbocycles have been synthesized and evaluated for their in vitro antiproliferative activities using the human cancer cell lines SW1573 (lung), T-47D (breast) and WiDr (colon). The compounds are obtained by intramolecular ring closing metathesis of the corresponding dienes. Active compounds exhibited GI(50) values in the range 8-18 microM. A structure-activity relationship is also discussed.

A new diterpene with a novel carbon skeleton from a marine alga

A new diterpene (1) possessing a novel carbon skeleton has been isolated from a brown alga Dictyota sp. and its structure determined by X-ray crystallography.

A new tricarbocyclic diterpene with a novel carbon skeleton from a marine alga

A new tricarbocyclic diterpene, chromophycadiol monoacetate (2), possessing a novel carbon skeleton, was isolated from a brown alga Dictyota sp. and its structure together with stereochemical features were determined by X-ray crystallography.