Claude Spino

Anti-HIV coumarins from Calophyllum seed oil

The seeds of Calophyllum cerasiferum Vesque (Family-Clusiaceae), and Calophyllum inophyllum Linn. (Family-Clusiaceae) contain several known coumarins, among which were the potent HIV reverse transcriptase inhibitors costatolide and inophyllum P. Calophyllum cerasiferum contained (-)-calanolide B as its major coumarin constituent in significant amount and thus constitute a renewable source of this compound.

Sterically biased 3,3-sigmatropic rearrangement of chiral allylic azides: application to the total syntheses of alkaloids.

We describe a tandem Mitsunobu/3,3-sigmatropic rearrangement of allylic azides on a chiral auxiliary system that favors one regioisomer thanks to its exceptional steric bias. The sequence may be completed by the oxidative cleavage of the auxiliary or by a ring-closing metathesis reaction that produces a carbo- or heterocycle directly and a recyclable form of the chiral auxiliary. Applications of the methodology to the total synthesis of (+)-coniine, (+)-lentiginosin, and (+)-pumiliotoxin C are reported.

Enantioselective synthesis of (+)- and (−)-dihydrokawain

Abstract The first asymmetric synthesis of (+)- and (−)-Dihydrokawain, an α-dihydropyrone isolated from the roots of Piper mythisticum , is reported. (+)-Dihydrokawain is the natural product and is of S -configuration.

Stereoselective Synthesis of (+)-Aspidofractinine

We describe the synthesis of (+)-aspidofractinine, the enantiomer of a naturally occurring alkaloid of the kopsane family. Key features of the synthesis include a stereospecific cyanate to isocyanate rearrangement on a chiral scaffold, a ring-closing alkene metathesis to cleave the chiral auxiliary, and a chemoselective cyclopropanation to introduce the quaternary carbon at position 7 of aspidofractinine.

A New Look at the Diels–Alder Transition State

The chronology of π-orbital mixing in the Diels-Alder cycloaddition of butadiene and ethylene differs for the two main interactions, the HOMOdiene -LUMOdieneophile and HOMOdienophile -LUMOdiene interactions. The C2-C3 π bond of the cycloadduct is already well developed at the level of the transition state, which is reminiscent of a late transition state.

Photochemical Rearrangement of N-Chlorolactams: A Route to N-Heterocycles through Concerted Ring Contraction

We report a novel ring contraction allowing the direct conversion of N-chlorolactams to their corresponding ring-contraction N-heterocycles upon photolysis. Results show that the rearrangement occurs with a variety of N-chlorolactams and that the greater the substitution at the migrating carbon, the greater the yield of product. Importantly, stereochemistry at the migrating carbon is conserved in the product. Rearranged products were isolated as their methyl carbamates in yields varying from 17% to 58%, with the major side product being the recyclable parent lactam.

Stereoselective synthesis of (+)-euphococcinine and (-)-adaline.

We describe the syntheses of (+)-euphococcinine and (-)-adaline, two naturally occurring alkaloids containing a quaternary carbon bearing a nitrogen atom. Key features of the syntheses are a 3,3-sigmatropic rearrangement to give an all-carbon quaternary center, a ring-closing alkene metathesis to give an 8-membered ring, and the use of a single enantiomer of p-menthane-3-carboxaldehyde to make two natural alkaloids of opposite configuration.

Efficient syntheses of optically active 2-arylalkanoic acids

Abstract A highly enantioselective synthesis of 2-arylpropanoic acid was achieved, using a new developed methodology of cuprate addition to chiral carbonates derived from menthone.

Formal intramolecular (4 + 1)-cycloaddition of dialkoxycarbenes: control of the stereoselectivity and a mechanistic portrait.

The stereoselective synthesis of 5-5, 6-5, and 7-5 fused O-heterocyclic compounds is reported. The key reaction is a formal intramolecular (4 + 1)-cycloaddition involving a dialkoxycarbene and an electron-deficient diene where the stereoselectivity is dependent on the length of the tether. An analysis of the stereochemical outcome of this reaction sheds light on its complex mechanistic picture. High-level calculations were used to support the proposed mechanistic portrait.

Benzophenones of Garcinia pseudoguttifera (Clusiaceae)

Four biogenetically related benzophenones have been isolated from the Fijian Garcinia pseudoguttifera. They are: 6-hydroxy-2,4-dimethoxy-3,5-bis(3-methyl-2-butenyl)benzophenone (myrtiaphenone-A); 2,2-dimethyl-8-benzoyl-7-hydroxy-5-methoxy-6-(3-methyl-2-butenyl)benzopy ran (myrtiaphenone-B); 2,6-dihydroxy-4-methoxy-3,5-bis(3-methyl-2-butenyl)benzophenone (vismiaphenone-C) and a new benzophenone, 2,2-dimethyl-8-benzoyl-3,7-dihydroxy-5-methoxy- 6-(3-methyl-2-butenyl)-3,4-dihydrobenzopyran (pseudoguttiaphenone-A). Pseudoguttiaphenone-A could be biogenetically derived from vismiaphenone-C. The major component of G. pseudoguttifera was identified as eupha-8,24-dien-3 beta-ol.