The intramolecular nitrile oxide cycloaddition reaction on chiral (E) and (Z) olefins featuring a sulphuratom along the carbon chain connecting dipole and dipolarophile occurs with poor to excellent anti stereoselectivity, which is mainly affected by the substitutents at the allylic stereocenter. The possibility of converting the cycloadducts into stereoisomerically pure β-ketols has been established
Convenient Route to Both Enantiomers of a Highly Functionalized Trans-Disubstituted Cyclopentene. Synthesis of the Carbocyclic Core of the Nucleoside BCA
stereocontrolled synthesis of a diene with two syn-disposed substituents from a (R)-(+)-glyceraldehyde derivative, ring-closing metathesis of this diene, and functional group manipulation of the resulting trans-disubstituted cyclopentene. One of the enantiomers of the cyclopentenol thus obtained has been converted to an amino cyclopentene, the carbocyclic core of the nucleoside (−)-BCA, a potent inhibitor of HIV
highly convergent, stereoselective total synthesis of a ten-membered lactone, stagonolide G, is described. Epoxide ring-opening with vinyl Grignard, Yamaguchi esterification and ring-closing metathesis are the key steps involved in the present approach. d-Mannitol was used as a chiral pool material for the construction of both of the key fragments - the olefinic acid and the olefinic alcohol moieties. chiral
An enantiocontrolled entry to the tricyclic core of daphnicyclidin A with five chiral centers including an all-carbon quaternary center is reported. The synthesis features a highly diastereoselective conjugate addition of nitromethane, an Ireland-Claisen rearrangement, and a tandem acyliminium/Mannich-type reaction.