Self-induced diastereoselective oxidation of vinyl sulfoxides bearing a chiral hydroxy group as a way of preparation of optically active sulfinyl dienophiles and their use in the asymmetric Diels-Alder reactions to cyclopentadiene
Synthesis of cyclopentadiene derivatives by retro-Diels–Alder reaction of norbornadiene derivatives
作者:Erdin Dalkılıç、Arif Daştan
DOI:10.1016/j.tet.2015.02.023
日期:2015.4
Synthesis of cyclopentadiene derivatives starting from norbornadiene was investigated using dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate. The products obtained were either cyclopentadienes or diazines depending on the substituents. The driving force for the formation of these products was discussed in terms of electronic effects.
Preparation of Alkyl-Substituted Indoles in the Benzene Portion. Part 11. Total Synthesis of (6R,8S)-Herbindole A, (6R,8S)-Herbindole B, (6R,8S)-Herbindole C, (6R,8S)-cis-Trikentrin A, (6R,8S)-cis-Trikentrin B, (6R,8R)-trans-Trikentrin B, and (6R,8R)-iso-trans-Trikentrin B. Determination of the Absolute Structures of Natural Herbindoles and Trikentrins.
The key intermediate, (3R, 5S)-3, 5-dimethyl-1-cyclopentenylmethanol (13) for chiral syntheses of herbindoles and trikentrins, was prepared from the known Dields-Alder adduct 12. Employing pertinent methodologies developed in the previous model study (preceding paper), the title herbindoles 31, 34, and 38 as well as trikentrins 4, 6, 41, and 47 having (6R, 8S)- or (6R, 8R)-absolute configuration of the dimethyl groups on the 1, 6, 7, 8-tetrahydrocyclopent[g]indole moiety were synthesized starting from 13 by way of precursor compounds 24b, 27a, and 27b for the crucial indole cyclization reaction. The following results were also obtained. (i) The proposed chemical structures of three herbindoles were confirmed. (ii) The absolute structures of herbindole A and trans-trikentrin B were established to be 1 and 7 by directly comparing optical properties between synthetic materials and the natural products. (iii) The absolute structures of herbindole B (2) and herbindole C (3) were assumed by analogy with 1. (iv) The absolute structures of cis-trikentrin B (6) and iso-trans-trikentrin B (8) were estimated by a circular dichroism (CD) analysis study. (v) Our previous proposal for the absolute configuration of cis-trikentrin A (4) was further confirmed.
Chiral epoxides as recoverable auxiliaries in the synthesis of optically active sulpinyl dienophiles
作者:Ottorino De Lucchi、Maurizio Buso、Giorgio Modena
DOI:10.1016/s0040-4039(00)95662-4
日期:1987.1
The Diels-Alder addition of the sulfinyl dienophiles derivedfromchiral styrene oxide proceeds highlydiastereoselectively to produce adducts which can be transformed into enantiomeric compounds with recovery of the chiralauxiliary. A general assignment of the stereochemistry of the Diels-Alder cycloaddition of vinyl sulfoxides is proposed.
glycosides were applied to the reaction smoothly, and N-alkyl (primary, secondary and tertiary) C4-glycosidic indoles can also be obtained by this method. In terms of mechanism, the key ANP intermediates characterized by X-ray single-crystal diffraction and further controlled experiments proved that the migration-insertion of smNBDs with phenylpalladium intermediate endows them with high chemo- and