Synthesis of Polyhydroxylated Pyrrolizidine Alkaloids of the Alexine Family by Tandem Ring-Closing Metathesis−Transannular Cyclization. (+)-Australine
作者:James D. White、Peter Hrnciar
DOI:10.1021/jo0012748
日期:2000.12.1
9 via oxazolidinones 15 and 51, respectively, underwent ring-closingmetathesis with Grubbs's catalyst to give azacyclooctenes 26 and 55. Treatment of each azacyclooctene with m-chloroperoxybenzoic acid afforded beta-epoxide 28 from 26 and alpha-epoxide 61 from 60. Basic hydrolysis of each of these oxazolidinones was accompanied by transannular attack at the epoxide by nitrogen, resulting in 2-(O-b
skeleton was assembled by means of Julia-Kocienski (C16-C17) and Horner-Wadsworth-Emmons (C21-C22) olefinations. Still-Gennari olefination was used for the C2-C3 ring closure. The key step of the synthesis was a regioselective C16-C17 matched Sharpless asymmetric epoxidation.
Total Synthesis of Halicholactone and Neohalicholactone<sup>1</sup>
作者:Douglas J. Critcher、Stephen Connolly、Martin Wills
DOI:10.1021/jo962312j
日期:1997.9.1
The total synthesis of the marine natural products neohalicholactone (1) and halicholactone (2), in enantiomerically pure form, are reported. Key steps in the synthesis of each compound include a cis-selective Wittig reaction, stereoselective cyclopropanation, nine-membered lactone formation using the Yamaguchi method and late-stage stereoselective Cr(II)/Ni(II) mediated coupling of vinyl iodides 39 and 50 with aldehyde 14. In the case of the neohalicholactone synthesis the two major components which were coupled in this convergent synthesis were each derived from the enantiomers of commercially available malic acid. The synthesis served to confirm the original assignment of absolute configuration which was made by Yamada and Clardy. We also demonstrated, through the preparation of diastereoisomers, that another reported compound closely related to neohalicholactone is likely to be the C-15 epimer 67.
Epothilone B and its Derivatives as Novel Antitumor Drugs: Total and Partial Synthesis and Biological Evaluation
作者:Johann Mulzer
DOI:10.1007/s007060070099
日期:2000.3.16
Microtubule stabilizing natural products, as exemplified by paclitaxel (taxol(R)), are being considered as novel drugs against malignant therapy resistent solid tumors. Among these compounds, epothilone B and some of its derivatives have emerged as particularly promising candidates for industrial development. The total and partial syntheses of these compounds are described in detail, and some of the most important recent results on their biological activity are discussed.
described, starting from optically pure (S)-malic acid and methyl (R)-3-hydroxy-2-methylpropionate. The synthesis is highly convergent by coupling the three fragments C1-C6 (fragment D), C7-C10 (fragment C), and C11-C21 (fragment B). Key steps are two stereoselectiveWittig type olefinations to generate the 12,13- and 16,17-double bonds, an enantioselective Mukaiyama aldol addition to synthesize fragment