Stereocontrolled Syntheses of C-Aryl Taxanes By Intramolecular Heck Olefination. Novel Instances of Diastereofacial Guidance By Proximal Coordination
摘要:
Stereospecific syntheses of baccatin III constructs bearing an aromatic C-ring (2a and 2b) have been demonstrated. A key step involves the use of an intramolecular Heck olefination reaction to form the C-10-C-11 bond (see transformations 15 --> 16 and 27 --> 28). Novel stereospecific reactions en route to 2a and 2b were also discovered (see 8 --> 10, 8 --> 23, 13 --> 14, and 25 --> 26).
A concise synthesis of a highly functionalized C-aryl taxol analog by an intramolecular Heck olefination reaction
摘要:
A palladium(0) catalyzed intramolecular Heck olefination used to establish the C-10-C-11 connection in a highly functionalized taxane analog is described.
Synthesis of a diterpene taxoid skeleton, bicyclo[9.3.1]pentadecatriene
作者:Satoshi Shibuya、Minoru Isobe
DOI:10.1016/s0040-4020(98)00334-2
日期:1998.6
1]pentadecatriene skeleton was investigated by employing cyclization reactions using two key precursors bearing acetylene cobalt complex. Cyclization for the synthesis of strained twelve-membered ring was achieved via Nicholas type reaction in reasonable yield. Reductive decomplexation of the dicobalthexacarbonyl moiety of the cyclization product was achieved with n-Bu3SnH in the presence of a catalytic amount
Silicon-tethered intramolecular nucleophilic additions of a hydroxymethyl unit to ketones in β-hydroxyketones have been developed. The product obtained by this protocol was successfully converted to chiral A-ring moieties of Taxol™. Also developed was a promising silicon-tethered intramolecular α-alkylation reaction of the cyclic hydroxyketone.
preparations of the taxolA-ringfragment are described: one via organocatalyzed α-aminoxylation and the other via Sharpless asymmetric dihydroxylation (SAD). The former approach affords the A-ringfragment in 10 steps, and the latter approach involves eight steps to afford the new A-ringfragment in 91% ee, which is made enantiomerically pure through recrystallization. The new A-ringfragment bearing a bromoalkene