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).
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).
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