Highly Diastereoselective Cyclopentane Construction: Enantioselective Synthesis of the Dendrobatid Alkaloid 251F
摘要:
We report the first total synthesis, and thus structural confirmation, of the dendrobatid alkaloid 251F (1), based on the retrosynthetic analysis illustrated (1 <-- <-- 4). Key observations in this synthesis are that both the Rh-mediated cyclization of 1 and the anionic cyclization of 2 proceed with excellent diastereoselectivity.
Asymmetric syntheses of the enantiomerically pure trifunctional (R)-3-hydroxyesters (7)–(10) can be achieved by baker'syeastreduction of the hydrolysed β-keto carboxylates (2)–(5) instead of by reduction of the corresponding ester.
Highly enantioselective reduction of β-ketoesters with BINAP-Ru catalyst can be effected at 50 psig H2 and 80°, using a Parr shaker. A simplified preparation of the BINAP-Ru catalyst is reported.
使用Parr摇床,可以在50 psig H 2和80°下使用BINAP-Ru催化剂对β-酮酯进行高度对映选择性还原。报道了BINAP-Ru催化剂的简化制备。
Predicting the Diastereoselectivity of Rh-Mediated Intramolecular C−H Insertion
作者:Douglass F. Taber、Kamfia K. You、Arnold L. Rheingold
DOI:10.1021/ja9515213
日期:1996.1.1
Rhodium-mediated cyclization of the alpha-diazo ester 1 proceeds with high diastereoselectivity, to give the trisubstituted cyclopentane 5. A computational model (ZINDO and Molecular Mechanics) based on our current mechanistic understanding of the reaction is presented. This model correctly predicts the dominant diastereomer from the cyclization of 1 and the eight (Table 2) other alpha-diazo esters studied thus far.
Taber, Douglas F.; Silferberg, Lee J.; Robinson, Edward D., Journal of the American Chemical Society, 1991, vol. 113, # 17, p. 6639 - 6645
作者:Taber, Douglas F.、Silferberg, Lee J.、Robinson, Edward D.
DOI:——
日期:——
Studies toward the total synthesis of (+)-ptilomycalin A. Use of a tethered Biginelli condensation for the preparation of an advanced tricyclic intermediate
作者:Larry E. Overman、Michael H. Rabinowitz
DOI:10.1021/jo00064a007
日期:1993.6
An intramolecular ureidoaldehyde condensation, 16 + (R)-14 --> 19, is the key step in a seven-step preparation of the enantiopure spirotricycle 23, a potential intermediate for the enantioselective total synthesis of ptilomycalin A.