Asymmetric aldol reactions using catalytic d(+)-proline: a new, economic and practical approach to a commonly employed C1–C6 keto-acid synthon of the epothilones
摘要:
A new approach to ketoacid 4, a common C1-C6 fragment used in the total synthesis of epothilones was initiated by direct aldol reaction of acetone with a pivaldehyde-like substance 5, catalyzed with D-proline, leading to a 2,6-diketoalcohol with better than 99% ee. Further intramolecular closure of the diketone 8 followed by oxidation of the silyl protected hydroxycyclohexenone 14 led to the desired product 4. None of the steps have been optimized, yet the overall yield for the four-step process is 31%. The use of commercially available D-proline to construct the chiral center of 4 under very mild reaction conditions provided an economical and practical method for its construction. (C) 2004 Elsevier Ltd. All rights reserved.
Asymmetric aldol reactions using catalytic d(+)-proline: a new, economic and practical approach to a commonly employed C1–C6 keto-acid synthon of the epothilones
摘要:
A new approach to ketoacid 4, a common C1-C6 fragment used in the total synthesis of epothilones was initiated by direct aldol reaction of acetone with a pivaldehyde-like substance 5, catalyzed with D-proline, leading to a 2,6-diketoalcohol with better than 99% ee. Further intramolecular closure of the diketone 8 followed by oxidation of the silyl protected hydroxycyclohexenone 14 led to the desired product 4. None of the steps have been optimized, yet the overall yield for the four-step process is 31%. The use of commercially available D-proline to construct the chiral center of 4 under very mild reaction conditions provided an economical and practical method for its construction. (C) 2004 Elsevier Ltd. All rights reserved.
Asymmetric aldol reactions using catalytic d(+)-proline: a new, economic and practical approach to a commonly employed C1–C6 keto-acid synthon of the epothilones
作者:Yansong Zheng、Mitchell A Avery
DOI:10.1016/j.tet.2003.12.048
日期:2004.2
A new approach to ketoacid 4, a common C1-C6 fragment used in the total synthesis of epothilones was initiated by direct aldol reaction of acetone with a pivaldehyde-like substance 5, catalyzed with D-proline, leading to a 2,6-diketoalcohol with better than 99% ee. Further intramolecular closure of the diketone 8 followed by oxidation of the silyl protected hydroxycyclohexenone 14 led to the desired product 4. None of the steps have been optimized, yet the overall yield for the four-step process is 31%. The use of commercially available D-proline to construct the chiral center of 4 under very mild reaction conditions provided an economical and practical method for its construction. (C) 2004 Elsevier Ltd. All rights reserved.