Application of the Ibuka-Yamamoto reaction to a problem in stereochemical communication: a strategy for the stereospecific synthesis and stabilization of the triene substructure of rapamycin through sulfone substitution
摘要:
The aldehydes 49 and 55 corresponding to carbons 13-30 in a projected total synthesis of rapamycin have been synthesized. The LACDAC technology was used to elaborate dithiane enal 5. The aldehyde 4 was synthesized from D-(+)-glucose. A critical element of that construction involved cuprate-induced displacement reactions on enoates 7 and 8 (see formation of esters 9a and 9b) to correlate the stereochemistry of carbons 8 and 12. The feasibility of conducting a Nozaki-Kishi reaction between iodosulfone 6 and aldehyde 4 was a major simplification. Julia coupling between sulfone 5 and aldehyde 43 was followed by acetylation and elimination of acetic acid. The triene sulfone 54 was obtained stereospecifically. The C4 sulfone linkage is a considerable stabilizing element on the C1-C6 triene. Its presence allows for removal of the dithiane linkage (see formation of aldehyde 55). Cleavage of the sulfone is accomplished with sodium analgam without reduction of an aldehyde function at C30 (see formation of 49).
Total Synthesis and Structural Elucidation of Azaspiracid-1. Construction of Key Building Blocks for Originally Proposed Structure
作者:K. C. Nicolaou、Petri M. Pihko、Federico Bernal、Michael O. Frederick、Wenyuan Qian、Noriaki Uesaka、Nicole Diedrichs、Jürgen Hinrichs、Theocharis V. Koftis、Eriketi Loizidou、Goran Petrovic、Manuela Rodriquez、David Sarlah、Ning Zou
DOI:10.1021/ja0547477
日期:2006.2.1
required for the totalsynthesis of the proposedstructure of azaspiracid-1 (1a) are described. Key steps include a TMSOTf-induced ring-closing cascade to form the ABC rings of tetracycle 65, a neodymium-catalyzed internal aminal formation for the construction of intermediate 98, and a Nozaki-Hiyama-Kishi coupling to assemble the required carbon chain of fragment 100. The synthesized fragments, obtained stereoselectively
A Unified Total Synthesis of the Immunomodulators (−)-Rapamycin and (−)-27-Demethoxyrapamycin: Assembly of the Common C(1−20) Perimeter and Final Elaboration
作者:Amos B. Smith、Stephen M. Condon、John A. McCauley、Johnnie L. Leazer、James W. Leahy、Robert E. Maleczka
DOI:10.1021/ja963067o
日期:1997.2.1
The potent, naturally occurring immunomodulators (−)-rapamycin (1) and (−)-27-demethoxyrapamycin (2) have been synthesized via a unified and highly convergent strategy. In the preceding paper we discussed the construction of common building blocks A−C and their linkage to provide the C(21−42) segments of 1 and 2. Herein we describe model studies of triene generation and hydroxyl deprotection, the preparation
Rapamycin synthetic studies. 2. Elaboration of the C(10)-C(26) perimeter
作者:Amos B. Smith、Robert E. Maleczka、Johnnie L. Leazer、James W. Leahy、John A. McCauley、Stephen M. Condon
DOI:10.1016/s0040-4039(00)73280-1
日期:1994.7
The C(10)-C(26) subunit of the potent immunomodulator rapamycin has been constructed via a highly convergent approach, exploiting palladium-mediated σ-bond formation to generate the sensitive triene moiety.