Total Synthesis of (+)-Calyculin A and (-)-Calyculin B: Asymmetric Synthesis of the C(9-25) Spiroketal Dipropionate Subunit

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• 作者：Amos B. Smith ; III ; Gregory K. Friestad ; Joseph Barbosa ; Emmanuel Bertounesque ; Kenneth G. Hull ; Makoto Iwashima ; Yuping Qiu ; Brian A. Salvatore ; P. Grant Spoors ; and James J.-W. Duan
• 刊名：Journal of the American Chemical Society
• 出版年：1999
• 出版时间：November 17, 1999
• 年：1999
• 卷：121
• 期：45
• 页码：10468 - 10477
• 全文大小：872K
• 年卷期：v.121,no.45(November 17, 1999)
• ISSN：1520-5126

文摘

An asymmetric synthesis of the stereochemically fully endowed C(9-25) spiroketal fragment (+)-BC of the calyculins (1-8) is described. Highlights of the synthesis include: a highly diastereoselective IBr-induced iodocarbonate cyclization to introduce the C(21) stereocenter in epoxide (+)-18, fragment unionsexploiting the reaction of acyl anion equivalents with epoxides to construct masked advanced aldols (-)-35and (+)-71 as single diastereomers, chelation-controlled addition of the C(14-15) vinyl group to aldehyde(+)-38 to set the stereogenicity at C(16), selective reduction of the C(13) ketone via 1,3-induction, anddevelopment of an orthogonal protection scheme permitting both convenient installation of the C(17) phosphategroup and flexibility in subsequent fragment couplings.