Total Synthesis of (+)-Calyculin A and (−)-Calyculin B: Asymmetric Synthesis of the C(9−25) Spiroketal Dipropionate Subunit
作者:Amos B. Smith、Gregory K. Friestad、Joseph Barbosa、Emmanuel Bertounesque、Kenneth G. Hull、Makoto Iwashima、Yuping Qiu、Brian A. Salvatore、P. Grant Spoors、James J.-W. Duan
DOI:10.1021/ja992134m
日期:1999.11.1
An asymmetricsynthesis 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 unions exploiting the reaction of acyl anion equivalents with epoxides to construct masked advanced
Practical, highly stereoselective allyl- and crotylsilylation of aldehydes catalyzed by readily available Cinchona alkaloid amide
作者:Yuan Huang、Licheng Yang、Panlin Shao、Yu Zhao
DOI:10.1039/c3sc50973g
日期:——
constructed based on the Cinchonaalkaloid structure that promote highly stereoselectivereactions of allyl- and crotyltrichlorosilane with aromatic as well as aliphatic aldehydes (90–99% ee, >98% diastereoselectivity). The catalysts are available in a one-pot procedure in >70% yield from cheap starting materials and promote the allylation reactions at ambient temperature. Gram scale reactions with catalyst recovery
Synthesis of the ABC Ring Fragment of Brevisin, a New Dinoflagellate Polycyclic Ether
作者:Kazuo Tachibana、Masayuki Satake、Naohito Ohtani、Ryosuke Tsutsumi、Takefumi Kuranaga、Tomohiro Shirai、Jeffrey L. C. Wright、Daniel G. Baden
DOI:10.3987/com-09-s(s)93
日期:——
A polycyclic ether, brevisin was isolated from the red-tide dinoflagellate Karenia brevis. Its unique skeletal structure consists of two separate tricyclic ether assemblies connected by a methylene bridge. The ABC ring fragment of brevisin was synthesized via Suzuki-Miyaura cross coupling toward a total synthesis of brevisin.
Calyculin synthetic studies. Stereoselective construction of the C(14)-C(25) spiroketal subunit
作者:Amos B. Smith、James J.-W. Duan、Kenneth G. Hull、Brian A. Salvatore
DOI:10.1016/s0040-4039(00)93479-8
日期:1991.9
A convergent, stereocontrolled synthesis of the spiroketal fragment of calyculins A-H has been achieved. Key transformations include the novel iodine monobromide-induced iodocarbonate cyclization of (+)-19, efficient coupling of epoxide (+)-14 with the sterically hindered dithiane 15, and a multi-step, one-pot conversion of open-chain precursor (-)-13 to spiroketal (+)-11.