Diastereofacial selection in nitrile oxide cycloaddition reactions. The anti-directing effect of an allylic oxygen and some new results on the ring metalation of isoxazolines. A synthesis of (.+-.)-blastmycinone
作者:Alan P. Kozikowski、Arun K. Ghosh
DOI:10.1021/jo00189a024
日期:1984.7
the adducts to known γ-lactones. The stereochemistry associated with the metalation/alkylation of 5-alkoxymethyl-substituted isoxazolines has also been probed in order to further expand the use of these heterocycles as aldol equivalents in natural products total synthesis. A synthesis of (±)-blastmycinone (34) is reported which combines the two foregoing aspects of stereocontrol. The levels of regio-
[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)-blastmycinone. Preliminary Communication
作者:Georg Fráter、Urs Müller、Wulf Günther
DOI:10.1002/hlca.19860690813
日期:1986.12.10
[2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis-ethyl propenylether showed a ca. 3:1 diastereo-selectivity. A two-step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)-compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis- benzyl 1-hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute
[2 + 2](薄荷基氧基)甲基乙烯酮(2)与顺式-乙基丙烯基醚的环加成反应显示为ca。3:1非对映选择性。热力学上更稳定的加合物4的两步转化使(2 R *,3 R *)化合物5的分子量约为1。50%ee(方案1)。与顺式-苄基1-己烯基醚(9)和2的类似反应序列显示出约1 。10和11中的5:1非对映选择性(方案2)。在C(3)和C(4)的绝对构型11( - ) - blastmycinone已经通过将其转换到证明。因此,优选的过渡状态被推导为15。
Enantioselective Syntheses of (+)- and (−)-Blastmycinolactol
Acyclic stereoselection. 12. Double stereodifferentiation with mutual kinetic resolution. A superior class of reagents for control of Cram's rule stereoselection in synthesis of erythro-.alpha.-alkyl-.beta.-hydroxy carboxylic acids from chiral aldehydes
作者:Clayton H. Heathcock、Michael C. Pirrung、John Lampe、Charles T. Buse、Steven D. Young
DOI:10.1021/jo00324a017
日期:1981.5
Highly stereo and regiocontrolled synthesis of both racemic and optically active (−)-blastmycinone