Reactions of Chiral 2-(tert-Butyl)-2H,4H-1,3-dioxin-4-ones Bearing Functional Groups in the 6-Position and Diastereoselective Catalytic Hydrogenation tocis-2,6-Disubstituted 1,3-Dioxan-4-ones
作者:Yoshihiro Noda、Dieter Seebach
DOI:10.1002/hlca.19870700819
日期:1987.12.16
(R)-5-Bromo-6-(bromomethyl)-2-(tert-butyl)-2H,4H-1,3-dioxin-4-one (2) derived from (R)-3-hydroxybutanoic acid is used for substitutions and chain elongations at the side-chain C-atom in the 6-position of the heterocycle (3–6, 10–13). Subsequent simultaneous reductive debromination and double-bond hydrogenation (Pd/C,H2)occurs with essentially complete diastereoselectivity (>98% ds), with H transfer from
(R)-5-溴-6-(溴甲基)-2-(叔丁基)-2 H,4 H -1,3-二恶英-4-酮(2)衍生自(R)-3-羟基丁酸用于置换和链伸长在杂环(的6位上的侧链C-原子3-6,10-13)。随后发生的同时还原性脱溴和双键加氢(Pd / C,H 2)基本上完全是非对映选择性(> 98%ds),并且H从与t- Bu组相反的一侧转移(15–20,表1))。然后,二恶烷酮的水解裂解产生对映体纯的β-羟基酸衍生物(3-羟基丁酸的立体中心整体自我复制或在该酸的4-位烷基化并保留构型)。
Brominations of Cyclic Acetals from ?-Amino Acids and ?- or ?-Hydroxy Acids withN-Bromosucinimide
作者:J�rg Zimmermann、Dieter Seebach
DOI:10.1002/hlca.19870700423
日期:1987.7.8
or 2-amino-carboxylic acids are treated with N-bromosuccinimide under typical radical-chain reaction conditions (azoisobuytyronitril/CCl4/reflux). Products of bromination in the α-position of the carbonyl group of the five-membered-ring acetals are isolated or identified (2, 5, and 8; Scheme 1). The dioxanones are converted to 2H, 4H-dioxinones under these conditions (12, 14, 15, 21, and 22; Schemes
Modified Preparation of (2<i>R</i>)-2-<i>tert</i>-Butyl-6-methyl-4<i>H</i>-1,3-dioxin-4-one; a Chiral Acetylacetic Acid Derivative for the Synthesis of Enantiopure Compounds
作者:Dieter Seebach、Urs Gysel、Kurt Job、Albert K. Beck
DOI:10.1055/s-1992-34162
日期:——
An improved synthesis of the title compound in ca. 45% yield on up to a 174 mmol scale is reported. Bromination of (2R,6R)-2-tert-butyl-6-methyl-1, 3-dioxan-4-one gives a mixture of mono- and dibromides which must be purified by chromatography to remove impurities which may poision the palladium catalyst in the following dehalogenation step.
Convergent synthesis of vineomycinone B2 methyl ester
作者:Marcus A. Tius、Xue Qin Gu、Jorge Gomez-Galeno
DOI:10.1021/ja00178a065
日期:1990.10
The characteristic features of vineomycinoneB2 (1) are the C-glycosyl bond to the olivose derivative, and the alkyl chain bearing a stereogenic center on the opposite side of the molecule. We report a triply convergent totalsynthesis of 1 which exploits methodology developed earlier in this group
Compounds of the formulae:
wherein R¹, R², R³ and R⁴ have a wide range of values are described as useful intermediates in the preparation of pharmaceuticals, etc, in particular in the preparation of optically active β-hydroxy α-substituted carboxylic acids. Processes for their preparation are described.