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71.
Teng-Kuei Yang Dong-Sheng Lee Tsung-Fan Teng Ting-Ting Jong Mei-Yueh Chien 《中国化学会会志》1991,38(4):401-403
Introducing two chiral auxiliaries, sulfoxide and menthol, into an acrylate would have either matched or mismatched pair systems. The presence of chiral menthol in α-sulfinylacrylates can change the diastereoselectivity from 24% d.e. to a single diastereomer by manipulation of the double asymmetric strategy. 相似文献
72.
A new method for the preparation of the synthon (±)-2,6,7,7a-tetrahydro-1β-hydroxy-4-formyl-7aβ-methylindene (1,a) for the
total synthesis of steroids in both (±) and (+) forms, starting from the known β-ketoester, (±)-methyl 1β-t-butoxy-5,6,7,7a-tetrahydro-7aβ-methyl-5-keto-4-indancarboxylate (2,a) has been described. An alternative route to (1,a) has
been investigated. Although the compound, (±)-1β-hydroxy-5,6,7,7a-tetrahydro-7aβ-methyl-5-keto-4-methoxymethylindan (2,b)
could not be prepared, interesting pathways leading to two unexpected products, (±)-5,6,7,7a-tetrahydro-4,7a-dimethyl-5H-indene-1,5-dione
and (±)-2,6-diketo-3-methyltricyclo-(5,2,1,0)decan-8-ol (3 and 4), were encountered during an attempted annelation reaction
of the ketone, N-diethylamino-5-methoxypentan-3-one (6), with 2-methylcyclopentan-1,3-dione (5). Trapping of the intermediate,
(±)-3a,4,5,6,7,7a-hexahydro-3a-hydroxy-4-methylene-7a-methylindene-1,5-dione (7), through the formation of the adduct, (±)-3a,4,5,6,7,7a-hexahydro-3a-hydroxy-4-(1′,
3′-diketo-2′-methylcyclopentano-2′-methylene)-7a-methylindene-1,5-dione (8), established the mechanism of the formation of
the products (3 and 4). 相似文献
73.
本文综述了近年来四氧化锇催化烯烃不对称双羟化及其反应机理的研究进展。Sharpless等对烯烃双羟化机理的透彻研究导致了不对称双羟化方法的优化。 相似文献
74.
Keum SR Roh HJ Choi YK Lim SS Kim SH Koh K 《Magnetic resonance in chemistry : MRC》2005,43(10):873-876
(1)H and (13)C NMR spectra of symmetric and asymmetric bis-spiropyrans, Series 1-3, were completely assigned. Especially, the (1)H assignment of asymmetric spiropyrans was achieved by utilizing (1)H-(1)H COSY and nOe experiments. All of the carbons in the dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR), together with an attached proton test (APT). 相似文献
75.
The asymmetric 1,2-addition of trimethylsilyl cyanide to aldehyde SAMP-hydrazones in the presence of titanium tetrachloride and diethylether in dichloromethane at −100°C up to room temperature, removal of the chiral auxiliary and acid hydrolysis affords α-amino acids in high enantiomeric excesses (ee=94-97%). 相似文献
76.
77.
78.
环己胺与手性元5-(R)-(1′R,2′S,5′R)-孟氧基-3-溴-2(5H)-呋喃酮的不对称M ichael加成/分子内亲核取代反应,得到含有两个新手性中心的氮杂环丙烷/稠合丁内酯标题化合物。对其进行了谱学表征和X-射线单晶衍射测定。标题化合物分子式为C20H33NO3,M r=335.47,三斜晶系,P1空间群,晶胞参数:a=5.438(11)。A,b=8.117(2)。A,c=11.572(2)。A,α=96.84(3)°,β=94.48(3)°,γ=101.86(3),°V=493.5(2)。A3,Z=1,D c=1.129g/cm3,R=0.0867,wR=0.2344。 相似文献
79.
Yuri N. Belokon’Devayani Bhave Daniela D'AddarioElizabetta Groaz Viktor MaleevMichael North Armine Pertrosyan 《Tetrahedron letters》2003,44(10):2045-2048
Copper(salen) complex 1 has been found to catalyse the asymmetric alkylation of enolates derived from a variety of amino acids. There is a clear relationship between the size of the side chain in the substrate and the enantioselectivity of the process, so that the enantioselectivity decreases in the order alanine>aminobutyric acid>allylglycine>leucine>phenylalanine>valine. A transition state model which accounts for the influence of the size of the side chain on the enantioselectivity of the reactions is presented. 相似文献
80.