Synthesis of dehydroindolizidine-type poison-frog alkaloids <i>via</i> Michael-type conjugate addition
作者:De-Jun Zhou、Xue-Yan Li、Dong Li、Zhong-Shuai Guo、Qin-Ling Zhang、Hong-yan Bie、Zheng-Guo Cui
DOI:10.3184/174751917x14967701766987
日期:2017.7
A concise stereoselective synthesis of proposed dehydroindolizidine-alkaloids of types 179 and 207E1 was accomplished via Michael-type conjugate addition. A comparison of natural 207E and synthesised compound 207E on GC–FTIR revealed the double bond of natural 207E is most likely at the 7,8-position.
1,3-Dioxanone Derivatives from ?-Hydroxy-carboxylic Acids and Pivalaldehyde. Versatile Building Blocks for Syntheses of Enantiomerically Pure Compounds. A Chiral Acetoacetic Acid Derivative Preliminary Communication
作者:Dieter Seebach、J�rg Zimmermann
DOI:10.1002/hlca.19860690523
日期:1986.7.30
(R)-3-Hydroxybutyric acid (from the biopolymer PHB) and pivalaldehyde give the crystalline cis - or (R,R)-2-(tert-butyl)-6-methyl-1,3-dioxan-4-one (1a), the enolate of which is stable at low temperature in THF solution and can be alkylated diastereoselectively (3, 4, 5, and 7). Phenylselenation and subsequent elimination give an enantiomerically pure enol acetal 10 of aceto-acetic acid. Some reactions of
1,4-Addition of grignard reagents and 1,6-addition of lithium organocuprates to n,n-diethylsorbamide
作者:F Barbot、A Kadib-Elban、Ph Miginiac
DOI:10.1016/s0040-4039(00)94048-6
日期:1983.1
When they react with N,N-diethylsorbamide, saturated and allylic Grignard reagents give γ,δ-ethylenic amides (1,4-addition) whereas saturated and allylic lithiumorganocuprates give β,γ-ethylenic amides (1,6-addition).
The opposite diastereoselectivity in the alkylation and protonation of enolates
作者:Yoshinori Yamamoto、Kazuhiro Maruyama
DOI:10.1039/c39840000904
日期:——
enoate (5) produces predominantly the syn-isomer (7) having the butyl and methyl groups syn on the carbon chain, while the methylation of the enolate derived from the ester (8) gives preferentially the other diastereoisomer, anti-(6); the diastereoselectivity can be explained by an eclipsed model.
A diastereoselective synthesis of 3,5-disubstituted indolizidines based on an intermolecular addition of an allylsilane on an acyliminium ion derived from (S)-pyroglutamic acid is described. The synthetic potential of this methodology is demonstrated by the enantioselective synthesis of (-)-indolizidine 195B, (-)-indolizidine 223AB, (+)-monomorine and (-)-3-butyl-5-propyl indolizidine. (c) 2006 Elsevier Ltd. All rights reserved.