Сообщение
Phobos » Ср дек 11, 2019 1:26 pm
Гляньте сюда:
A three-step synthesis (±)-β-methyleneaspartic acid
By Hand, Elli Smakula; Baker, David C.
From International Journal of Peptide & Protein Research (1984), 23(4), 420-4.
A simplified, 3-step synthesis for (±)-β-methyleneaspartic acid (I) is described. Condensation of di-Et malonate with Et pyruvate gave 1,1,2-tricarbethoxyprop-1-ene, which was α-aminated with chloramine to give 1-amino-1,1,2-tricarbethoxyprop-2-ene. The latter was hydrolyzed in acid to give I.
Тут, к сожалению, в обзоре не указаны условия конденсации, возможно, это тот же ZnCl2/Ac2O. Но проверьте.
Improved varients of the Knoevenagel condensation with titanium tetrachloride-THF-pyridine. I. Alkylidene- and arylideremalonic esters at 0-25.deg.
By Lehnert, Willy
From Tetrahedron Letters (1970), (54), 4723-4. | Language: German, Database: CAPLUS
Yields in the Knoevenagel condensation were increased to 73-100% by carrying out the reaction in the presence of TiCl4 and pyridine in THF or dioxane at 0-25°. RCH:C(CO2Et)2 (where R = Me, Et, Pr, Bu, MeCH:CH, Ph, substituted phenyl, 2-furyl, or 2-thienyl), EtO2CCMe:C(CO2Et)2, and (EtO2C)2C:C(CO2Et)2, and (EtO2C)2C:CHC6H4CH:C(CO2Et)2 were prepd.
А вот это может стать альтернативой.
Возможно, Ваш продукт слишком активный Михаэль-акцептор, и в основных условиях он начинает бодро реагировать с малонатом вместо пирувата. Поэтому и делают эту конденсацию с к-тами Льюиса.
Еще приготовление триметилового сл. эфира описано здесь, но вместо пировата какой-то другой субстрат. Если хотите, пoпытайтесь понять из обзора:
Synthesis of substances analogous to bile acid degradation products. II. Synthesis of some straight-chain polycarboxylic esters
By Baker, John W.
From Journal of the Chemical Society (1933), 811-15. | Language: Unavailable, Database: CAPLUS
cf. C. A. 25, 4530. In an attempt to synthesize cholane, a study was made of straight-chain esters of the type (MeO2C)2CHCMe(CO2H)C(CO2Me)2C(CO2Me)2CHMeCH2CH2CO2Me, which should, by the application of the Dieckmann reaction, afford the desired cyclopentanone ester. The 2 component esters have been prepd. but the best means of uniting them has to be worked out. CHNa(CO2Me)2 and Me γ-bromovalerate give Me β-methylbutane-α,α,δ-tricarboxylate (I), b3 145°. Me α-bromopropionate gives Me propane-α,α,β-tricarboxylate (II), m. 48-9°; triamide, m. 249° (decompn.); amide-imide, m. 162°; Br gives the α-Br deriv., b7 150°; CHNa(CO2Me)2 gives II; C5H5N gives Me Δα-propene-α,α,β-α,α,β-tricarboxylate, b53 178°; amide, m. 198° (decompn.); with MeONa acid products were obtained; HBr-AcOH gives Me β-bromopropane-α,α,β-tricarboxylate (III), b5 158-65°, m. 68°; the corresponding I deriv. b10 165-75°, m. 72°. III and CHNa(CO2Me)2 give Me β-methylpropane-α,α,β,γ,γ-pentacarboxylate, m. 58°. In an attempt to condense I with III by means of MeONa there resulted Me β,γ-dimethylbutane-α,α,β,γ,δ,δ-hexacarboxylate, m. 179°. AcCHNaCO2Me and Me α-bromopropionate give Me β-ketopentane-γ,δ-dicarboxylate, b30 146°; semicarbazone, m. 159°. Et ethane-α,α,β-tricarboxylate and Et bromosuccinate in EtONa give Et butane-α,β,γ,γ,δ-pentacarboxylate, b5 210°; Et β-bromopropane-α,β-dicarboxylate did not give the desired condensation product. Et γ-bromo-β-methylpropane-α,γ,γ-tricarboxylate b9 184°; this did not condense with the K deriv. of Et α,β-dicyano-β-methylglutarate (IV). Hydrolysis of IV with EtOH-HCl and a little H2SO4 gives a compd., m. 109-10°, further hydrolyzed by concd. HCl to an acid, m. 133°, which may be the pyridine deriv. C7H9O4N.
Wodka trinkt man pur und kalt, das macht hundert Jahre alt!
.
