Asymmetric aza Diels-Alder reactions of amino acid ester imines with Brassard's diene
摘要:
Imines 1 obtained from aromatic, aliphatic or functionalized aldehydes and valine tert-butyl ester undergo Lewis acid catalyzed hetero Diels-Alder reactions with Brassard's diene 2. The cycloadducts are formed in good to high yields and with diastereomer ratios of 92:8-97:3. For the removal of the chiral auxiliary group a new method was developed whose principle consists in the conversion of the amino acid alpha-C-atom into an acetalic center employing a Curtius rearrangement as the key step.
acceptors. The optimum conditions identified herein were successful in the oxidation of various types of primary alcohols, including unprotected amino alcohols and divalent-sulfur-containing alcohols in good-to-high yields. Moreover, N-protected alaninol, an inefficient substrate in the nitroxyl radical/copper-catalyzedaerobicoxidation, was oxidized in good yield. On the basis of the optimization results
Zinc-copper(I) chloride or -silver acetate promoted coupling reaction of 2-[(Trimethylsilyl)methyl]-3-chloro-3,3-difluoropropene with carbonyl compounds. Highly efficient access to 2,2-difluoro homoallyl alcohols
2-[(Trimethylsilyl)methyl]-3-chloro-3,3-difluoropropene, readily prepared in two steps from methyl chlorodifluoroacetate and (trimethylsilyl)methylmagnesium chloride, is reduced to couple regioselectivity with a variety of carbonylcompounds in the presence of zinc-copper(I) chloride or -silver acetate to give 2,2-difluoro-3-[(trimethylsilyl)methyl]-3-buten-1-ol derivatives in good to excellent yields
Stereospecific CC-bond formation with rabbit muscle aldolase - A chemoenzymatic synthesis of (+)-exo-brevicomin
作者:M. Schultz、H. Waldmann、W. Vogt、H. Kunz
DOI:10.1016/s0040-4039(00)94649-5
日期:1990.1
(+)-(1S,5R,7S)-Exo-brevicomin 9, a sex pheromone of the western pine bark beetle, is synthesized using an aldol reaction catalyzed by fructose-1,6-diphosphate aldolase (EC 4.1.2.13) from rabbitmuscle as the key step by which the absolute configuration of the target is established.
Bicyclo[3.2.1] type 1,2,4-trioxanes are readily synthesized from precursors that may form intramolecular hemiketals using UHP (H2O2-urea complex) as the source of the peroxy bond and p-TsOH or CSA as the catalyst. The ring closure through an intramolecular Michael addition occurred in a highly stereoselective way, giving only one diasteromer as shown by the NMR spectra. (c) 2006 Elsevier Ltd. All rights reserved.
SCHULTZ, M.;WALDMANN, H.;VOGT, W.;KUNZ, H., TETRAHEDRON LETT., 31,(1990) N, C. 867-868