The first asymmetric totalsynthesis of fluvirucinine A2 has been accomplished. A key feature of the synthesis is an iterative lactam ring expansion to provide rapid access to the 14-membered lactam skeleton and three stereogenic centers. The excellent remote control of the three stereogenic centers relied on stereoselective amidoalkylation followed by an amide−enolate-induced aza-Claisen rearrangement
Eine neue Synthese von (<i>S</i>)-β-Methyl-γ-butyrolacton und (<i>S</i>)-4-Benzyloxy-3-methylbutansäure
作者:Ulrich Berens、Hans-Dieter Scharf
DOI:10.1055/s-1991-26584
日期:——
A New Synthesis of (S)-β-Methyl-γ-butyrolactone and (S)-4-Benzyloxy-3-methylbutanoic Acid A stereoselective synthesis of (S)-β-methyl-γ-butyrolactone [(S)-4,5-dihydro-4-methyl-2(3H)-furanone, 1] and of (S)-4-benzyloxy-3-methylbutanoic acid (2) is described. Both compounds are prepared starting from inexpensive L-ethyl lactate with overall yields of 26% and 30%, respectively. The products are valuable chiral building blocks.
A C1-C6 fragment of pinnatoxin A, (5S,6R)-5,6-dimethyl-3-methyleneoxepan-2-one, which features a gamma,delta-trans-dimethyl-substituted alpha-methylene lactone, has been synthesized in an enantiomerically pure form from ethyl (E)-4-benzyloxy-2-butenoate through an auxiliary-based conjugate addition and alkylation reaction. The excellent diastereoselectivity (98:2) observed in the alkylation reaction is the result of stereocontrol from both the adjacent stereocenter and the chiral oxazolidinone. (C) 2008 Elsevier Ltd. All rights reserved.
SCHMID, RUDOLF;HANSEN, HANS-JURGEN, HELV. CHIM. ACTA, 73,(1990) N, C. 1258-1275
作者:SCHMID, RUDOLF、HANSEN, HANS-JURGEN
DOI:——
日期:——
Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)-Catalyzed Asymmetric Allylamine to Enamine Isomerization
作者:Rudolf Schmid、Hans-J�rgen Hansen
DOI:10.1002/hlca.19900730516
日期:1990.8.8
The application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5-isoprenoid allylic amines of types IId and IIe (Scheme 1) is described. It is shown that a number of such substrates can be isomerized with enantioselectivities of > 90% ee. using cationie Rh1 complexes containing (6. 6′-dimethylbiphenyl′2, 2′-diyl)bis(dipheny phosphine) (BIPHEMP; 9) as asymmetry-inducing