We developed neutral iridium catalysts with chiral spiro phosphine-carboxy ligands (SpiroCAP) for asymmetrichydrogenation of unsaturated carboxylic acids. Different from the cationic Crabtree-type catalysts, the iridium catalysts with chiral spiro phosphine-carboxy ligands are neutral and do not require the use of a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF−) counterion, which is necessary
An additive-free enantioselective hydrogenation of β,β-disubstituted unsaturated carboxylicacids catalyzed by the Rh–(R,R)-f-spiroPhos complex has been developed. Under mild conditions, a wide scope of β,β-disubstituted unsaturated carboxylicacids were hydrogenated to the corresponding chiral carboxylicacids with excellent enantioselectivities (up to 99.3% ee). This methodology was also successfully
Asymmetric conjugate addition reaction by the use of ()-γ-trityloxymethyl-γ-butyrolactam as a chiral auxiliary
作者:Kiyoshi Tomioka、Toshiro Suenaga、Kenji Koga
DOI:10.1016/s0040-4039(00)84021-6
日期:1986.1
(S)-γ-Trityloxymethyl-γ-butyrolactam (2) serves as a chiralauxiliary in the conjugate addition reaction of the corresponding imide (3) of α,β-unsaturated carboxylic acids with Grignard reagents in the presence of CuBrSMe2 in THF to give, after hydrolysis, the β,β-disubstituted carboxylic acids (5) with predictable absolute configuration and high enantiomeric excess.
A set of chiral imidazolylpropylguanidines and 2-aminothiazolylpropylguanidines bearing N-G-3-phenyl- or N-G-3-cyclohexylbutanoyl residues was synthesized and investigated for histamine H-2 receptor (H2R) agonism ( guinea pig (gp) right atrium, GTPase assay on recombinant gp and human (h)H2R) and for hH(2)R selectivity compared to hH(1)R, hH(3)R and hH(4)R. In contrast to previous studies on arpromidine derivatives, the present investigation of acylguanidine-type compounds revealed only very low eudismic ratios (1.1-3.2), indicating the stereochemistry of the acyl moiety to play only a minor role in this series of H2R agonists. (C) 2010 Elsevier Ltd. All rights reserved.
Levene; Marker, Journal of Biological Chemistry, 1935, vol. 110, p. 329,341