Atmospheric pressure chemical ionization multi-stage mass spectrometry in the characterization of stereoisomeric synthons of cyclopropane amino acids
摘要:
The mass spectrometric behaviour of (1S,2R)-, (1R,2R)-, (1R,2S)- and (1S,2S)-2-[(S)-2,2-dimethyl-1, 3-dioxolan-4-yl]-1-spiro-¿4'[2'-phenyl-5'(4'H)-oxazolone]¿ cyclopropane (2) and (1S,2R)-, (1R,2R)-, (1R,2S)- and (1S, 2S)-methyl-1-benzamido-2-[(S)-2,2-dimethyl-1, 3-dioxolan-4-yl]cyclopropanecarboxylate (3) was studied under atmospheric pressure ionization conditions and by multi-stage mass spectrometric (MS(n)) experiments performed with an ion trap. Interestingly, by using methanol as solvent, compounds 2 lead to [M + H + CH(3)OH](+) ions which, as proved by collisional experiments, exhibit the same structure of the corresponding compound 3. MS/MS of [MH](+) ions allows a clear characterization of the different stereoisomers, which give rise to specific fragmentation pathways, rationalized with respect to the structure of the neutral molecules.
1,3-Dipolar cycloaddition of diazomethane with a chiral azlactone
摘要:
The chiral Z-azlactone derived from 1,2-O-isopropylidene-D-glyceraldehyde reacted with diazomethane to afford stereoselectively and diastereoselectively a cis spiro-azlactone. Solvent and temperature dependence of the ratio of the products is described
Study of the reaction of a chiral oxazolone with oxosulphonium methylides as cyclopropanating agents
作者:Carlos Cativiela、María D. Díaz-de-Villegas、Ana I. Jiménez
DOI:10.1016/0040-4020(95)00033-5
日期:1995.3
The behaviour of the chiral Z-oxazolone derived from 1,2-O-isopropylidene-D-glyceraldehyde towards oxosulphoniummethylides as cyclopropanatingagents has been studied. The solvent and temperature dependence of the ratio of the products is described.
1,3-Dipolar cycloaddition of diazomethane to chiral azlactones. Experimental and theoretical studies
作者:Carlos Cativiela、María D. Díaz-de-Villegas、JoséI. García、Ana I. Jiménez
DOI:10.1016/s0040-4020(97)00120-8
日期:1997.3
The reaction of (E)-2-phenyl-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxazolone with diazomethane has been studied under a variety of reaction conditions, and the results compared with those obtained with the corresponding (Z)-isomer. The origin of the high diastereofacial selectivity in the cyclopropane products, observed with both oxazolones, is discussed in the light of theoretical calculations
A simple synthesis of (−)-(1S,2R)-allocoronamic acid in its enantiomerically pure form
作者:Carlos Cativiela、María D. Díaz-de-Villegas、Ana I. Jiménez
DOI:10.1016/0957-4166(94)00373-j
日期:1995.1
(−)-(1S,2R)-Allocoronamic acid was synthesized in its enantiomerically pureform by starting from the chiral azlactone derived from 1,2-O-isopropylidene-D-glyceraldehyde in an overall yield of 37 %.