120 research outputs found
Synthesis of Aryl-sulphinyl Acetic Acids and Sulphoximides, and CD of their in situ Complexes with [MO2(OAc)4]
The syntheses of several optically active aryl-sulphinyl acetic acids and sulphoximides are described. They all give two or more Cotton effects in the presence of the metal cluster [MO2(OAc)4]in DMSO solution above 300 nm, from which their absolute configuration can be determined unequivocally
Circular Dichroism of Optically Active 1,4-Benzodiazepines
Assignment of the CD-bands of 1,4-benzodiazepin-2-one derivatives
(1-14, 26), and their 2-deoxo-congeners (15-25) has
been performed by applying the qualitative MO theory and the
exc1iton coupling theory. It has been found that the longest wavelength
band (about 310 nm), as well as that around 250 nm correspond
to the B2u and B1u transition of the chiral partial chromophore
A, respectively, while the corresponding transitions for the
partial chromophore C give rise to the bands at 285 nm and 250 nm
(Figures 2-4). The CD-signs for several of these Cotton effects
can be derived in a nonempirical manner. 7-Nitro derivatives,
23-25 scape above analysis, however, since the nitro-group is a
very strong perturber, which has its own absorption bands in the
same region. Model cyclic and acyclic compounds 27-36 have
been prepared, and their CD-spectra analysed in the same way
Attempted Diastereoselective Preparation and Chiroptical Properties of (2S)-1-(3-Mercapto-2-Methyl-1-Oxopropyl)-L-Proline (Captopril) and Some Congeners
CD and 13C-NMRstudy of the eonformational properties of (2S)-1-(3-mercapto-2-methyl-1-oxopropyl)-L-proline (captopril, 1), and its congeners 2-5, 8, 9 is reported. 13C-NMRdata (in DMSO-d6) reveal an E/Z (cis/trans) ratio of ea. (15-30) : (70-85) for the N-acetyl-prolines 1, 5, 10, and for N-acetyl-L-proline. CD data indicate practically identical conformations for the ring systems of 8 and 9. Attempted diastereoselective cyclization of the sodium salt of 7 or the free thioacid into 8 and 9 resulted in low chemical yields (-30%) and low diastereoselectivity, favouring formation of the »wrong- diastereomer 9 in small excess (-20%)
Biocatalytic preparation and absolute configuration of enantiomerically pure fungistatic anti-2-benzylindane derivatives. Study of the detoxification mechanism by Botrytis cinerea
Enantiomerically pure 2-benzylindane derivatives were prepared using biocatalytic methods and their
absolute configuration determined. (1R,2S)-2-Benzylindan-1-ol ((1R,2S)-2) and
(S)-2-benzylindan-1-one ((S)-3) were produced by fermenting baker’s yeast. Lipase-mediated
esterifications and hydrolysis of the corresponding racemic substrates gave rise to the enantiopure
compounds (1S,2R)-2-benzylindan-1-ol ((1S,2R)-2) and (1R,2S)-2-benzylindan-1-ol ((1R,2S)-2),
respectively. The antifungal activity of these products against two strains of the plant pathogen Botrytis
cinerea was tested. The metabolism of anti-(±)-2-benzylindan-1-ol (anti-(±)-2) by B. cinerea as part of
the fungal detoxification mechanism is also described and revealed interesting differences in the genome
of both strains
About the absolute configuration of cantharsäure and palasonins
The absolute configurations of (+)-cantharic acid, a chiral derivative of the achiral insect defensive substance cantharidin (1), and of palasonin, a lower homologue of 1 occurring in the plant Butea frondosa, were shown to be represented by formulas 2 and 3, respectively (scheme 1). These results were obtained by application of the Horeau method (table 1) on the (+)-cantharic acid derivatives (+)-5, (-)-7, and (-) 11 (scheme 2), and the palasonin derivatives (+)-29 and (+)-30 (scheme 4), as well as by comparison of the chiroptical properties (tables 2 and 3) of a number of derivatives, prepared from either cantharic acid or palasonin. - Attempts to incorporate various radioactively labelled precursors into palasonin (3), using young and adult plants, have been so far unsuccessful
- …