Search

FEW investigations of the utilization of metal chelate compounds for the optical resolution of racemic compounds have so far been reported1–4. DL-Aspartic acid copper complex was optically resolved completely from its supersaturated solution by seeding it with D- or L-aspartic acid copper complexes1. Bailar et al. first reported the stereo-specific (stereoselective) ligand exchange reaction2, and later they reported the partial optical resolution of DL-alanine by use of the reaction of DL-alanine with copper glutamate (optical purity 3.3 per cent3). Recently, Shibata et al.4 reported the partial optical resolution of DL-alanine in 25.6 per cent optical purity by use of the aspartic acid cobalt(III) complex.

Electroreductive coupling of Schiff bases with alkyl halides to form amino acids was carried out using constant potential electrolysis.

The glycine residue in N-salicylideneglycyl-L-valinatocopper(II) reacts with formaldehyde in aqueous solution at pH 8·5 and the resulting complex gives seryl-L-valine containing optically active serine.

Carbonaceous chondrites contain extraterrestrial organic compounds. Because of little contamination by terrestrial organic matter, we focused our analyses on Antarctic carbonaceous chondrites, Carbon vs nitrogen contents of 10 carbonaceous chondrites yielded a straight line relation in a log-log diagram. It seems that the two contents change almost continuously from CI to C3 chondrites rather than discrete distribution on the types of the chondrites. This straight line relation indicates that the ratio is not constant but increases as the contents of organic compounds decreases. Our estimate shows the ratio is about 11 at the boundary between CI abd C2 chondrites and about 25 between C2 and C3. Extrapolation of the relation toward more primitive than CI chondrites enables to estimate the contents of carbon and nitrogen in such a condensate. Analyses of the Yamato-791198(C2) showed that this chondrite yielded the most abundant amino acids analyzed so far. On the other hand, the Yamato-793321 and Belgica7904 contained no detectable amount of amino acids, in spite of the appropriate abundances of carbon and nitrogen as C2 chondrites. Although there remains a possibility that the depletion of amino acids was due to Antarctic-water washing, it might be caused during the organic formation in the early nebular process. The Yamato-791198 was further analyzed for other organic compounds. Analyses of carboxylic acids showed the presence of acetic to C12 acid in the aliphatic portion with various structural isomers of C 4 to C 7 acids. Some of these organic acids were found at the same level of the concentration as amino acids. Aliphatic and aromatic hydrocarbons were also present in the chondrite. These results of analyses of organic compounds will be discussed in detail together with our postulate of the primitive condensate.

‘Racemic’ piperazine-2,5-diones (diketopiperazines, dkps) have been synthesized by the self-condensation of DL-amino acid esters without solvent. It was found that ‘racemic’ dkps consisted of cis- and trans-isomers, and that cis-dkp was preferentially formed in the early stage of the self-condensation, the cis : trans ratios gradually decreasing with increasing reaction time. These results may be attributed to the difference in the rates of cyclization of two kinds of diastereoisomeric dipeptide esters, intermediates in the formation of dkps from DL-amino acid esters. It was further confirmed that the pre-cis-dipeptide ester, which formed cis-dkp, cyclized faster than the pre-trans-dipeptide ester in methanol. Differences in steric hindrance in the cyclization reaction of pre-cis- and pre-trans-isomers may be an important factor in the stereochemistry of self-condensation.

The alkyl 1-alkylaziridine-2-carboxylates (III) have been asymmetrically synthesized from the alkyl αβ-dibromopropionates (I) and chiral benzylamines (II); optically active serine (V) was obtained by hydration of (III).

Gel permeation chromatographic studies of poly(ethylene glycol) degraded in 0.002M NaCl solution by glow discharge electrolysis suggest that cleavage of the polymer chain takes place only in a localized zone of the reaction system.

Cellulose ion exchanger palladium catalysts preparation and applications in asymmetric hydrogenation reactions

ASYMMETRIC adsorption of organic compounds on bio-polymers such as polysaccharides1–7, wool8,9 and casein9 has been reported, but the resulting optical activities of these were usually very low and the capacity for adsorption was very small. On the other hand, several studies of optical resolution by preferential crystallization have been reported (reviewed in ref. 10). Recently, DL-aspartic acid copper complex11, DL-aspartic acid, DL-glutamic acid, DL-asparagine and DL-glutamine12 have been resolved almost completely by the preferential crystallization method in our laboratory.

RESOLUTION by inoculation of a supersaturated solution with one enantiomorph has been discussed by Greenstein1. More recently, the resolution of glutamic acid by inoculation has been perfected for industrial use2,3.

Asymmetric synthesis of alanine by hydrogenolytic asymmetric transamination, noting temperature effect

When hot saturated solutions of thermal copolymers containing the 18 common amino acids are allowed to cool, huge numbers of uniform, microscopic, relatively firm, and elastic spherules separate. The place of this phenomenon in a comprehensive theory of original thermal generation of primordial living units is considered.