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PubMed1985

Models of molecular evolution. 2. Stereospecificity of dipeptide syntheses by means of cyanamides and carbodiimides.

Acetyl, benzyloxycarbonyl and tosyl protected DL-alanine, DL-leucine, DL-methionine, DL-phenylalanine, and DL-valine were condensed with DL-amino acid methyl esters. Cyanamide, diethylcyanamide, diisopropyl carbodiimide, dicyclohexyl carbodiimide, and N-cyclohexyl-N'-(2-morpholino ethyl) carbodiimide-N''-methotosylate served as condensing reagents. Water, methanol, and dimethylformamide were used as reaction media. The stereochemical course of these dipeptide syntheses was elucidated by means of 13C-n.m.r. spectroscopy. The formation of L-L and D-D bonds (isotactic sequences) was favoured in ca. 80% of all condensations. L-L/L-D (D-D/D-L) ratios of up to 6:1 were found.

Dipeptides↗
PubMedDate not supplied

[Possible step in abiogenic molecular evolution].

Studies of peculiarities of sublimation of frozen solutions in small concentrations are described. Threadlike structures were revealed, whose formation can be explained by the development of spiral dislocations and aggregations of solved structure molecules into monomeric sequences of considerable length (up to 10(11) links). Possible coordination of molecules during the arrangement of closely located sequences from different biomonomeres is discussed. A hypothesis about sublimation mechanism of the organization of primary structure of macromolecules of the living matter is substantiated. This mechanism explains the appearance of genetic code and stereohomogeneity.

Ammonia↗