Letter: Studies on the biosynthesis of beta-lactam antibiotics. I. Synthesis of(2RS,3S)-(4,4,4-2H3)valine.
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Anti-Bacterial Agents↗
Biomedical subjects
L J Lin
Publications and source records attributed to L J Lin.
Oxidation and cleavage of 3-aminopyridine adenine dinucleotide phosphate with periodate.
Treatment of 3-aminopyridine adenine dinucleotide phosphate with sodium periodate in the neutral pH resulted in oxidation of the ribose linked to 3-aminopyridine and cleavage of the dinucleotide into adenosine- and 3-aminopyridine-containing moieties. Separation of these moieties was afforded by thin-layer chromatography, high-performance liquid chromatography, and fast protein liquid chromatography. From fast atom bombardment mass spectra and nuclear magnetic resonance spectra, the adenosine-containing moiety was identified as 2'-phosphoadenosine 5'-phosphate while the aminopyridine moiety was present in a mixture of the hydrated 3-aminopyridine mononucleotide/nucleoside dialdehyde. Separation of the completely oxidized product by Pharmacia fast protein liquid chromatography gave three major peaks corresponding to 2'-phosphoadenosine 5'-phosphate, 2'-phosphoadenosine 5'-diphosphate and oxidized 3-aminopyridine nucleoside, with minor amount of oxidized 3-aminopyridine mononucleotide. Thus the oxidized 3-aminopyridine adenine dinucleotide phosphate was shown to cleave by two pathways: it may either undergo beta-elimination to give 2'-phosphoadenosine 5'-diphosphate and oxidized 3-aminopyridine nucleoside; or the phosphodiester linkage may be hydrolyzed to give 2'-phosphoadenosine 5'-phosphate and oxidized 3-aminopyridine mononucleotide. The latter compound may further undergo beta-elimination and eventually give oxidized 3-aminopyridine nucleoside. Hydrolysis could be prevented by storing the sample as lyophilized powder, while beta-elimination was diminished by lowering the storage temperature. We found that the lyophilized powder of oxidized 3-aminopyridine adenine dinucleotide phosphate can be stored at -50 degrees C for several months with minimum decomposition.
Chromatography, High Pressure Liquid↗
The dermatitis-producing constituents of Euphorbia hermentiana latex.
Five ingenane derivatives, 3-O-n-(deca-2,4,6-trienoyl)-16-O-[(Z)-2-methyl-2-butenoyl]-16-hydroxyingenol (1), 3-O-[(Z)-2-methyl-2-butenoyl]-5,16,20-O-triacetyl-16-hydroxyingenol (2), 3-O-[(Z)-2-methyl-2-butenoyl]-16,20-O-diacetyl-16-hydroxyingenol (3), 3-O-[(Z)-2-methyl-2-butenoyl]-20-O-acetylingenol (4), and 3-O-[(Z)-2-methyl-2-butenoyl]-16-O-acetyl-20-deoxy-16-hydroxyingenol (5) were isolated with a new procedure that uses droplet counter-current chromatography, from a dermatitis-producing fraction of the latex of Euphorbia hermentiana Lem. The structures of the new compounds 2,3, and 5 were established by the interpretation of their spectroscopic data and those of their hydrolytic and acetylated derivatives.
Animals↗
Nmr studies of colchicine and its photoisomers, beta- and gamma-lumicolchicines.
Unambiguous 1H- and 13C-nmr assignments of colchicine, beta-lumicolchicine, and gamma-lumicolchicine have been obtained using a combination of 1D- and 2D-nmr spectroscopic techniques. The data indicate that gamma-lumicolchicine is a stereoisomer of beta-lumicolchicine and provide definitive evidence for their stereochemical assignments.
Colchicine↗