“…266,267 Hypoglycine B was shown to be the γ-L-glutamyl dipeptide 437 (Figure 10). 273,279,280 Several synthetic approaches to racemic hypoglycine A have been developed. Thus, cyclopropanation of 2-bromopropene (438) with ethyl diazoacetate under copper catalysis gave ethyl 2-bromo-2-methylcyclopropanecarboxylate (439), which was dehydrobrominated to ethyl 2-methylenecyclopropanecarboxylate (440).…”
Section: Hypoglycinementioning
confidence: 99%
“…Starting with the determination of its molecular formula, several research groups simultaneously elucidated the constitution of hypoglycine A to be 3-(2-methylenecyclopropyl)alanine, also referred to as α-amino(methylenecyclopropyl)propionic acid. ,,− The configuration of the α-carbon was evidenced to be 2 S , , and after an originally wrong assignment for the γ-carbon atom to have ( S )-configuration, natural hypoglycine A 436 (Figure ) was proven to be a diastereomeric mixture of the (2 S ,4 R )- and the (2 S ,4 S )-isomer with 17% diastereomeric excess in favor of the (2 S ,4 R )-isomer (Figure ). , Hypoglycine B was shown to be the γ- l -glutamyl dipeptide 437 (Figure ). ,, 10 Hypoglycine A and B. 77 Syntheses of Racemic Hypoglycine A 282,285-287 …”
“…266,267 Hypoglycine B was shown to be the γ-L-glutamyl dipeptide 437 (Figure 10). 273,279,280 Several synthetic approaches to racemic hypoglycine A have been developed. Thus, cyclopropanation of 2-bromopropene (438) with ethyl diazoacetate under copper catalysis gave ethyl 2-bromo-2-methylcyclopropanecarboxylate (439), which was dehydrobrominated to ethyl 2-methylenecyclopropanecarboxylate (440).…”
Section: Hypoglycinementioning
confidence: 99%
“…Starting with the determination of its molecular formula, several research groups simultaneously elucidated the constitution of hypoglycine A to be 3-(2-methylenecyclopropyl)alanine, also referred to as α-amino(methylenecyclopropyl)propionic acid. ,,− The configuration of the α-carbon was evidenced to be 2 S , , and after an originally wrong assignment for the γ-carbon atom to have ( S )-configuration, natural hypoglycine A 436 (Figure ) was proven to be a diastereomeric mixture of the (2 S ,4 R )- and the (2 S ,4 S )-isomer with 17% diastereomeric excess in favor of the (2 S ,4 R )-isomer (Figure ). , Hypoglycine B was shown to be the γ- l -glutamyl dipeptide 437 (Figure ). ,, 10 Hypoglycine A and B. 77 Syntheses of Racemic Hypoglycine A 282,285-287 …”
“…Of these, A was crystalline and both seemed to be peptides. Later work suggests that B is a glutamyl derivative of A, which is a free amino acid of novel cyclic structure Holt, Leppla, Kroner & Holt, 1956;Wilkinson, 1958). Bieber & Clagett (1956) isolated from young wheat plants, as the N-2:4-dinitrophenyl derivative, what appeared to be a hexapeptide having aspartylthreonyl as its N-terminal sequence.…”
3214. Use of the inhibitors fluorocitrate and parapyruvate shows that the interconversion of substrates before the formation of 8-aminolaevulic acid is consistent with an active tricarboxylic acid cycle.5. Succinate inhibits the synthesis of 8-aminolaevulic acid by suppressing the formation of succinyl-coenzyme A from citrate, i8ocitrate or ooxoglutarate after itself being first converted into fumarate, malate or oxaloacetate. The inhibition is reversed by increasing concentrations of citrate or wocitrate, but is potentiated by a-oxoglutarate.6. a-Oxoglutarate added exogenously inhibits the condensation of glycine and succinyl-coenzyme A in the formation of 8-aminolaevulic acid. 7. 5:6-Dimethylbenzimidazole also inhibits the condensation of glycine and succinyl-coenzyme A. The inhibition here is partly relieved by increasing concentrations of glycine, but not by increasing concentrations of pyridoxal 5'-phosphate.Protein-free diffusates from ryegraes were studied by Synge (1951), who showed that, whilst the greater part of the nitrogen is present as free amino acids, a substantial proportion (usually about 5 % of the nitrogen of the diffusates) could be segregated in the form of chemically bound amino acids which could be set free by acid hydrolysis. These fractions of diffusate, obtained by electrical transport in a diaphragm cell, contained also much carbohydrate; their nitrogen content was not usually much more than 01I % on dry matter. In the present paper we describe subsequent experiments aimed at characterizing more closely the forms in which bound amino acids occur in diffusates from grass. We have worked chiefly with Italian ryegrass (Lolium multiflorum Lam.), but have not found any essential differences from results previously obtained with perennial ryegrass (L. perenne L.). A few isolated experiments with diffusates from such diverse leaves as those of clover, raspberry, nettle, cabbage and potato showed that by the diaphragm-cell procedure
“…Some in vestigators have reported this form active (11) while others report it inactive with pyruvic oxidase and carboxylase (12,13).. While the disulfide may exist in nature (14, 15), its enzymatic activity most likely is due to prior reduction to the thiol form (16).…”
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