RESUMO
A short and highly efficient synthesis of (+)-biotin in 10 steps with 20% overall yield has been achieved from L-cysteine involving amidoalkylation of hydroxy imidazothiazolone 4 via an acyliminium ion intermediate to furnish C-7-substituted imidazothiazolones 5b as the key step.
Assuntos
Biotina/síntese química , Imidazóis/síntese química , Tiazóis/síntese química , Alquilação , Conformação Molecular , EstereoisomerismoRESUMO
We screened 125 Pseudomonas strains from our culture collection for the production of hydantoinase activity using DL-phenylhydantoin as a substrate. Pseudomonas desmolyticum NCIM 2112 was found to be the best hydantoinase (dihydropyrimidinase E.C. 3.5.2.2) producer. The enzymatic reactions were carried out using 18-20-h grown cells in nutrient broth and 5-phenylhydantoin as the substrate. Optimization studies for the biotransformation reaction were performed to increase product yield. The optimum pH and temperature for D(-)N-carbamoylphenylglycine production were 9.5 and 30 degrees C, respectively. Biotransformation under these alkaline conditions allowed the complete conversion of 27.0 g l-1 of DL-phenylhydantoin to 26.5 g l-1 of N-carbamoylphenylglycine within 24 h, with a molar yield of 90%. The hydantoinase involved in this biotransformation process was strictly D-stereospecific, because the product isolated was pure D(-)N-carbamoylphenylglycine. This pure product was further chemically converted to D(-)phenylglycine using nitrous acid with an 80% chemical yield. Thus, the overall conversion efficiency of DL-5-phenylhydantoin to D(-)phenylglycine was found to be 65-68%.
Assuntos
Amidoidrolases/metabolismo , Dipeptídeos/síntese química , Glicina/análogos & derivados , Estereoisomerismo , Bicarbonatos/farmacologia , Biotransformação/genética , Boratos/farmacologia , Dipeptídeos/isolamento & purificação , Glicina/isolamento & purificação , Hidantoínas/metabolismo , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Estrutura Molecular , Ácido Nitroso/metabolismo , Fenilacetatos/isolamento & purificação , Fenilacetatos/metabolismo , Pseudomonas/enzimologia , Temperatura , Ureia/análogos & derivados , Ureia/isolamento & purificação , Ureia/metabolismoRESUMO
A poly(vinyl chloride) matrix membrane ion-selective electrode for the determination of the denatonium ion based on the denatonium salt of tetraphenylborate is described. The response characteristics of the electrode for the denatonium ion and for several quaternary ammonium compounds were studied. The potentiometric determination of denatonium benzoate in rapeseed oil in the range 1-10 ppm agreed to within +/-5% of the spiked amounts. The application of the electrode to the titrimetric determination of several quaternary ammonium compounds using sodium tetraphenylborate as the titrant is also described.
