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α-N-Protected amino acid hydrazides (1) readily reacted with NaBH4 to afford 5-substituted 4,5-dihydro-1,2,4-triazin-3(2H)-one derivatives 2 in good yields. Unfortunately, the reaction caused partial racemization at the α-amino acidic carbon atom of the starting hydrazide. A mechanism, supported by experimental evidence, has been proposed in an attempt to explain this to date unprecedented reaction. The structure of compounds 2 was confirmed by X-ray structural analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

α-Amino acid phenylhydrazides 1 readily react with levulinic acid to produce the imidazolidin-4-one intermediates 4, which undergo a second ring closure to afford the dihydro-1H-pyrrolo[1,2-a]imidazole-2,5-dione derivatives 5. It has been established that the solvent polarity has a great influence on the rate of the second condensation reaction, but not on the first. A mechanism, supported by experimental evidence, has been proposed to explain how the imidazolidin-4-one intermediates 4, obtained as expected as a mixture of two diastereoisomers, give a single isomer for the bicyclic derivatives 5; the absolute stereochemistry of these compounds has been determined by X-ray crystallographic analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The natural α-amino acid phenylhydrazides 1a−d readily react with the aldehydes 2a−d and ketones 2e−h to produce the 3-(phenylamino)imidazolidin-4-one derivatives 4 in good yields. Their structures were confirmed by X-ray structural analysis. Polycyclic systems were obtained from the reaction of L-tryptophan phenylhydrazide (1d) and L-histidine phenylhydrazide (1e) with benzaldehyde (2c), which gave 1,10-diphenyl-2-(phenylamino)-2,9,10a-triazacyclopenta[b]fluoren-3-one (5dc) and 4,6-diphenyl-7-(phenylamino)-3,4,6,7,8a,9-hexahydro-8H-diimidazo[1,5-a:4′,5′-d]pyridin-8-one (5ec), respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Abstract. Analysis of the acid content of coffee extracts has been performed by adaptation of a procedure, recently introduced by our laboratory, to the task of evaluating both the "volatile" and "non volatile" fractions. Besides useful changes in the preparation of the acid pool, diazobutane was used to obtain esters of volatile acids suitable for GC-MS analysis, to minimize losses of material by evaporation. The new procedures have been used to evaluate changes in the acid content of some Italian-style roasted coffee extracts after accelerated ageing (65 °C, 72 h) and in coffee beans after different amounts of roasting. The origin of formation of volatile acidity was also investigated. Electronic supplementary material is available if you access this article at http://dx.doi.org/10.1007/s00216-002-1561-y On that page (frame on the left side) a link takes you directly to the supplementary material.

A convenient laboratory synthesis of pentachlorobenzonitrile is described.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.