Separation and structure determination of nicardipine photoproducts by LC-ESI-MS

A sample of 0.104 m nicardipine in methanol was photoirradiated with a Philips 400 W UV lamp for 3 h in a photochemical chamber. A total of four major photoproducts were found from the HPLC chromatogram. The same sample was used for taking LC-MS, while eight major photoproducts were observed and the structures elucidated by analyzing the CID patterns of their respective mass spectra. A reaction scheme of nicardipine is proposed that the photochemical reactions occur mainly via oxidation of 1,4-dihydropyridine moiety, following the stepwise photo-reduction of the m-nitro group and demethylation of the ester group at 5-position of the pyridine ring. Copyright (c) 2008 John Wiley & Sons, Ltd.     

A new synthesis of 5,7-dicarboxy-2,1-benzisoxazolin-3-one

Condensation of methyl 2-isoxazolin-5-on-3-yl acetate ( 3 ) and 3-(N,N-dimethylamino)-2-ethoxycarbonylacrolein ( 6 ) gave 5-ethoxycarbonyl-7-methoxycarbonyl-2,1-benzisoxazolin-3-one ( 7a ). Simple hydrolysis of the diester 7a afforded 5,7-dicarboxy-2,1-benzisoxazolin-3-one ( 7b ).     

Photodegradation of a 1,3,4-thiadiazole-urea herbicide. Isolation,characterization, X-ray crystal structure and synthesis of photoproducts

The photodegradation of 1,3-dimethyl-1-(2-(3-fluorobenzylthio)-1,3,4-thiadiazol-5-yl)urea as a thin film and in solution is described. The two photoproducts from thin-film photolysis were characterized by spectral and synthetic methods. The X-ray crystal structure of one of the photoproducts is also reported. The rearrangements were shown to involve an S-to-N benzyl migration, followed by a sulfur-oxygen substitution.     

Synthesis,x-ray structure and molecular mechanics studies of the boar taint steroid (5α -androst-16-en-3-one)

5α-Androst-16-en-3-one has been prepared from 5α-androstan-3β-ol-17-one in an overall yield of 34% by the vinyl iodide route. Accurate molecular dimensions have been determined by X-ray crystal structure analysis and by molecular mechanics calculations. There is significant twisting of the angular methyl groups in the molecule.     

A facile and efficient approach for the synthesis of 3-arylthiazol-2(3H)-one

A facile and efficient method for synthesis of 3-arylthiazol-2(3H)-one through the reaction of acyl azide and 1,4-dithiane-2,5-diol was reported. This reaction proceeded at 80?°C at first and then in acidic condition at room temperature, to afford products in good yields for a wide range of substrates and a possible mechanism has also been proposed.     

Domain structure of organic crystals. Crystal structure of 3-bromobicyclo[3. 3. 1]non-2-en-4-one

M. V. Lomonosov Moscow State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 6, pp. 104–107, November–December, 1990.     

The structure characteristics of photoproducts of indolinospirooxazines

Photochromic reactions of four indolinospirooxazine derivatives have been studied using nanosecond laser flash photolysis techniques. Photolysis of the four compounds in acetonitrile and in cyclohexane all leads to the formation of the short-lived CT intermediates as the predominant photoproducts. In certain circumstances few photomerocyanines (PMC) can be observed. From the absorption bands and the lifetimes of CT intermediates, it has been speculated that the substituents at the nitrogen atom of the indole ring influence the structural characteristics of CT intermediates mainly through steric hindrance effects, whereas the substituents at the 5 position of the indoline ring influence mainly through electron effects. A potential energy surface model is established to explain the results.     

A simple and efficient one-step synthesis of 3-substituted-4-hydroxyquinolin-2-one derivatives

A new simple and efficient one-step procedure for the preparation of 3-substituted-4-hydroxyquinolin-2-one derivatives was developed. Product isolation is simple, isolated yields are good to excellent and this method tolerates a variety of substitution patterns.     

Chemical synthesis and structure determination of venom toxins

Venom toxins are receiving growing interests as novel therapeutics and biophysical probes. This review briefly discusses recent advances in the chemical synthesis and structure determination of venom toxins.     

Three-component synthesis of tricyclic lactams containing the pyrrolizidin-3-one moiety

Tricyclic lactams containing the pyrrolizidin-3-one moiety were synthesized by the three-component reaction of aromatic aldehydes, glutamic acid (or glutamine), and N-methylmaleimide. The cascade reactions involve the stereospecific generation of azomethine ylides, the 1,3-dipolar endo- and exo-cycloaddition of a dipolarophile to the ylides, and the lactamization and afford two series of stereoisomeric pyrrolizidin-3-ones. The alkaline hydrolysis of the products of the mulitcomponent reaction gives oxopyrrolizidinedicarboxylic acid derivatives.     

A novel highly stereoselective synthesis of 2,3-disubstituted 3H-quinazoline-4-one derivatives

[structure: see text]. An efficient three-step synthesis of chiral 3H-quinazoline-4-one derivatives from commercial materials is disclosed. The Mumm reaction of imidoyl chloride with alpha-amino acids followed by reductive cyclization affords enantiomerically pure (ee >93%) quinazoline-4-ones in good overall yield. A comparison with existing approaches indicates that this method is superior for hindered substrates.     

Carotenoid synthesis with 4-(t-butylthio)-3-buten-2-one. A new synthesis of isorenieratene

Isorenieratene has been efficiently synthesized using 4-(t-butylthio)-3-buten-2-one as chain lengthening agent.