73 research outputs found
The Picard Group of the Universal Abelian Variety and the Franchetta Conjecture for Abelian Varieties
No full textWe compute the Picard group of the universal Abelian variety over the moduli stack Ag,n of principally polarized Abelian varieties over C with a symplectic principal level n-structure. We then prove that over C the statement of the Franchetta conjecture holds in a suitable form for Ag,n
NaOH-Catalyzed Thiolysis of alpha,beta-Epoxyketones in Water. A Key Step in the Synthesis of Target Molecules Starting from alpha,beta-Unsaturated Ketones
No full textNaOH (0.02-0.3 molar equiv) is an efficient catalyst for the thiolysis reactions of alpha,beta-epoxy ketones with alkyl and aryl thiols in water. Thiolysis of 3,4-epoxyheptan-2-one (1) with thiols 2a-d has been accomplished in mild conditions (30 °C and pH 6 or 9) with complete C-R-regioselectivity and anti-stereoselectivity, and the corresponding anti-beta-carbonyl-beta-hydroxysulfides 3a-d have been prepared in excellent yields (95-98%). Compounds 3a-d, depending on their nature and pH conditions, have undergone dehydration, C-3 epimerization reaction, and retroaldol condensation.
Dehydration of anti-3a-d has been chemoselectively carried out by in situ acidic treatment at
70 °C, giving stereoselectively the related (Z)-vinyl sulfides 4 in 89-94% overall yields. Under NaOHcatalyzed thiolysis conditions, cyclic alpha,beta-epoxyketones 6-9 have shown C-R attack only and spontaneously dehydrated to furnish the corresponding vinyl sulfides in high yields (90-96%). The reactions of calchone oxide (10) with thiols 2b-d have exclusively resulted in the formation of â-carbonylsulfides 10b-d (82-93% yield), coming from the nucleophilic attack at the R-position and retroaldol condensation. To highlight the synthetic utility of this procedure, one-pot multisteps preparation of vinyl sulfides 7b and 7c, vinyl sulfoxides 12 and 13, and 1,5,6,7-tetrahydro-4H-1,2,3-benzotriazol-4-one (14) starting from 2-cyclohexen-1-one (11) have also been reported
Synthesis and Far-UV Circular Dichroism Spectra Analysed by Coupled Oscillator Calculations of Some New 4-Substituted [2.2]Paracyclophanes
No full text
InCl3-Catalyzed Regio- and Stereoselective Thiolysis of alpha,beta-Epoxycarboxylic Acids in Water
No full textThe thiolysis of alpha,beta-epoxycarboxylic acids 1a-e by thiols 2a,b is more efficient in water than in dichloromethane or SFC. At pH 9.0 phenylthiolate
generally attacks the C-alpha carbon while at pH 4.0, and in the presence of InCl3 (10 mol %), the thiolysis is exclusively C-beta regioselective. In
all cases, the processes are completely anti-diasteroselective, and the corresponding products 3, 4, and 5 have been isolated in good yields.
Both water and catalysts have been recovered and reused
Induction of apoptosis by 1,4-benzothiazine analogs in mouse thymocytes
No full text1,4-Benzothiazine (1,4-B) derivatives exert numerous effects in vivo and in vitro, including neurotoxicity and antitumor cytotoxicity. To analyze the mechanisms responsible for 1,4-B-induced cytotoxicity, we performed experiments to evaluate the possible apoptotic effect. For that purpose, we used mouse thymocytes, a cell population well sensitive to induction of apoptosis that has been used to assay apoptosis in many experimental systems. Results indicate that a number of 1,4-B analogs are able to induce both thymocyte apoptosis in vitro and thymus cell loss in vivo. Moreover, analysis of the structure-activity relationship indicate that the sulfur (S) oxidation state, the presence of the carbonyl group, and the nature and position of the side chain modulate the apoptotic efficacy. Moreover, results of in vitro experiments show that the 1,4-B-induced apoptosis associates with different biochemical events including phosphatidylcholine-specific phospholipase C activation, acidic sphingomyelinase activation and ceramide generation, loss of mitochondrial membrane potential (DeltaPsim) and cytochrome c release, and caspase-8, -9, and -3 activation. These results indicate that 1,4-B analogs induce apoptosis through a complex of biochemical events
3-Nitrocoumarins as Dienophiles in the Diels-Alder Reaction in Water. An Approach to the Synthesis of Nitrotetrahydrobenzo[c]chromenones and Dihydrodibenzo[b,d]furans
No full text
NADPH-diaphorase histochemistry in the rat cerebellar cortex and hippocampus : effect of electrolytic lesions of the nucleus basalis magnocellularis
No full textI.F. 1.89
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