Search results for "lcsh:Organic chemistry"
showing 10 items of 438 documents
From Overstoichiometric to Substoichiometric Enantioselective Protonation with 2-Sulfinyl Alcohols: A View in Perspective
2005
A general study of the enantioselective protonation of prochiral enolates with 2-sulfinyl alcohols is reported. The modification of reaction conditions to reduce drastically the amount of chiral proton source needed to obtain a good enantiomeric excess is reported. The effects of the different factors controlling the stereoselectivity are clearly established. Different protocols for enolate generation are compared.
Synthesis of alkyl-5,8-dimethyl-6-phenyl-5,6-dihydropyrazolo[3,4-f] [1,2,3,5]tetrazepin-4(3H)-ones of pharmaceutical interest
2006
The multistep synthesis of two pyrazolo[3,4-f][1,2,3,5]tetrazepin-4(3H)-one derivatives, a new class of fused 1,2,3,5-tetrazepinones with potential antiproliferative activity, has been carried out. Owing to the instability of the above compounds, the last step of the synthesis was performed at -5/0 degrees C. The obtained tetrazepinones, when allowed to stand at r.t. for 24 h, afforded quantitatively 1-phenyl-3,6-dimethylpyrazolo [3,4-d][1,2,3] triazole.
Triazolopyridines 23. Synthesis of 5,5'-bi[1,2,3]triazolo[5,1-a]isoquinoline
2003
5,5'-Bi[1,2,3]triazolo[5,1-a]isoquinoline 6 has been synthesised from [1,2,3]triazolo[5,1-a] isoquinoline 5 by four procedures, dimerisation by LDA, Stille and Suzuki self-coupling reactions, and Suzuki cross-coupling reaction. The last is the best. Compound 6 gives 1,1'bi(acetoxymethyl)-3,3'-biisoquinoline 10 by triazolo ring opening by acetic acid.
Synthesis of pyrazolo[4,3-c][1,2,6]benzothiadiazocine, a new ring system as potential COX inhibitor
2012
Derivatives of the new ring system 1,4-dihydropyrazolo[4,3-c][1,2,6] benzothiadiazocin-11(10H)one 5,5-dioxide were synthesized in five or six steps in 57-66% overall yields and tested as COX inhibitors.
Synthesis of substituted isoindolo[2,1-a]quinoxalin-6-yl–amino and 6-imino-5-yl thiourea derivatives
2014
A series of substituted 1-(5-bromopyridin-2-yl)-3-[2-(isoindolo[2,1-a]quinoxalin-6- ylamino)ethyl]thiourea and 1-(5-bromopyridin-2-yl)-3-[2-(6-iminoisoindolo[2,1-a]quinoxalin- 5(6H)-yl)ethyl]thiourea derivatives were prepared in good yields (63-85%) by reaction between the corresponding amino compounds with 5-bromo-2-isothiocyanatopyridine. All thiourea derivatives, tested for inhibition of HIV-1 RT, showed no significant antiviral activity.
Triazolopyridines 22.1 Description of new 7,9-di(2-pyridyl)[1,2,3]triazolo[5',1':6,1]pyrido[3,2-d]pyrimidines
2002
The new heteroaromatic compounds, 7,9-di(2-pyridyl)(1,2,3)triazolo(5',1':6,1)pyrido(3,2-d) pyrimidines 11a-c, were synthesized in two steps from readily available triazolopyridines 1a-c. Regioselective lithiation of 1a-c followed by treatment with 2-cyanopyridine gave a mixture of compounds 5a-c, and 11a-c in moderate to low yields, together with gums. Similar reactions with the triazolopyridine 1d gave as the only identified compound the triazolopyridine derivative 5d.
SYNTHESIS AND PHARMACOLOGICAL EVALUATION OF 7-SUBSTITUTED1-ETHYL-3,4,10-TRIMETHYL-1,10-DIHYDRO-11H-PYRAZOLO(3,4-c)(1,6)BENZODIAZOCIN-11-ONE: A NEW RI…
2004
Derivatives of the title ring system of type 10 were obtained in good yield by fusion of the intermediates 12. Attempt to cyclize the acetylamino derivative 9 under Bischler-Napieralski conditions failed because of the insufficient electronic density in the position 4 of the pyrazole ring created by the adjacent carbonyl moiety. The derivatives of the new ring system, assayed as anxiolytic agents, showed no significant activity.
Synthesis of pyrazole-4-carbohydrazide derivatives of pharmaceutical interest
2003
New 1-phenylor 1-methyl-5-benzamidopyrazole-4-carbohydrazide derivatives were prepared in 70–90% yields from 1-methylor 1-phenyl-6-phenylpyrazolo[3,4-d]1,3-oxazin-4(1H)-one derivatives and hydrazine hydrate. Small quantities of the isomeric 5-aminopyrazole-4-(Nbenzoyl)hydrazides were detected in some reaction mixtures, proving that intramolecular benzoyl migration can take place in the 5-benzamidopyrazole-4-carbohydrazide molecule. The direct formation of pyrazole-4-carbohydrazides from 5-benzamidopyrazole-4-carboxylic acid ethyl esters and hydrazine hydrate was unsuccessful.
Synthetic approaches towards huperzine A and B
2013
Huperzine A and B are potent acetylcholinesterase inhibitors and promising against Alzheimer's disease. Completed and formal total syntheses of these medically relevant alkaloids are presented and discussed.
Kinetics of photochemical isomerization of TFA-Gly-ZΔPhe into TFA-Gly-EΔPhe
2017
The kinetics of photoisomerization of trifluoroacetyl-(Z)-dehydrophenylalanylglycine into trifluoroacetyl-(E)- dehydrophenylalanylglycine was studied in the hope that light-induced reaction could be useful as a means of preparation of the E-dehydropeptides. The obtained results indicate that if this reaction carried out under irradiation with light of wavelength 360 nm it is practically irreversible and gave nearly quantitatively pure Eisomer Significantly, expected cyclic side-products were not observed in the reaction mixture, thus proving the preparative potential of the elaborated procedure.