39139-90-7Relevant academic research and scientific papers
Novel anti-tuberculosis agents from MCR libraries
Doemling, Alexander,Achatz, Sepp,Beck, Barbara
, p. 5483 - 5486 (2008/02/12)
Structure-based design of libraries of multi-component reaction products yields novel potent anti-tuberculosis compounds. Synthesis and preliminary biological results are presented.
Factors Controlling Regioselectivity in Deprotonations of Unsymmetrical Ketimines
Smith, J. Kirk,Bergbreiter, David E.,Newcomb, Martin
, p. 4396 - 4400 (2007/10/02)
The regioselectivity of deprotonation of equilibrium E-Z mixtures of the benzyl, n-butyl, cyclohexyl, phenyl, and tert-butyl imines of 2-butanone by lithium diisopropylamide (LDA) in tetrahydrofuran has been shown to be a function of both the nitrogen substituent and the temperature of the deprotonation reaction.High regioselectivity at either the methyl or methylene substituent could be obtained for all imines except the benzyl and n-butyl imines.Pure (Z)-2-butanone imines (R = n-C4H9, c-C6H11, t-C4H9), prepared by LDA deprotonation of acetone imines followed by methylation, were deprotonated by LDA at the methyl position at -78 deg C and at 0 deg C.Studies of the rates of deprotonation of the E and Z isomers of n-butyl, cyclohexyl, and tert-butyl imines of 2-butanone and of the rates and mechanisms of isomerizations of these isomeric ketimines were performed.Temperature dependent deprotonation regioselectivity was also observed in lithium diethylamide deprotonations of the benzyl, cyclohexyl, phenyl, and tert-butyl imines of 2-butanone.A general scheme accounting for these results and other accounts of variable regioselectivity in ketimine deprotonation is presented.
Synthese totale et stereoselective de la dimethyl-6,10 methylidene-9 undecene-5(E) one-2, un des constituants de l'huile de >
Morizur, Jean-Pierre,Tortajada, Jeanine
, p. 175 - 179 (2007/10/02)
(E)-6,10-dimethyl-9-methylidene-undec-5-en-2-one (1) has been recently isolated from the ionone fraction of the > oil (Saussurea lappa Clarke).We describe here the first stereoselective synthesis of this compound.The approach used is based upon Norrish type I reaction of methyl 1-methyl-2-oxocyclopentanecarboxylate (2) (α-methyl-Dieckmann ester) which gives, when irradiated by U.V. light, methyl 5-formyl-2-methyl-2-pentenecarboxylates (3E+3Z) as a mixture of E and Z isomers (80percent yield).These two aldehydes (3) are used as starting material for the total synthesis of ketone 1.Reaction of aldehyde 3E with methylmagnesium iodide (at -25 deg C) gives methyl 6-hydroxy-2-methyl-2-heptenecarboxylate (4E).Modified Collins oxidation of 4E yields methyl 2-methyl-6-oxo-2-heptenecarboxylate (5E), the ketone function being protected by conversion to the corresponding methyl 6,6-(ethylenedioxy)-2-methyl-2-heptenecarboxylate (6E).This α,β-unsaturated ester 6E was selectively reduced by diisobutylaluminium hydryde (Dibal-H) to give 6,6-(ethylenedioxy)-2-methyl-2-heptenol (7E) (in 30percent overall yield from 2).Conversion of 3Z to the allylic alcohol 7Z (with an identical sequence of reactions) was performed in 13percent overall yield from α-methyl-Dieckmann ester 2.Complete Z-E isomerisation of alcohol 7Z was realised in two steps: Collins oxydation led to the corresponding 6,6-(ethylenedioxy)-2-methyl-2-heptenal (8Z) which was isomerised slowly at room temperature (or immediately in diluted acidic medium); then selective reduction by DibalH gave the allylic alcohol 7E.Alcohol 7E was easily transformed into 2-chloromethyl-6,6-(ethylenedioxy)-2-heptene (9E) via the intermediate tosylate by LiCl (in HMPT/Et2O).Completion of the synthesis required the introduction of a six-carbon unsaturated unit.This was performed in two steps.In the first one, 10,10-(ethylenedioxy)-2,6-dimethyl-6-undecen-3-one (13E) was obtained by alkylation of isopropylmethylketone by allylic chloride 9E according to the imine procedure by Stork.In the second step, Wittig reaction of 13E with methyltriphenylphosphonium bromide in dimethyl sulfoxide afforded 10,10-(ethylenedioxy)-2,6-dimethyl-3-methylidene-6-undecene (14E)which was deketalised to lead to ketone 1 with a 22percent overall yield from the α-methyl-Dieckmann ester 2.
