Microbial decyanation of 1-benzylpyrrolidine-2,5-dicarbonitrile. Mechanistic investigations
Various bacterial and fungal strains were screened for their ability to catalyse the regioselective hydrolysis of 1-benzylpyrrolidine-2,5-dicarbonitrile (1). Among the examined strains, Rhodococcus opacus sp-lma whole cells transformed both isomers of 1 into 1-benzyl-5-cyano-2-pyrrolidinone (2) and N-benzylacetamide (3). These reactions are difficult to achieve chemically and the synthesis of compound 2 did not compete with microbiological catalysis in terms of efficiency and respect for the guidelines of green chemistry. To distinguish between an oxidative or hydrolytic based-mechanism, the origin of the oxygen atom in 2 was investigated by using 18O2 and 18OH2 coupled with GC-MS analysis. These experiments confirmed that the oxygen atom in 2 came from water and not from molecular oxygen. The reaction is probably initiated by the dehydrogenation of 1 to generate the iminium ion, which could be trapped by a water molecule to form the cyanohydrin. The cyanohydrin intermediate would spontaneously break down to the γ-lactam product 2. Conversion of 1 to 2 by induced rat liver microsomes suggests the involvement of a Cyt P-450-type enzyme. A mechanism that accounts for the formation of 3 is also proposed.
Substitution reactions of 2-phenylsulphonyl-piperidines and -pyrrolidines with carbon nucleophiles: Synthesis of the pyrrolidine alkaloids norruspoline and ruspolinone
Several 2-phenylsulphonyl-piperidines and -pyrrolidines were prepared from the corresponding N-acyl aminals by treatment with benzenesulphinic acid. On reaction with various carbon nucleophiles these sulphones gave good yields of substitution products. Typical nucleophiles used in these studies were organometallic reagents derived from Grignard reagents and zinc halide together with silyl enol ethers, silyl ketene acetals, allylsilanes and trimethylsilyl cyanide in the presence of a Lewis acid. These methods were employed in the synthesis of two natural product alkaloids; Norruspoline (38) and Ruspolinone (40).
Brown, Dearg S.,Charreau, Philippe,Hansson, Thomas,Ley, Steven V.
p. 1311 - 1328
(2007/10/02)
Carbon-carbon bond forming reactions of ω-oxylactams in acid and neutral medium
1,3-Dicarbonyl compounds and hydroxybenzenes condense under the influence of acid with ω-hydroxylactams 1-7 in an intermolecular process, thereby affording ω-alkylated lactams 8-13.The reactive intermediate in the carbon-carbon bond forming step is a cyclic N-acyliminium ion.The intramolecular variant affords keto ester 19.Upon activation of the ω-hydroxylactam as a hexafluoroisopropoxy ester, condensations with cyanide in aprotic polar solvents under neutral conditions become possible.
Speckamp, W. N.,Boer, J. J. J. de
p. 405 - 409
(2007/10/02)
Trapping of Metabolically Generated Electrophilic Species with Cyanide Ion: Metabolism of 1-Benzylpyrrolidine
Incubations of 1-benzylpyrrolidine (4) and specifically deuterium-labeled analogues of 4 with rabbit liver microsomal preparations in the presence of cyanide ion have led to the characterization of 1-benzyl-2-cyanopyrrolidine (13), cis- and trans-1-benzyl
Ho, Bert,Castagnoli, Neal
p. 133 - 139
(2007/10/02)
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