4317-72-0Relevant academic research and scientific papers
A method for the synthesis of cyclopropanes by regiospecific and regioselective magnesium carbenoid 1, 3-CH insertion as the key reactions
Watanabe, Hiroyuki,Ogata, Shingo,Satoh, Tsuyoshi
experimental part, p. 5675 - 5686 (2010/11/24)
Addition reaction of two geometrical isomers of 1-chlorovinyl p-tolyl sulfoxides derived from unsymmetrical ketones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl acetate gave single diastereomers of the adduct, respectively. Treat
Effect of Distant Groups on the Enantioselectivity in Kinetic Resolution of sec-Alcohols Catalyzed by Microbial Lipases
Ljubovic, Edina,Sunjic, Vitomir
, p. 99 - 117 (2007/10/03)
A short series of racemic phenoxyalkyl-alkycarbinols, possessing perturbing groups at different distances from the stereogenic center, was prepared. The sec-alcohols (±)-1-phenoxy-2-hydroxybutane (6), (±)-1-phenoxy-3-hydroxyhexane (11), (±)-1-phenoxy-4-hydroxyoctane (15) and (±)-1-phenoxy-5-hydroxydecane (19) were prepared. The enantioselectivity of their acetylation by vinylacetate catalyzed by microbial lipases in n-hexane was determined. The products of this acetylation were (±)-1-phenoxy-2-acetoxybutane (7), (±)-1-phenoxy-3-acetoxyhexane (12), (±)-1-phenoxy-4-acetoxyoctane (16), and (±)-1-phenoxy-5-acetoxydecane (20). The efficacy of kinetic resolution, expressed as E-value, generally diminishes with the distance of the perturbing phenoxy (RL) and methyl (RM) groups. Twenty lipases from commercial sources were screened for their enantioselectivity; for two lipases with broadest substrate selectivity, Geotrichum candidum (GCL) and Candida cyclindracea (CCL (S), from Sigma), non-monotonous correlation between E-value and the distance (n) of the perturbing group was observed. With GCL lipase, a remarkable turnover of enantioselectivity from preferred acetylation of (R)-enantiomers in 6, 11, 15 to (S)-enantiomer of 19 was observed, indicating that relative steric requirements of the distant perturbing groups in the latter do not control the enantioselective bias. The herewith reported results are correlated with the previously observed stereoselective acetylation of (S)-sec-alcohols (3S,7S)-trans-3,4,5,6,9,10-octahydro-7,14,16-trihydroxy-3-methyl-1H-2- benzoxacyclotetradecene-1-one (1) and (3S,7S)-3,4,5, 6,9,10,11,12-decahydro-7,14,16-trihydroxy-3-methyl-1H-2-benzoxa- cyclotetradecane-1-one (3), macrocyclic derivatives of resorcyllic acid, and also with the results of MM2 calculations for some low energy conformations.
Correlation between distance of the perturbing groups and enantioselectivity of the lipase catalyzed acetylation of acyclic sec alcohols
Ljubovic, Edina,Sunjic, Vitomir
, p. 1 - 4 (2007/10/03)
Study of kinetic resolutions of racemic sec alcohols 1-4, by acetylation to 5-8 with a series of microbial lipases in n-hexane, revealed the broadest selectivity of Geotrichum candidum (GCL) and Candida cylindracea (CCL(S), from Sigma) lipase in accepting these conformationally flexible substrates. Surprisingly, for both lipases non-monotonous correlation between E-value and the distance (n) of perturbing groups in 1-4 is observed. GCL preferred small and large substrates, whereas CCL preferred medium-size substrates. For GCL lipase a remarkable turnover of enantioselectivity was observed on going from 1-3 to 4, revealing that relative steric requirements of the larger phenoxy groups vs smaller methyl group does not control the enantioselective bias in the latter. For Candida cylindracea (CCL(A), from Amano) lipase the conversion and E vary in a monotonous fashion from smaller to larger substrates.
