- Enzymatic optical resolution of norbornanecarboxylic esters using Pig Liver Esterase
-
The hydrolysis of a series of norbornane-type carboxylic esters catalyzed by pig liver esterase (PLE) has been investigated.It was found that an exo-ester function (syn to the C7 methylene group) is hydrolyzed with high preference.Enantioselective hydrolysis can be accomplished when a vicinal carbonyl-containing function (ester, formyl, acetyl) is present in a trans position with respect to the exo ester.The regiospecifity of the enzymatic hydrolysis has been used for the separation of exo/endo mixtures of the cycloadducts derived from cyclopentadiene and alkene esters.The regiospecifity and enantioselectivity of the enzymatic hydrolysis of norbornane-type esters were analyzed in terms of Tamm's substrate model and also by Griengl's method.
- Gastel, F. J. C. van,Klunder, A. J. H.,Zwanenburg, B.
-
p. 175 - 184
(2007/10/02)
-
- Deuterium Kinetic Isotope Effects in the 1,4-Dimethylenecyclohexane Boat Cope Rearrangement
-
In order to examine the extent of bond making in the boat-like 3,3-sigmatropic shift transition states, trans-2,3-dimethyl-1,4-dimethylenecyclohexane (T) and its exomethylene tetradeuteria derivative (TXD) were prepared.The 3,3-shift of TXD at 305 deg C r
- Gajewski, Joseph J.,Jimenez, Jose Leonardo
-
p. 468 - 474
(2007/10/02)
-
- Derivatives of Bicyclooctane-2,6:3,5-dicarbolactone
-
The reactions of the title dilactone with both acid and base are discussed.Evidence is presented for stable γ-lactones in the bicyclooctane-2,6-carbolactone series.Epimerization α to hindered acid groups occurs under acetylating conditions to relieve steric strain in this system.
- Carman, Raymond M.,Smith, Stephanie S.
-
p. 1285 - 1294
(2007/10/02)
-
- Additions of Group 6A and 7A Electrophilic Reagents to Dimethyl endo,endo-Bicyclooct-5-ene-2,3-dicarboxylate: Competitive Formation of γ- and δ-Lactones
-
The reaction of dimethyl endo,endo-bicyclooct-5-ene-2,3-dicarboxylate with chlorine, bromine, iodine, benzeneselenenyl chloride, and benzenesulphenyl chloride has been studied.Under conditions of kinetic control both γ- and δ-lactones are formed, the δ lactone being predominant except in the case of bromine.The thermodynamic product distributions favored the δ-lactone exclusively.A general mechanistic scheme is proposed.
- Garratt, Dennis G.,Ryan, M. Dominic,Beaulieu, Pierre L.
-
p. 839 - 845
(2007/10/02)
-
- Electrophilic additions to strained alkenes. II. The reaction of benzeneselenenyl chloride with tricyclo2,5>deca-3,7-diene derivatives
-
The reactions of benzeneselenenyl chloride with three derivatives of tricyclo2,5>deca-3,7-diene have been investigated in four solvent systems: methylene chloride, acetic acid, acetic acid/LiClO4, and methanol.Under conditions of kinetic control only products of exo-anti attack upon the cyclobutene moiety are isolable when the solvent system is methylene chloride or acetic aicd.This observation also holds in acetic acid/LiClO4 except in the case of dimethyl tricyclo2,5>deca-3,7,9-triene-7,8-dicarboxylate where the major product is that of cross-bonding with solvent incorporation.In methanol products of solvent incorporation, transannular cross-bonding and lactonization (where possible) are observed.A general mechanistic scheme is proposed to account for these observations in accord with earlier results for the analogous arenesulphenylations.
- Garratt, Dennis G.,Ryan, Dominic M.,Kabo, Ann
-
p. 2329 - 2339
(2007/10/02)
-