85440-70-6Relevant academic research and scientific papers
Highly enantioselective transformations on 3,4-dihydroxytetrahydrofurans catalyzed by lipases
Recuero, Veronica,Brieva, Rosario,Gotor, Vicente
, p. 1684 - 1688 (2008/12/21)
Enzymatic acylations and alkoxycarbonylations of cis- and trans-3,4-dihydroxytetrahydrofuran and hydrolysis of their diacetylated and dialkoxycarbonylated derivatives have been studied. High enantioselectivity is obtained using Pseudomonas cepacia lipase as a catalyst in the hydrolysis of the trans-diacetyl derivative, while for the desymmetrization of the cis-3,4-dihydroxytetrahydrofuran the best results are obtained in the acylation process catalyzed by Candida antarctica lipase B.
Regio- and Stereochemistry of the Acid Catalyzed and of a Highly Enantioselective Enzymatic Hydrolysis of Some Epoxytetrahydrofurans.
Barili, Pier Luigi,Berti, Giancarlo,Mastrorilli, Ettore
, p. 6263 - 6276 (2007/10/02)
3,4-Epoxytetrahydrofuran is hydrolyzed by rabbit liver microsomal epoxide hydrolase (MEH) with a high preference for the attack by water at the (S) epoxide carbon to give the (R,R)-diol with an e.e. of 96.5 +/- 0.3percent.In the acid catalyzed hydrolysis of trans-3,3a-epoxyoctahydrobenzofuran the oxirane ring is opened with inversion exclusively on the tertiary carbon atom to give the corresponding trans-diol, whereas hydrolysis of the cis isomer is less regioselective, the ratio of attack at the tertiary and secondary carbons being 81:19.The MEH catalyzed hydrolysis of the same two substrates occurs exclusively at their secondary carbons and with a very high enantioselectivity: only enantiomers of configuration (3S,3aR) of the cis- and trans-epoxide are substrates for the enzyme and give the corresponding (3R,3aR)-diols with at least 98percent e.e, the corresponding (3R,3aS)-epoxides being totally resistant to enzymatic hydrolysis.These results agree well with previously formulated rules on steric requirements of MEH substrates.Absolute configurations and optical purities of new chiral compounds were obtained by chiroptical, NMR and chiral chromatographic techniques.Conformations of the octahydrobenzofuran derivatives were derived from coupling constants and found to be in fairly good agreement with those deduced from molecular mechanics calculations.
EQUILIBRATION OF ALDITOL ANHYDRIDES IN ACETIC ACID
Wisniewski, Andrzej,Gajdus, Jerzy,Sokolowski, Janusz,Szafranek, Janusz
, p. 11 - 20 (2007/10/02)
Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4.Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups.Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are also proposed as intermediates in the structural isomerisation.Drastic treatment of each alditol gives equilibrium mixtures.The equilibrium concentrations are used to calculate free-energy differences.
