José Eduardo Damas Martins

Evaluation of lipase from Candida rugosa in the resolution of endo-(±)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.13,6.02,7.05,9]dodecan-4-alcohol

Abstract endo -(±)-1,8,9,10,11,11-Hexachloropentacyclo[6.2.1.1 3,6 .0 2,7 .0 5,9 ]dodecan-4-ol (±)- 7 and exo -(±)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.1 3,6 .0 2,7 .0 5,9 ]dodecan-4-ol (±)- 4 have been prepared and the enantiomeric enrichment capacity of the lipase from Candida rugosa in the transesterification with vinyl acetate of these compounds was evaluated. It was verified that the lipase recognize only the alcohol (±)- 7 , producing endo -(+)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.1 3,6 .0 2,7 .0 5,9 ]dodecan-4-yl acetate (+)- 8 with ee >95% and conversion of 44% as the only product.

Study of the kinetic resolution of (′)-10-exo-hydroxy-pentacyclo[6.2.1.13,6.02,7.05,9]dodeca-4-one by lipase catalysis and the intramolecular racemization of the pure enantiomer by thermal dyotropic reaction

Abstract In this work, the modified synthesis of (±)-10- exo -hydroxy-pentacyclo[6.2.1.1 3,6 .0 2,7 .0 5,9 ]dodeca-4-one (±)- 10 as well as its resolution by lipase-catalyzed transesterification with vinyl acetate is described. A thermal racemization process of (+)- 10 to (±)- 10 was observed. A mechanism involving racemization of (+)- 10 through dyotropic intramolecular hydrogen migration is proposed and supported by computational analysis.

New Efficient Route to the Synthesis of Enantiopure (+) and (−) Bicyclo[2.2.1]heptan‐syn‐2,7‐diol using Lipase‐Catalyzed Transesterifications

Abstract Starting from racemic 7,7‐dimethoxy‐1,4,5,6‐tetrachlorobicyclo[2.2.1]hept‐5‐en‐2‐endo‐ol (±)‐7, using lipase‐catalyzed transesterification and a series of standard procedures, we prepared the enantiomers (+)‐(2R, 7S) and (−)‐(2S, 7R) bicyclo[2.2.1] heptan‐2,7‐syn‐diol 3 through a new alternative route with excellent yields and enantiomeric excess (up to 99%). These chiral bidentate compounds possess very rigid molecular structures and a favorable stereochemistry for metal coordination, thus becoming promising chiral ligands for asymmetric synthesis.

On the mechanism of skeletal rearrangements in the acid catalysed acetylation of isodrin

1,8,9,10,11,11-Hexachlorotetracyclo[6.2.1.13,6.02,7]dodec-9-en-4-exo-yl acetate, tetracyclic1; 1,2,2,3,10,11-hexachloropentacyclo[5.4.1.03,10.04,12.05,9]dodecan-8-exo-yl acetate, half-cage2; 1,2,2,3,10,11-hexachloropentacyclo[5.4.1.03,10.04,12.05,9]dodecan-8-endo-yl acetate, half-cage3 and 1,9,10,11,11,12-hexachlorohexacyclo[5.4.1.02,6.03,10.04,8.09,12]dodecane, birdcage4 were obtained from acid catalysed acetylation of isodrin. It was observed that the intramolecular rearrangement control is highly dependent on reaction time. The equilibria involved in these rearrangements were determined by gas chromatography. Semiempirical calculations at the PM3-MNDO, AM1 and MNDO levels have been performed to obtain the optimized geometry of the reagent, products, intermediates and transition states for the rearrangement mechanism. The results of the calculations are in good agreement with the experimental data. On the basis of the theoretical and experimental investigations we propose a revised mechanism which involves a new transition state and a new non-classical reaction intermediate.