André L.M Porto

Polyisoprenylated benzophenones from Clusia floral resins.

From the floral resins of various Clusia species, seven polyisoprenylated benzophenones were isolated. HPLC allowed their quantification in all resins, revealing a distribution of benzophenone derivatives distinct from each other. In some species the staminal oils were collected and oleic, stearic and palmitic acids were the main constituents.

Two polyisoprenylated benzophenones from the floral resins of three Clusia species

Abstract From the floral resins of Clusia nemorosa male, C. nemorosa hermaphrodite, Clusia rosea female, Clusia grandiflora male, C. grandiflora female, Clusia insignis male (all section Chlamydoclusia ). C. renggerioides male (with pistillodium), C. renggerioides male (without pistillodium), C. renggerioides female (all section Cordylandra ) belonging to the family Clusiaceae, we have isolated two novel polyisoprenylated benzophenones, nemorosone II and 6- epi -nemorosone, and a xanthone. The latter is the first member of this class of compounds ever isolated from the genus Clusia . HPLC allowed the quantification of these and other methylated benzophenones in the methylated resins revealing that indeed these are the major constituents of Clusia floral resins. Oleic, stearic and some unusual long chain esters and acids are the main constituents of the stamen oils.

Aspergillus terreus CCT 3320 immobilized on chrysotile or cellulose/TiO2 for sulfide oxidation

Abstract The increasing interest in applying chiral sulfoxides in asymmetric syntheses requires their preparation on a large scale, which can be obtained by enantioselective enzymatic oxidation of sulfides. We have focused on the preparation of sulfoxides 1 – 6 using Aspergillus terreus CCT 3320 cells to oxidize the precursor sulfides. These biotransformations lead to enantiomeric excesses (ee) better than 95%. In order to improve the biocatalytic process, the cells were immobilized on two supports, chrysotile and on cellulose/TiO 2 . The immobilized cells showed a similar biocatalytic behavior in the conversion rate and in the sulfoxide enantiomeric excess. Scanning electron microscopy (SEM) micrographs show that the cells are intertwined with the fibers of both supports, allowing fast separation from the reaction media and easing the biocatalyst reuse. Supported cells stored for at least 3 months showed no loss of activity.

Microbial reduction of cyclohexanones

A Brazilian strain of the bacteria Serratia rubidaea CCT 5742 quantitatively reduced 4-tert-butylcyclohexanone and 4-methylcyclohexanone to the less thermodynamically stable diastereoisomeric alcohols cis-4-tert-butylcyclohexanol and cis-4-methylcyclohexanol with a diastereoisomeric excesses (de) of 96% and 44%, respectively. 2-Methylcyclohexanone was also totally reduced to the corresponding alcohols affording the trans-(+)-(1S, 2S)-2-methylcyclohexanol with 78% of de and an enantiomeric excess (ee) of 80%. The cis-(+)-(1S, 2R)-2-methylcyclohexanol was obtained in 98% ee.

HR-DOSY and sulfoxide enantiomeric discrimination by cyclodextrin

Racemic and chiral ethyl-phenylsulfoxide (solute) and -cyclodextrin (chiral selector) were used to compare two NMR methodologies to predict RP-HPLC enantiomeric resolution efficiency. One of them based on the classical approach involving apparent binding constants and complexation-induced chemical shifts at saturation and the other based on 13 CN MR signal splittings (solute and chiral selector in stoichiometric ratio) and HR-DOSY of the same solution. We have concluded that the latter methodology is rather efficient and though more elaborate from the NMR point of view, the results are promising and constitute an alternative method to investigate chiral recognition and other supramolecular phenomena.