Paulo R. de Oliveira

Composition of leaf and rhizome essential oils of Hedychium coronarium Koen. from Brazil.

Abstract Hydrodistillation of fresh leaves and rhizomes of Hedychium coronarium collected in the Atlantic rain forest of southeastern Brazil afforded essential oils in 0.68% and 0.20% yields, respectively. Analysis of the oils by GC and GC/MS revealed as predominant constituents in the leaf oil β-caryophyllene (43.0%), caryophyllene oxide (12.1%) and β-pinene (11.6%,), whereas 1,8-cineole (34.8%), β-pinene (16.7%) and α-terpineol (13.1%) were the major components identified in the rhizome oil.

Influence of OH⋯N and NH⋯O inter- and intramolecular hydrogen bonds in the conformational equilibrium of some 1,3-disubstituted cyclohexanes through NMR spectroscopy and theoretical calculations.

The analysis of concentration effects in the (1)H NMR data of cis-3-aminocyclohexanol (ACOL) showed that its diequatorial conformer changes from 60% at 0.01 mol L(-1) to 70% at 0.40 mol L(-1) in acetone-d(6). A similar increase was also observed for the diequatorial conformer of cis-3-N-methylaminocyclohexanol (MCOL), from 32% (CDCl(3) 0.01 mol L(-1)) to 55% (CDCl(3) 0.40 mol L(-1)). The increase in solvent basicity leads to a large stabilization effect for the diequatorial conformer of both compounds too. For ACOL, it changes from 47% (ΔG(eqeq-axax)=0.06 kcal mol(-1)) in CCl(4) to 93% (ΔG(eqeq-axax)=-1.53 kcal mol(-1)) in DMSO, while for MCOL it goes from 7% (ΔG(eqeq-axax)=1.54 kcal mol(-1)) in CCl(4) to 82% (ΔG(eqeq-axax)=-0.88 kcal mol(-1)) in pyridine-d(6). These results indicate that the intramolecular hydrogen bonds (IAHB) OH⋯N and NH⋯O stabilize the diaxial conformers of these compounds in a non-polar solvent. For cis-3-amino-1-methoxycyclohexane (ACNE) and cis-3-N-methylamino-1-methoxy-cyclohexane (MCNE) no changes were observed in equilibrium with the variation of solvent polarity. These results indicate for the first time that the IAHB NH⋯O is not strong enough to stabilize the diaxial conformer of these compounds and that the conformation equilibria of the cis isomers of compounds ACOL and MCOL are influenced only by the IAHB OH⋯N. Moreover, the presence of a secondary amino group (93% of diaxial conformer in CCl(4)) leads to an IAHB OH⋯N stronger than in primary and tertiary amino-derivatives (53 and 54% of diaxial conformer, respectively) for 1,3-disubstituted cyclohexanes. Values obtained from the theoretical data through the B3LYP functional are in agreement with the experimental results and indicate that the IAHB strength that influences the conformational equilibrium of these compounds is the IAHB OH⋯N. Thus, the IAHB NH⋯O do not stabilize the diaxial conformer of the cis isomer of compounds ACNE and MCNE showing that the diequatorial conformer will always be more stable than the diaxial conformer, independent of concentration or solvent.

Seasonal Variation of the Volatile Constituents from Leaves of Pimenta pseudocaryophyllus (Gomes)

Abstract The chemical variation of volatile constituents from leaves of Pimenta pseudocaryophyllus collected bimonthly for one year from a locality in the Atlantic Rain Forest, southeastern Brazil, was determined by GC/MS. Seven com- pounds were identified and characterized, revealing a predominance of phenylpropanoids (15.4–70.9%) and variable amounts of monoterpenes (0.5–5.3%). The composition of the oil changed month by month. The best yield of oil was obtained in November, and the major component chavibetol was present in all samples (50.2–70.9%). The chavibetol content showed significant seasonal variation, with the maximum percentages of 69.1% and 70.9% measured in January and November, respectively

Leaf Essential Oil Compositon of Pimenta pseudocaryophyllus (Gomes) L. R. Landrum Native From Brazil

Abstract Hydrodistillation of fresh leaves of Pimenta pseudocaryophyllus Gomes collected in the Atlantic Forest, south-eastern Brazil, afforded the essential oil in 0.48% yield. The major component was isolated from oil and analyzed by GC, GC/MS and NMR techniques, which revealed the compound chavibetol (70.9%). Others major constituents found were methyl eugenol (20.7%) and o-cymene (2.8%).

Total synthesis of targretin via palladium catalyzed crosscoupling reaction of a vinyl organozinc intermediate

In the last two decades, retinoids as isotretinoin, etretinate and acitretin have been utilized in treatment of primary cutaneous T-cell lymphoma (CLTC) showing modest response in rats. 1 However, the bexarotene (targretin®) 1 emerged as a potent and highly selective ligand for the retinoid X receptors (RXRs) applied in human patients to combat the CLTC, which have become a serious public health problem.