An Easy Route to Enantiomerically Enriched 7- and 8-Hydroxystearic Acids by Olefin Metathesis - Based Approach

The synthesis of enantiomerically enriched 7- and 8-hydroxystearic acids (7- and 8-HSA) has been successfully accomplished starting from chiral non racemic 1-pentadecen-4-ol and 1-tetradecen-4-ol respectively. Their Yamaguchi\u2019s esterification with 4-pentenoic and 5-hexenoic acids respectively afforded the suitable dienic esters which were submitted to ring closing metathesis reaction. After hydrogenation and basic hydrolysis of the complex reaction mixture, chiral non racemic 7- and 8-HSA were obtained in about 40% total yield

NMR quantification of 16-O-methylcafestol and kahweol in Coffea canephora var. robusta beans from different geographical origins

Diterpenes have recently received a great deal of interest as tools to investigate the botanical origin of coffee. Specifically, kahweol has been proposed as a marker of Coffea arabica while 16-O-methylcafestol (16-OMC) is a Coffea canephora specific marker and its detection and quantification allow the authenticity of pure C. arabica roasted coffee blends to be assessed. In this study, we evaluated the possibility of the industrial use of the quantification of these diterpenes to assess the relative amounts of the two coffee species in blends. The content of 16-OMC and kahweol was determined in 78 samples (i.e., 39 green and the corresponding 39 roasted beans) of C. canephora from different geographical origins using a recently published NMR approach. Our results show a small natural variability in 16-OMC content for the Asian samples (average content = 1837 \ub1 113 mg/kg) while a much larger spread was found for the African samples (average content = 1744 \ub1 322 mg/kg). This large variability prevents the use of 16-OMC to quantify C. canephora in unknown roasted coffee blends. We also show that kahweol cannot be considered a specific C. arabica marker since it was detected almost all coffees and quantified in about 30% of the C. canephora samples

Synthesis of p-coumaroylquinic acids and analysis of their interconversion

The synthesis of four isomers of p-coumaroylquinic acids was performed by esterification of p-acetylcoumaroylchloride with a suitably protected (-)-quinic acid. All isomers have been characterized by means of NMR spectroscopy and circular dichroism. Acyl migration was observed in the synthesis of 3-0-p-coumaroylquinic acid and 4-O-p-coumaroylquinic acid. Calculations on the most stable conformations of all isomers have also been performed to explain the acyl migration observed during the synthesis procedure

Hydroxycinnamoyl amino acids conjugates: A chiral pool to distinguish commercially exploited Coffea spp

The synthesis of five hydroxycinnamoyl amides (HCAs) was accomplished and their identification and quantification in the green coffee bean samples of Coffea arabica, Coffea canephora, and Coffea liberica was performed. The HCAs p-coumaroyl-N-tyrosine 1b, caffeoyl-N-phenylalanine 2b, caffeoyl-N-tyrosine 3b, and p-coumaroyl-N-tryptophan 4b were characteristic of the C. canephora species while caffeoyl-N-tryptophan 5b was present in both C. canephora and C. arabica, but with higher content in C. canephora. The HCAs presence was also analyzed in C. liberica for the first time and none of the targeted compounds was found, indicating that this species is very similar to C. arabica species. Between C. canephora samples from various origins, significant differences were observed regarding the presence of all the HCAs, with C. canephora from Tanzania containing all five derivatives

Bicyclic g-butyrolactones. Relation between conformation of the lactone ring and chiroptical properties

The CD curves of a set of condensed gamma-butyrolactones have been investigated. A simple correlation between the sign of the Cotton effect (CE) and the configuration of C-alpha can be deduced from the resulting data

Recent Aspects of the Synthesis of Enantiopure 5-oxo-tetrahydro-3-furan carboxylic acids

Recent advances in enantioselective synthesis of 5-oxo-tetrahydro-3-furancarboxylic acids are surveye

Synthesis of optically active condensed gamma-lactones from 2-(2-nitroethyl)cyclohexanols. Part II

Baker's yeast shows chemo-, diastereo- and enantioselectivity in the reduction of mixtures of 2-nitroalkylated cyclohexanones. The resulting optically active, nitro-substituted alcohols can be easily transformed into condensed gamma-lactones. In that way (+)-isomintlactone, 5, in admixture with its constitutional isomer (-)-6 can be obtained

Baker's Yeast reduction of 4-hetero-2-(2-nitroethyl)cyclohexanones

Baker's yeast reduction of 3-(2-nitroethyl)-tetrahydro-4H-pyran-4-one 10 and 3-(2-nitroethyl)-tetrahydro-4H-thiopyran-4-one 11 gave the corresponding optically active cis alcohols with good diastereo- and enantioselectivity. The unreacted optically active ketones were also isolated

Kinetic Enzymatic Resolution of Alkyl tetrahydro-4-methylene-2-alkyl-5-oxo-3-furancarboxylates

Tetrahydro-4-methylene-2-alkyl-5-oxo-3-furancarboxylic acids belong to the class of paraconic acids which are characterized by the gamma-lactone moiety, an alkyl chain at C-2, a carboxylic group at C-3, and a methyl or a methylene group at C-4.1) Paraconic acids having a methylene group at C-4 are in general biologically active natural compounds. A few of them are listed in Figure 1.The methyl and ethyl esters of methylenolactocin 2 and C75 3 were synthesized in racemic form following the procedure reported by Carlson and Oyler 2) and they were resolved by enzymatic hydrolysis. (\u2013)-Methylenolactocin was obtained with 80% e.e. using alfa-chymotrypsin (alfa-CT) while (+)-methylenolactocin and (+)-C75 were obtained with 76% e.e. and 96% e.e. 3) respectively, using Acylase I. References: 1) Bandichhor, R.; Nosse, B.; Reiser, O. Top. Curr. Chem. 2005, 243, 43\u201372. 2) Carlson, R.; Oyler, A. J. Org. Chem. 1976, 41, 4065\u20134069. 3) Chakrabarty, K.; Forzato C.; Nitti, P.; Pitacco G.; Valentin, E. Letters in Organic Chemistry 2010, 7, 245-248