RESUMO
A study of Argentinean red wines was performed by direct injection of untreated wine samples into a liquid chromatography-mass spectrometry system, processing the collected data with two chemometric algorithms: multivariate curve resolution with alternating least-squares and discriminant unfolded partial least-squares (D-UPLS). The objectives were: (1) the chemometric resolution of profiles in the modes represented by elution time and m/z ratio, (2) the discrimination of samples according to varietal and/or geographical origin, and (3) the identification of key compounds helping to perform sample discrimination. The results indicate that all wine varietals can be adequately discriminated, and also three wine producing regions (located in the east, south and north of the Cuyo region) were differentiated from the remaining regions. The applied chemometric models allowed the tentative identification of anthocyanin compounds as responsible for both type of discriminations, in the case of D-UPLS by employing the concept of variables importance in the projection.
Assuntos
Antocianinas/análise , Biomarcadores/análise , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Vinho/classificação , Argentina , Análise Discriminante , Análise dos Mínimos Quadrados , Vinho/análiseRESUMO
The Diels-Alder reaction of vinylboronates can be easily performed using microwave irradiation giving excellent yields of the cycloadducts. Pinacol vinylboronate was the reagent of choice due to its stability towards hydrolysis, operational simplicity and yields of Diels-Alder products. To the best of our knowledge, this is the first example of microwave-assisted Diels-Alder reaction of boron-substituted dienophiles. Subsequent in situ oxidation of the cycloadducts with alkaline hydrogen peroxide afforded the alcohols efficiently.
Assuntos
Ácidos Borônicos/química , Química Orgânica/métodos , Micro-Ondas , Modelos Químicos , Compostos de Vinila/química , OxirreduçãoRESUMO
An assessment of the relative O-3/O-4 reactivities of both methyl alpha- and beta-d-glycosides of N-dimethylmaleoyl (DMM) d-glucosamine acceptors protected at O-6 with benzoyl (Bz), benzyl (Bn), and tert-butyldiphenylsilyl (TBDPS) groups is presented using per-O-benzoylated beta-d-galactofuranosyl and per-O-acetylated alpha-d-galactopyranosyl trichloroacetimidates as glycosyl donors. Using the former donor, the alpha anomer of the 6-O-benzoylated compound gave exclusive substitution at O-3, whereas the other two compounds with alpha-configuration kept this site as preferential. The beta anomer of the 6-O-benzoylated compound gave the same amounts of reaction products on O-3 and O-4, whereas the other beta analogs carried a more reactive O-4. The same reactions were carried out using as donor the less-reactive per-O-acetylated alpha-d-galactopyranosyl trichloroacetimidate. Although the same trend was found to occur, the O-4 was always relatively more reactive with the pyranosyl donor than with the furanosyl donor, when keeping the remaining factors constant. Furthermore, the beta anomers of the acceptor gave almost exclusive substitution at O-4. These observations confirm and extend the utility of these 'matching' donor and acceptor reactivities.