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311.
Margherita De Rosa 《Tetrahedron letters》2006,47(48):8507-8510
This letter describes the first example of diastereoselective ‘organocatalyzed’ synthesis of the butenolide products substituted at the γ-position by a chain bearing hydroxyl groups. The urea-derivative 4 has proved to be an efficient catalyst for the addition of the commercial TMSOF to carbonyl compounds under solvent-free conditions. The reaction conditions and generality of the procedure have been examined. 相似文献
312.
Cardullo F Donati D Fusillo V Merlo G Paio A Salaris M Solinas A Taddei M 《Journal of combinatorial chemistry》2006,8(6):834-840
One of the still unresolved problems in parallel synthesis is the availability of a general and rapid method for the transformation of a primary amine into the corresponding secondary amine without the issue of polyalkylation. Following the Fukuyama method, which is based on the alkylation of o-nitrobenzenesulfonamides, followed by removal of the sulfonyl group, we have developed a simple protocol which can be easily applied to parallel synthesis making use of supported reagents and scavengers. To verify the robustness of the method, a small representative array of secondary amines have been prepared. Moreover, taking advantage of the possibility to use different supported reagents in the same pot, we also prepared, starting from primary amines, a series of differently substituted tertiary amines. 相似文献
313.
Ciavatta ML Lopez Gresa MP Gavagnin M Manzo E Mollo E D'Souza L Cimino G 《Molecules (Basel, Switzerland)》2006,11(10):808-816
Chemical analysis of the secondary metabolite pattern of the sacoglossan mollusc Elysia cf. expansa, collected along South Indian coasts, showed the presence of the typical Caulerpa-derived sesquiterpene caulerpenyne (1) and two new minor co- occurring metabolites, the compounds dihydrocaulerpenyne (4) and expansinol (5). The chemical characterization of these molecules, structurally related to 1, is reported. 相似文献
314.
Marianna Carbone Antonella Daniele Alessia Ligresti Margherita Gavagnin 《Tetrahedron》2010,66(49):9497-9501
The chemical analysis of a sample of Δ9-THC, which had been stored in an ethanol/propylene glycol solution for 5 years, resulted in the isolation of several hydroxylated Δ9-THC derivatives, the main of which were trans-cannabitriol monoethyl ether (4) and trans-propanediol ethers 7 and 8. cis-Cannabitriol monoethyl ether (5) and the oxidised derivatives 3 and 6 were detected in lesser amounts. The structure elucidation of the unprecedented cannabinoids 3, 5, 7 and 8 was achieved mainly by NMR techniques. Full NMR assignment of compounds 4 and 6 were also made. The detection of cannabitriol (6) and the corresponding solvent-adduct analogues (compounds 4-8) was in agreement with the decomposition mechanisms previously proposed for Δ9-THC. The isolation of the endoperoxide 3 represents indirect evidence of the existence of unstable precursors that were suspected to be intermediates in the non-enzymatic oxidation pathway of Δ9-THC. Both isomers of cannabitriol monoethyl ether exhibited weak affinity at either CB1 (Ki=2.25, 6.30 μM) or CB2 cannabinoid receptors (Ki=1.97, 3.13 μM), the trans isomer always being more potent than the cis isomer. 相似文献
315.
Elena Amico di Meane Margherita Plassa Francesca Rolle Michela Sega 《Accreditation and quality assurance》2009,14(11):607-611
Metrologically traceable measurements are needed, in environmental monitoring, to provide meaningful information on the pollution
level and the possibility to have suitable reference standards is crucial to this purpose to calibrate instruments. The Italian
National Institute of Metrological Research (I.N.Ri.M.), as a primary metrological institute, realizes and maintains primary
standards for the basic and derived units of the International System of Units (SI). In this framework and regarding gas analysis,
in the last few years I.N.Ri.M. has started a research line on the preparation of primary reference mixtures (PRMs) by the
gravimetric method that led to plan and build a facility for evacuating and filling cylinders and a device for high precision
weighing. In the present work the developments in such field at I.N.Ri.M. are reported to underline the relevance, in the
atmospheric pollutants monitoring, of performing accurate and reliable measurements and having reference standards fit for
the calibration of the analytical instrumentation. 相似文献
316.
In this paper we study the Brill–Noether theory of invertible subsheaves of a general, stable rank-two vector bundle on a
curve C with general moduli. We relate this theory to the geometry of unisecant curves on smooth, non-special scrolls with hyperplane
sections isomorphic to C. Most of our results are based on degeneration techniques.
The first three authors are members of G.N.S.A.G.A. at I.N.d.A.M. “Francesco Severi”. 相似文献
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