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11.
Antonino Corsaro Ugo Chiacchio Venerando Pistarà Roberto Romeo Felicia D'Andrea Emanuele Attolino 《Tetrahedron》2004,60(17):3787-3795
Completely protected 4-deoxy-α-L-threo-hex-4-enopyranosides 1c,d undergo the dichlorocarbene addition affording exclusively diastereomeric adducts 5c,d with the cyclopropane ring anti to the C-3 alkyloxy substituent, while the reaction with 3-unprotected derivatives 1a,b affords a mixture of syn and anti derivatives. Under the Simmons-Smith cyclopropanation adducts 2a-d with a syn stereochemistry are obtained. Starting from 5b, the cyclopropanated sugar 3b is obtained by reduction with LiAlH4, thus the two diastereomers 2b and 3b can be stereoselectively obtained through the two different pathways. For a useful comparison, 4-deoxy-β-L-threo-hex-4-enopyranoside 1e was also subjected to the above two cyclopropanation methods affording the expected cycloadduct 2e and a diastereomeric mixture of dichlorocycloadducts 4e and 5e (4e/5e=2.8:1). 相似文献
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Pedro Merino Graziella Greco Tomás Tejero Ramon Hurtado-Guerrero Rosa Matute Ugo Chiacchio Antonino Corsaro Venerando Pistarà Roberto Romeo 《Tetrahedron》2013
Diastereoselective asymmetric 1,3-dipolar cycloadditions of N-(alkoxycarbonylmethyl) nitrones derived from glycine, alanine and phenylalanine have been studied both experimentally and theoretically. Asymmetric induction is evaluated by either introducing a chiral group at the nitrone nitrogen atom or by using Oppolzer's sultam acrylamide. In both cases the sense of the asymmetric induction is the same, the (3R,5R)-isomer being preferentially obtained. The best results were observed with the chiral dipolarophile, which afforded an only isomer in all cases. The obtained isoxazolidines are easily transformed into the corresponding 5-substituted-3-hydroxypyrrolidin-2-ones. DFT studies are in a qualitative agreement with the observed experimental results. 相似文献
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Ab Initio MP2 and Density Functional Theory Computational Study of AcAlaNH2 Peptide Hydration: A Bottom‐Up Approach 下载免费PDF全文
AcAlaNH2?n H2O (n=1–13) complexes have been proposed as models to account for water solvent effects on the molecular properties of N‐acetyl‐L ‐alanine amide. Ab initio computations are planned to evaluate peptide–water interactions and to provide a means for approximating relative effects of the short‐range many‐body interactions arising in real solution without introducing any external parameters intended to quantify empirical or semiempirical potential‐energy functions. The present bottom‐up approach reveals the formation of compact ring clusters of water molecules strongly bonded to peptidic polar groups throughout hydrogen bonds. The explicit coordination of water molecules around the peptide renders the fully extended (FE) and polyproline II (PPII) conformers more stable with respect to the 310 helix or γ turn. The alternance of donor and acceptor groups on both sides of the FE and PPII conformers allows for synergy and extensive H‐bonding. 相似文献
14.
Antonino Corsaro Ugo Chiacchio Giancarlo Perrini Pierluigi Caramella Franca Marinone Albini 《Journal of heterocyclic chemistry》1989,26(6):1691-1699
A study on the acetylation and benzoylation of title compounds by quenching the corresponding 4-carbanions with acyl chlorides or esters is reported. The obtained ketones are formed as minor regioisomeric adducts in the cycloadditions of benzo and mesitonitrile oxide to methyl and phenyl vinyl ketone. The quenching with methyl chloroformate was also examined as a possible convenient route to 4-methoxycarbonyl-3-aryl-4,5-dihydroisoxazoles. 相似文献
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In this paper we consider the following class of linear elliptic problems
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An efficient synthesis of pyrimidine-containing butenolides is reported, starting from C-alkoxycarbonyl isoxazolidines. Two competitive reaction routes are operating: the pathway leading to homo-N,O-nucleosides, based on the reduction of an ester group at C3, and the reaction channel leading to butenolides promoted by the removal of the hydrogen atom at C3. The two reaction pathways can be easily controlled according to the adopted experimental conditions 相似文献
18.
Blanco Ignazio Bottino Francesco A. Bottino Paola Chiacchio Maria A. 《Journal of Thermal Analysis and Calorimetry》2018,134(2):1337-1344
Journal of Thermal Analysis and Calorimetry - Two novel 4-methyl phenyl (trioxyisobutyl POSS) silane and 4-methyl phenyl (trioxycyclopentyl POSS) silane were synthesized. The nanosystems were... 相似文献
19.
Chiacchio U Rescifina A Saita MG Iannazzo D Romeo G Mates JA Tejero T Merino P 《The Journal of organic chemistry》2005,70(22):8991-9001
[reaction: see text] The cycloaddition reaction between C-(2-thiazolyl) nitrones and allylic alcohol takes place with complete exo selectivity when the reactions are carried out in the presence of 1 equiv of zinc triflate. The rate of the reaction is increased enormously under microwave irradiation. The use of a chiral dipolarophile allowed application of the methodology to the synthesis of a hitherto unknown enantiomerically pure isoxazolidinyl analogue of the C-nucleoside tiazofurin. 相似文献
20.
Anna Compagnini Adriana Lo Vullo Ugo Chiacchio Antonio Corsaro Giovanni Purrello 《Journal of heterocyclic chemistry》1982,19(3):641-643
The title reaction affords to the adducts 3 which upon alkaline treatment give compounds 5 , while by thermolysis give 6 and 7 . Hydrochloride salts of 3 in refluxing xylene afford to chlorohydrazones 10 as the major products. A mechanism is proposed for thermal decomposition of 3. 相似文献