The oxidative dimerization of glycinates 1 with iodine takes place under kinetic control. The stereochemistry of the resulting 3-aminoaspartate 3 depends on the method used (base/solvent) to generate the corresponding enolate 2. Under suitable conditions, high yields and diastereomeric excesses in favor of the threo derivatives 3-I, which have C(2) symmetry, were obtained. In the presence of 8-phenylmenthol as chiral auxiliary (2S, 3S)-3-aminoaspartic acid 5-I was synthesized.
Wittig-Horner reactions under interfacial solid-liquid conditions using activated barium hydroxide catalyst C-200 produce acyclic a-enones with high yields and selectivities.The Wittig-Horner reaction is a versatile method for preparation of unsaturated compounds and its synthetic aspects have been widely studied'. Recently, the process has been carried out using two-phase liquid-liquid2 or solid-liquid conditionsss and better yields were obtained than those achieved under classical conditions. Nevertheless, undesired side reactions of starting materials (crotonization, Cannizzaro reaction, etc.) and products (e.g. double bond shifts) have often been observed.2+-7We recently described a new microcrystalline solid basic catalyst, C-200 [Ba(OH)2-0.8H20]9 and its catalytic activity in several organic reactions in solid-liquid media, e.g.
A new synthesis of 9-hydroxy- and 9-(alkylamino)thiazolo[5,4-b]quinolines by cyclization of 4-(ethoxycarbonyl)-5-(arylamino)thiazoles and 5-(arylamino)-4-carbamoylthiazoles, respectively, is described. In vitro cytotoxicity of a large number of derivatives of these compounds has been tested against several cell lines. The highest activities observed are associated with the presence of a 2-[[(N,N-diethylamino)ethyl]amino] substituent at C-2 and a fluorine atom at the C-7 position of the tricyclic planar heteroaromatic framework. Three structural features seem to be essential for antitumor activities: a positive charge density at carbon C-7, a side chain at position C-2 or C-9 of the thiazoloquinoline skeleton with two basic nitrogens and a pKa value of 7.5-10 in the most basic center, and a conformational flexibility of this basic side chain. These structural requirements must be simultaneously satisfied in order to ensure a significant antitumor activity.
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