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Gas–solid reactions between the different polymorphic modifications of barbituric acid and amines

“…Such reactions have been exploited with crown ethers and calixarenes 19 metalloporphyrins immobilized on reverse-phase silica and on hydrophobic membranes, 18,20,21 with molecularly imprinted sensor arrays 22 and with organic hosts. 23 The aim of this work is to investigate the gas-solid reaction of a weak non-carboxylic acid such as barbituric acid with a series of amines. The work builds on our experience with gas solid reactions involving organometallic acids and organic bases.…”

Unsymmetrical Derivatives of Gossypol: A Review

“…The term unsymmetrical derivatives of gossypol first was suggested by S.A. Talipov and co-authors in 1997. They applied this term for gossypol half-Schiff bases with ammonia (Table ; 2) and methyl amine (Table ; 3) [1]. However, gossypol derivatives with only one functional substituent have been already known before their research.…”

“…In 1997 S.A. Talipov and coworkers [1] reported on solid-state reaction conditions allowing to prepare unsymmetrical gossypol Schiff's bases with ammonia and methyl amine. The crystals of gossypol P3 polymorph used for this reaction have wide empty channels with one of gossypol's two aldehyde groups located near the channel wall, which makes possible to unsymmetrically modify gossypol molecule.…”

“…The crystals of gossypol P3 polymorph used for this reaction have wide empty channels with one of gossypol's two aldehyde groups located near the channel wall, which makes possible to unsymmetrically modify gossypol molecule. Authors have demonstrated that this chemo-sorption is highly exothermic [1]; however, this fact has not been taken into consideration in order to optimize the yield of the target products. Moreover, none of the resulting gossypol half-Schiff bases has been tested for any biological activity.…”

“…To create the same as in solid state reaction partial unavailability of gossypol's one aldehyde group for reaction with aminocompounds they applied high dilution technique, so amine was added to diluted gossypol solution that was cooled as well as amine solution. It is known that reaction of Schiff base formation is exothermic [1], which has been taken into account during experiment. Relatively low solubility of gossypol half-Schiff bases in chloroform and ethyl acetate at -15 ° allowed applying precipitation followed by Silica gel column separation of target products.…”