N. A. Lozinskaya

Reaction of Aromatic Aldehydes with Ammonium Acetate

By reaction of aromatic aldehydes with ammonium acetate a series of 1,2-diaryl-1,2-diaminoethanes and their derivatives was obtained. The mechanism of reaction was suggested and its principal stages were proved. Reactions with ammonium acetate of aromatic aldehydes containing ortho-substituents resulted in the corresponding 2,4,5-triaryl-4,5-dihydroimidazoles.

Regioselective synthesis of cis- and trans-2,4,5-triarylimidazolines and 2,4,5-triarylimidazoles from available reagents

Novel data were obtained concerning the reaction of aromatic aldehydes with ammonia. A preparative method for the synthesis of new substituted 1,3,5-triaryl-2,4-diazapenta-1,4-dienes was developed. These products are the starting reactants for syntheses of cis- and trans-2,4,5-triaryl-2-imidazolines and 2,4,5-triarylimidazoles.

Synthesis of novel МТ3 receptor ligands via an unusual Knoevenagel condensation

New 5-acetamido-substituted melatonin derivatives were efficiently synthesized in excellent yields via Knoevenagel condensation. The relative binding affinity of new synthesized compounds to MT3 receptor was tested via enzymatic assays and the X-ray structures of the most potent compounds were determined in complex with MT3.

Electrophilic substitution in aromatic and heteroaromatic substrates by trichlorocyclopropenylium tetrachloroaluminate

Trichlorocyclopropenylium tetrachloroaluminate is an electrophilic reagent for the preparative introduction of a cyclopropenyl fragment into heteroaromatic and aromatic substrates.

Novel agonists of melatonin receptors as promising hypotensive and neuroprotective agents for therapy of glaucoma

Melatonin is a pineal hormone that has a capacity to lower intraocular pressure; it exhibits neuroprotective and antioxidant properties that make it possible to use melatonin in the therapy of glaucoma. Melatonin analogs demonstrating affinity to melatonin receptors are promising candidates for application as antiglaucomatous agents. Chemical modification of the melatonin structure can increase efficiency, bioavailability, and selectivity of melatonin analogs. We have designed and synthesized a number of new 2-oxindole derivatives, the ligands of melatonin MT3 receptors; these analogs are characterized by the ability to lower intraocular pressure in normotensive rabbits and high antioxidant activity against hydroxyl radical and superoxide anion-radical. New ligands significantly exceeding melatonin in antioxidant activity can be also applicable for the development of therapeutic agents for treatment of oxidative stress. The maximal hypotensive effect of the analogs was comparable to and lasted longer than that of melatonin. Combination of these properties suggests potential used of the analyzed melatonin analogs in complex therapy of glaucoma.

Effect of melatonin instillations on the clinical course of experimental uveitis and biochemical processes in tears and aqueous humor

Acute immunogenic uveitis was modeled in rabbits via the subcutaneous and intravitreal injections of normal horse serum. We studied the effect of instillations of 0.1% melatonin solution on the clinical course of uveitis and biochemical parameters of tear fluid and aqueous humor: antioxi-dant activity, protein concentration and α(2)-macroglobulin level. Melatonin instillations decreased clinical manifestations of uveitis. We found that the antioxidant activity in tears of the rabbits treated with melatonin was substantially higher and the α(2)-macroglobulin level lower than in untreated animals. Antioxidant activity in aqueous humor taken on day 10 of uveitis was also twice higher while protein and α(2)-macroglobulin levels were 1.5-2 times lower than in untreated animals. These data indicate that instillations of melatonin increase the local antioxidant activity and decrease the acuity of inflammation and permeability of hematoophthalmic barrier in uveitis.

Synthesis of N-(2,2,2-trichloro-1-hydroxyethyl)aldimines and their derivatives

The preparative procedure for the synthesis of N-(2,2,2-trichloro-1-hydroxyethyl)aldimines from the corresponding aldehyde, chloral, and ammonium acetate was developed. Preparative silylation and acylation of their hydroxy groups were acomplished for the first time. The possibility to use the synthesized O-trimethylsilyl and O-acetyl derivatives as the synthetic equivalents of N-nonsubstituted imines in the reactions with cyclopropenone was investigated.

Stable synthetic equivalents of N-unsubstituted imines: Part 1. Synthesis

The key role of imines in organic synthesis, for example in the synthesis of amine derivatives and nitrogen heterocycles, is well known. However, the instability of N-unsubstituted imines is often an obstacle to the selection of synthesis strategy. Therefore, it is rather topical to design stable imines with a readily removable group at the nitrogen atom. The first part of this review deals with the methods of synthesis of N-sulfinyl imines (including chiral), N-sulfonyl imines, N-phosphinoyl imines, N-acylimines, N-silylimines, N-(hexopyranosyl)imines, N-benzylimines, N-(methoxyphenyl)imines, N-allylimines, 1,3,5-trisubstituted 2,4-diazapenta-1,4-dienes, and N-(1-hydroxyethyl-2,2,2-trichloro)imines and the methods for removing these protective groups.

Stereoselective synthesis of 1,2-diamino-1,2-diarylethane derivatives

A procedure was developed for selective opening of the cis-2,4,5-triarylimidazoline ring to form erythro-1,2-diamino-1,2-diarylethane derivatives. These ring-opening products, erythro-ethylenediamine derivatives, can undergo quantitative isomerization to threo-ethylenediamine derivatives in the presence of strong bases in DMSO.