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The reactions of cytisine with glycidyl ethers of 3-arylcoumarins were studied. A series of cytisine–coumarin conjugates were synthesized via regiospecific opening of the oxirane ring by cytisine. Methods for conjugating anabasine and cytisine with 3-arylcoumarins through a but-2-ynyl linker via reactions of propargyl ethers of 7-hydroxy- and 6-hydroxy-3-arylcoumarins with the alkaloids were proposed.

The over-accumulation of glycogen appears as a hallmark in various glycogen storage diseases (GSDs), including Pompe, Cori, Andersen and Lafora disease. Accumulating evidence suggests that suppression of glycogen accumulation represents a potential therapeutic approach for treating these GSDs. Using a fluorescence polarization assay designed to screen for inhibitors of the key glycogen synthetic enzyme, glycogen synthase (GS), we identified a substituted imidazole, (rac)-2-methoxy-4-(1-(2-(1-methylpyrrolidin-2-yl)ethyl)-4-phenyl-1H-imidazol-5-yl)phenol (H23), as a first-in-class inhibitor for yeast glycogen synthase 2 (yGsy2p). Data from X-ray crystallography at 2.85 Å, as well as kinetic data, revealed that H23 bound within the UDP-glucose binding pocket of yGsy2p. The high conservation of residues between human and yeast GS in direct contact with H23 informed the development of around 500 H23 analogs. These analogs produced a structure-activity relationship (SAR) profile that led to the identification of a substituted pyrazole, 4-(4-(4-hydroxyphenyl)-3-(trifluoromethyl)-1H-pyrazol-5-yl)pyrogallol, with 300-fold improved potency against human GS. These substituted pyrazoles possess a promising scaffold for drug development efforts targeting GS activity in GSDs associated with excess glycogen accumulation.

The transformations of 7-dimethylaminomethyl-6-hydroxyaurone and 5-dimethylaminomethyl-6-hydroxy-7-methylurone in the inversed electron-demand hetero-Diels–Alder reaction were studied. As a result of in situ thermal formation of o-quinone methides containing the benzofuranone moiety and cycloaddition of cyclic vinyl esters, 2-benzylidene derivatives of difuro[2,3-b:2',3'-f]chromen-3(2H)-one, furo[2,3-f]pyrano[2,3-b]chromen-3(2H)-one, difuro[2,3-b:3',2'-g]chromen-3(2H)-one, and furo[3,2-g]pyrano[2,3-b]chromen-3(2H)-one heterocyclic systems were synthesized. A similar reaction with cyclic enamines, accompanied by subsequent transformation of hemi-aminals, led to the formation of partially hydrogenated derivatives of furo[2,3-a]xanthen-3(2H)-one and furo[3,2-b]xanthen-3(2H)-one.

The possibility of using the alkaloid anabasine in Mannich aminomethylation of coumarins was studied. Anabasine-coumarin conjugates in which the benzopyrone core was conjugated to anabasine through a methylene linker were synthesized.

Reaction features of polyhydroxydeoxybenzoins and their heteroatomic analogs with succinic and glutaric anhydrides were studied and shown to be useful for synthesizing 3-(3-pyrazolyl)butyric acids and 4,11-dioxo-8,10,11,12-tetrahydro-4H,9H-pyrano[2,3-a]xanthene derivatives with a butyric acid moiety.

Possible Mannich aminomethylation of isoflavone chromone rings was studied using the alkaloid anabasine. Anabasine-isoflavone conjugates in which the benzopyrone core was connected to anabasine through a methylene linker were synthesized.

Aminomethylation of the natural isoflavones afromosin and cladrastin and their 2-methyl derivatives was studied. Several new Mannich bases of 7-hydroxy-6-methoxyisoflavones were synthesized under Mannich reaction conditions using aminals of secondary amines.

Recyclization by hydrazine of furo[3,2-b]pyrano[2,3-f]chromen-4-ones, dipyrano[2,3-b:2,3-f]chromen4-ones, and pyrano[2,3-a]xanthen-4-ones derived from natural isoflavonoids and their analogs was studied. The reaction was shown to proceed selectively with opening of the chromone ring. Several substituted 4-arylpyrazoles containing furo[3,2-b]chromen-5-ol, pyrano[2,3-b]chromen-6-ol, and xanthen-8-ol fragments were synthesized.

A reliable method for the synthesis of B-ring hydroxylated homoisoflavonoids and 3-hetarylmethyl chromones has been developed. The method involves an initial oxa-Diels-Alder reaction of ortho-quinone methides generated from aryl/hetaryl-substituted ortho-( N, N-dimethylaminomethyl)phenols with (2 E)-3-( N, N-dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-ones and the subsequent cascade of reactions. This synthetic strategy avoids conventional multistep protocols and does not require the protection of hydroxyl groups, thus allowing the facile synthesis of a library of various aromatic and heterocyclic analogues of naturally occurring homoisoflavonoids.

The behavior of flavonoid Mannich bases in inverse electron-demand hetero-Diels–Alder reactions was studied. Isoflavones and aurones were used as examples to show that their Mannich bases reacted with 4-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)morpholine through an elimination mechanism and subsequent cycloaddition to form derivatives of the new heterocyclic systems pyrano[2′,3′:5,6]chromeno[3,2-c]pyridin-4-one and furo[2′,3′:5,6]chromeno[3,2-c]pyridin-3(2H)-one.

The reactivity of Mannich bases derived from 6- and 7-hydroxycoumarins was studied in inverse electron demand Diels–Alder reactions with enamines. The reactions were shown to proceed by a cycloaddition mechanism followed by transformation of hemiaminals and resulted in the formation of heterocyclic pyrano[2,3-a]xanthene, pyrano[2,3-b]xanthene, and pyrano[3,2-b]xanthene.

A simple method of the synthesis of α-(3(5)-trifluoromethylpyrazol-5(3)-yl)-2-hydroxydeoxybenzoins by a chemoselective reaction of 2-(1,1,1-trifluoroacetonyl)chromones with hydrazine dihydrochloride was developed. This approach involves the initial attack of hydrazine at the carbonyl atom of the CF3C(O)CH2 group followed by the chromone ring opening at C-2 atom and subsequent cyclization to pyrazoles. Such synthetic strategy provides easy access to the novel type of pharmaceutically attractive 3-(trifluomethyl)pyrazole-deoxybenzoin hybrids in high yields.

Chromones play an important role in the design and discovery of new pharmacologically active compounds. A large volume of reports dedicated to synthesis and study of properties of nitrogen-containing chromone derivatives show important role of chromone alkaloid-like compounds. The present review covers achievements in the field of synthesis of chromone aminomethyl derivatives as one of perspective scaffolds.

A synthetic method for 7-hydroxy-5-methoxyisoflavones starting from 5,7-dihydroxyisoflavones was developed. Dimethylcarbamoylchloride was proposed for protection of the 7-hydroxy group. Aminomethylation of the synthesized 7-hydroxy-5-methoxyisoflavones by formaldehyde aminals was studied.

Aminomethylation of natural isoflavones by amino acids was studied. Conditions for selective production of N-(4H-4-oxochromen-8-yl)methyl-substituted amino acids were found.

The regioselective condensations of various 7-hydroxyisoflavonoids with bis(N,N-dimethylamino)methane in a Mannich reaction provided C-8 N,N-dimethylaminomethyl-substituted isoflavonoids in good yield. Similar condensations of 7-hydroxy-8-methylisoflavonoids led to the C-6-substituted analogs. Thermal eliminations of dimethylamine from these C-6 or C-8 N,N-dimethylaminomethyl-substituted isoflavonoids generated ortho-quinone methide intermediates within isoflavonoid frameworks for the first time. Despite other potential competing outcomes, these ortho-quinone methide intermediates trapped dienophiles including 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, 3-(N,N-dimethylamino)-5,5-dimethyl-2-cyclohexen-1-one, 1-morpholinocyclopentene, and 1-morpholinocyclohexene to give various inverse electron-demand Diels-Alder adducts. Several adducts derived from 8-N,N-dimethylaminomethyl-substituted isoflavonoids displayed good activity in the 1-10 μm concentration range in an in vitro proliferation assay using the PC-3 prostate cancer cell line.

The regiospecific Mannich aminomethylation of 7-hydroxyisoflavonoids using bis(N,N-dimethylamino)methane afforded C-8 substituted N,N-dimethylaminomethyl adducts, and the regioselective aminomethylation of 5-hydroxy-7-methoxyisoflavonoids afforded predominantly the C-6 substituted N,N-dimethylaminomethyl adducts. Acetylation of these C-6 or C-8 Mannich bases with potassium acetate in acetic anhydride provided access to the corresponding acetoxymethyl derivatives that were subsequently converted to hydroxymethyl- and methoxymethyl-substituted 5-hydroxy- or 7-hydroxyisoflavonoids related to naturally occurring flavonoids. The C-8 acetoxymethyl, hydroxymethyl or methoxymethyl-substituted isoflavonoids possessed promising inhibitory potency in the low micromolar range in a prostate cancer PC-3 cell proliferation assay.