Band 18, Heft 3

The reaction of 6-chloropurine ( 1 ) with fourfold excess of hydroxylamine- O -sulfonic acid (HOSA) provided (Z)-1 H -purin-6-ylideneaminooxysulfonic acid ( 2 ) which can be regarded as a secondary metabolite of ultimate mutagen 6-hydroxylaminopurine (6-HAP). A similar reaction of 1 with twofold excess of HOSA gave a mixture of the substrate and the betaine product which co-crystallized from DMF-methanol-water in the form of complex 3 that proved to be a 1:1 complex 1·2 with offset face-to-face π-stacking interactions between purine rings.

Novel heterocyclic enamine derivatives based on skeleton of neonicotinoids were designed and prepared by the substitution reaction between heterocyclic enamines with intermediates of neonicotinoids, which provides readily accessible neonicotinoid analogs for potential bioactivity assay.

6-Acetyl-7-methylpteridine derivatives 2 and 3 (lumazine and pterin) were converted to 6-[1-(arylamino)ethyl]pteridine derivatives 8 and 7 , respectively, in good to moderate yields by stepwise reactions with p -substituted anilines via imine intermediates using a Lewis acid catalyst followed by treatment with sodium tetrahydroborate. The one-step reductive amination of the starting acetylpteridine also proceeded in the presence of 2-picoline-borane complex in satisfactory yield.

Four phthalazine derivatives have been prepared from substituted 2-bromobenzaldehyde acetals by a sequence involving: (1) lithiation and formylation; (2) deprotection; and (3) condensative cyclization with hydrazine. Two additional phthalazines were prepared by a similar sequence following direct lithiation of benzaldehyde acetals substituted by anion-stabilizing groups at C3. These syntheses can be conveniently carried out to give phthalazines in overall yields of 40–70%.

Cyanuric chloride was allowed to react with N,N -diethylaniline to obtain 4-(4,6-dichloro-1,3,5-triazin-2-yl)- N,N -diethylaniline, which was converted into six novel 1,3,5-trisubstituted triazine derivatives on reaction with different amino acids. These compounds had UV absorption in the range 352–379 nm, accompanied by intense single emission in the range 420–497 nm with fairly good quantum yield (0.106–0.383). The new compounds were characterized by FT-IR, 1 H NMR, 13 C NMR, mass spectral, and elemental analyses. These fluorophores were conjugated with protein bovine serum albumin through carbodiimide chemistry between the negatively charged carboxylate groups (-COO-) of the fluorophore and the surface terminated positively charged amino groups (-NH 3 + ) of the protein. The interaction between functionalized amino acids with protein molecules was investigated using fluorescence spectroscopy showing fluorescence enhancement or quenching of the fluorophore after conjugation.

Two series of novel 3-cyano-2-(2′′,3′′,4′′-tri- O -acetyl- β - D -arabinopyranosyloxy)pyridones 5a–h and 9a,b were synthesized. Microwave irradiation has been used to obtain these products in high yield under milder conditions by the reaction of 2(1 H )-pyridone or its salt with an activated arabinose. The silyl method was used to obtain the same nuclesides 5a–h and 9a,b . Triethylamine was used to remove the acetyl protecting groups from the sugar moiety and to produce the free nucleosides 6a–h and 10a,b in 85–91% yield.

An easy synthetic route to N -dichloroacetyl-3,4-dihydro-2 H -1,4-benzoxazine derivatives 3 involves cyclization of 2-aminophenols 1 with 1,2-dibromoethane and subsequent acylation of the resultant 3,4-dihydro-2 H -1,4-benzoxazine derivatives 2 with dichloroacetyl chloride. All compounds were characterized by IR, 1 H NMR, 13 C NMR, ESI-MS and elemental analysis. The structure of 3a was determined by X-ray crystallographic analysis.

Reaction of N,N -diallyl- p -toluenesulfonamide 1 with benzyl halides 2 in the presence of a palladium catalyst afforded a series of novel dihydropyrroles 3 in moderate yields. A palladium-catalyzed self-cyclization reaction of the diene 1 may take place to give a cyclic dihydropyrrole 4 during the reaction. It is proposed that the cyclic products 4 are formed via a palladium-catalyzed cascade cyclization-coupling process. Reaction of phenyl iodide 5 with 1 in the same condition afforded normal Heck vinylation products 6 .

A series of ethyl 5-aryl-1,2-dihydroanthra[2,1- c ][2,7]naphthyridine-3(4 H )-carboxylate derivatives was prepared by a three-component reaction of aromatic aldehyde, anthracen-2-amine and ethyl 4-oxopiperidine-1-carboxylate using iodine as catalyst. This iodine-catalyzed procedure has the advantages of mild reaction conditions, good yields, operational simplicity and metal-free catalyst.

Eleven new 8-[(alkyl or aryl)amino]-9-(alkyl or aryl)acenaphtho[1,2- b ]pyrroles were synthesized by one-pot reaction of (acenaphthylen-1-yloxy)trimethylsilane, alkyl or aryl aldehyde, ammonium acetate, and aryl or alkyl isocyanide in refluxing DMF.

Thiadiazole compounds including 3-hydroxy-4-substituted-1,2,5-thiadiazole are known as non-nucleoside inhibitors of HIV-1. Density functional calculations at the B3LYP/6-311++G(d,p) level were employed to determine the stability, tautomerism, and substituent effects of 1,2,5-thiadiazole, a widely used skin-whitening, antibrowning, and antibacterial agent, and its derivatives (4-NO 2 , 4-CN, 4-F, 4-H, 4-Me, 4-NH 2 ), in the gas phase and solution using the polarizable continuum method model. Some selected IR frequencies, molecular parameters, charges on atoms, and dipole moment results were analyzed.