Fulgides are a class of organic compounds that undergo photochromically reversible color and structural changes, called photochromism. This property has a number of practically beneficial implications including optical data storage, waveguides, holograms, photochromic lenses, integrated optics, sunlight attenuation, and sensor protection. We have synthesized two isomeric fulgides, I (E) and I (Z), and have discovered that only the I (E) isomer exhibits photochromism. Thus, upon irradiation with a UV light at max 350 nm, the nearly colorless I (E) undergoes conrotatory electrocyclic ring-closure to form the colored cyclized product II which absorbs in the visible region at max ~600 nm. The colored product II reverts back to colorless I (E) upon irradiation with a visible light at max ~530 nm. The I (Z) isomer, on the other hand, is unable to cyclize under the same conditions, apparently because of its structural constraints for cyclization. We reasoned that the introduction of additional conjugation in the molecule would facilitate photochemical isomerization of the Z isomer into the required E form for cyclization with UV irradiation. To this end, compounds III (E) and III (Z) were synthesized from I (E) and I (Z), respectively, and were both found to exhibit photochromism. Another added advantage of enhanced conjugations in III (E) and III (Z), as compared with I (E) and I (Z), is the absorbance at a higher wavelength (max ~620 nm) region. The latter property is anticipated to improve semiconductor laser compatibility of fulgides. It is believed that for a sufficiently high decoding (erasure) sensitivity, the colored products must exhibit absorbance in considerably long wavelength (visible) region.

2,6-Diaminopurines as well as their nucleoside and nucleotide analogues have attracted considerable attention in recent years as potential antiviral and antitumor compounds. Some of these compounds have already been shown to be potent anti-HIV agents, including 2',3'-dideoxy-2,6-diaminopurine-9--D-ribofuranoside (I), the acyclic nucleotide analogue 9-[2-(phosphonylmethoxyethyl)]-2,6-diaminopurine (II), and the three carbocyclic nucleoside analogues ( )-cis-[4'-(2,6-diamino-9H- purin-9-yl)-2-cyclopentenyl]carbinol (III), ( )-cis-[3'-(2,6-diamino-9H-purin-9-yl)cyclopentyl] carbinol (IV), and ( )-9-[2',3'-bis(hydroxymethyl)]cyclobutyl-2,6-diaminopurine (V). As part of a program to improve profiles of drug efficiency and toxicity of 2,6-diaminopurine nucleoside analogues, it became necessary to explore the structure-activity relationships (SAR) via specific modifications at the N6-position of 2,6-diaminopurine ring. However, all available conventional methods to accomplish this goal, including the alkylation of the N6-amino group of 2,6-diaminopurine riboside or the displacement of a halogen group of 2-amino-6-chloropurine riboside yielded intractable mixtures of products and/or poor yields. We report here the synthesis of a versatile, highly reactive precursor (VI), which upon reaction with amine nucleophiles, gave the desired, specifically N6-modified 2,6-diaminopurinepurine nucleosides (VII) in high yields. In addition, the reaction of VI with polymethylenediamines afforded the polymethylene-bridged dimers of 2,6-diaminopurine nucleosides (VIII).

Ring-expanded ("fat") nucleosides and nucleotides are potentially useful probes for nucleic acid metabolism, structure, and function. With their structural resemblance to natural purines, they are a rich source of substrates or inhibitors of enzymes of nucleic acid metabolism as well as of those requiring energy cofactors such as ATP or GTP. As ring-expansion is anticipated to considerably affect the electronic, spatial, and geometric characteristics, they are also excellent probes for steric and conformational constraints of nucleic acid double-helices.

A number of acyclic nucleosides and nucleoside phosphonates have exhibited potent antiviral activities in recent years, and many of them have been approved by U.S. Food and Drug Administration (FDA) for a variety of viral infections. These include, but are not limited to, Acyclovir (I) for herpes simplex virus (HSV I and HSV II), Ganciclovir (II) for human cytomegalovirus (HCMV), Penciclovir (III) and Adefovir (PMEA) (IV) for hepatitis B virus (HBV). We have recently reported the synthesis and potent anti-HBV activity of a ring-expanded ("fat") nucleoside (V). We now report the synthesis of an acyclic nucleoside analogue (VI) as well as an acyclic nucleoside phosphonate analogue (VII) of the "fat" nucleoside V.

9-Benzyladenine (I) is a rare chemical often used by chemists, biochemists, as well as biophysical chemists doing research in the field of nucleic acids as a convenient heterocyclic base model for physicochemical comparison with adenosine. However, I is commercially unavailable, and the synthetic methods available from the literature are tedious and poor yielding. We have synthesized I from 5-amino-1-benzyl-4-cyanoimidazole (II) which, in turn, was synthesized from acyclic precursors, III, IV or V, using three different methods. We report herein all these methods, along with our recommendation for the best method in terms of both convenience and product yield to access both the imidazole precursor II and the target 9-benzyladenine (I).

Allylic alcohols undergo an efficient process of diastereoselective epoxidation by t-butyl hydroperoxide (TBHP) in n-hexane solution in the presence of catalytic amounts of mono- and dicyclopentadienyl titanium chlorides.

An efficient one pot synthesis of indoles from 2-bromo-arylacetonitriles is reported in this communication.

A new general two-steps synthesis of 5-functionalized 4-hydroxyhexahydropyrimidine-2-thiones/ones has been developed. This synthesis are based on preparation of the a-azido and a-tosyl(thio)ureas 2, 5 followed by reaction with enolates of a-functionally substituted ketones. All the obtained hydroxypyrimidines 8a-c are readily converted into the corresponding 5-functionalized 1,2,3,4-tetrahydrohydropyrimidine-2-thiones/ones 9a-c by heating in the presence of acids. Treatment of the 4-acylsubstituted 4-hydroxyhexahydropyrimidine-2-thiones/ones 8b with bases in acetonitrile gives the N-acyl-N'-(b-oxoalkyl)thioureas/ureas 10 in result of rearrangement including C(4)-C(5)-bond cleavage in 8b. Reaction of the (thio)ureides 10 and the 5-acylsubstituted 4-hydroxyhexahydropyrimidine-2-thiones/ones 8b with KOH in water leads to the 4-hydroxyhexahydropyrimidine-2-thiones/ones 11 without the acyl group at the C(5) position. Treatment of the ethyl 4-hydroxy-2-thioxohexahydropyrimidine-5-carboxylates 8a with bases in acetonitrile depending on the starting compounds structure yields either the 5,6-dihydro-2-thiouracils 12, 13 or the products of C(4)-C(5)-bond cleavage 14.

3-(4-Coumarinylmethylene)phthalides and 2-, or 3-(4-coumarinylethenyl)-4-chromones were prepared by condensation reaction. Beneficial effect of microwave irradiation on length of reaction time was investigated. Some subsequent reactions of these derivatives with nucleophiles are described. Nucleophile attack is studied by AM1 theoretical method.

Six-membered cyclic thioureas can be prepared by a convenient stereoselective method based on the reduction of readily available 4-hydroxy(or 4-alkoxy)hexahydropyrimidine-2-thiones or 1,2,3,4-tetrahydropyrimidine-2-thiones with NaBH4 - CF3COOH. Alternative method of the preparation of the target compounds includes reaction of 4-azido-, 4-acetoxy- or 4-arylsulfonylhexahydropyrimidine-2-thiones with NaBH4.