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Nowadays, DIC is the most widely used carbodiimide for solid-phase peptide synthesis, while EDC·HCl is mostly used only for solution-phase synthesis. In this paper, we report new coupling cocktails containing EDC·HCl in combination with potassium salts of OxymaPure and Oxyma-B (i.e., KOxyma and K-Oxyma-B, respectively). These reagent cocktails gave spectacular purity compared to DIC/classical N-hydroxylamine derivatives in the solid-phase peptide syn

High coupling yields and a racemization depression are observed using a combination of Oxyma and TFFH in solution- and solid-phase peptide synthesis.

Synthesized compounds are investigated for their monoamine oxidase (MAO) inhibitory activity.

The title oxyma sulfonate esters, NOXY and TOXY are more efficient alternatives to the benzotriazole sulfonate esters in terms of racemization suppression and coupling effectiveness.

5-Amino-7-(methylthio)furazano[3,4-d]pyrimidine (3) reacts readily with a variety of amines and hydroxylamines under mild conditions, with the introduction of an N-substituent at position 7. Using this reaction of (3) with 1-amino-4,4-diethoxy-3-pentanol (16), a synthesis of 6-acetyl-2,4-diamino-7,8-dihydro-9H-pyrimido[4,5-b][1,4]diazepine, (2), was achieved. Compound (2) is an amino analogue of a naturally occurring dihydrohomopterin (1).

Azidation of the chlor aldehyde 2, which was obtained from the 4-hydroxy-2-pyridone 1, afforded the ring-closed isoxazolopyridone 3. Thermolysis of the 3-acetyl-4-azido-2-pyridone 8, which was obtained from the corresponding 4-tosyloxy derivative 7, afforded isoxazolopyridine 9. Amination of the chloro aldehyde 2 yielded the pyrido[4,3-b]quinoline 11 instead of the 4-chloroazomethine 10.

N-Substituted aminouracils (1) react with malonates by cyclocondensation to 5-hydroxy-pyrido[2,3-d]pyrimidine-2,4,7-triones (2), which give with triethylorthoformate and aniline 6-(phenylaminomethylene)-pyrido[2,3-d]pyrimidine-tetraone (3). Halogenation of 2a-d (with R2 = Me) with phosphorylchloride leads to 5,7-dichloro-pyrido[2,3-d]pyrimidine-2,4-diones (4) by cleavage of the methyl group at N-8, whereas Vilsmeier reaction of 2 affords 5-chloro-6-formyl derivatives (6), which cyclize with arylamines to give benzo[b]pyrimido[4,5-h] 1,6-naphthyridines (9). Compounds 9 were obtained independently by amination of the tosylates 5 to the 5-arylamino compounds 8, and Vilsmeier formylation to yield 9.

2′-Deoxy-5′-0-(4,4′-dimethoxytrityl)-5-methyl-N 4-(1-pyrenylmethyl)-α-cytidine (5) was prepared by reaction of 1-pyrenylmethylamine with an appropriate protected 4-(l,2,4-triazolyl)-α-thymidine derivative 3 which was synthesized from 5-O-DMT protected α-thymidine 1. Aminolysis of 3 afforded 3′-O-acetyl-2′-deoxy-5′-O-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (8). Benzoylation of 8 and removal of acetyl afforded N 4-benzoyl-2-deoxy-5–0-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (10). The amidites of compounds 5and 10 were prepared and used in α-oligonucleotide synthesis. DNA three-way junction (TWJ) is stabilized when an α-ODN is used for targeting the dangling flanks of the stem in a DNA hairpin. Further stabilization of the TWJ is observed when 5 is inserted into the α-ODN at the junction region. Dedicated to Professor Gottfried Heinisch on the occasion of his 60th birthday.

From the methylene chloride extract of Ehretia ovalifolia leaves, a new flavone derivative named ovalifolin [3-(3-methyl-1-butenyl)-6-methoxy-5,7,4'-trihydroxy flavone] has been isolated and identified together with the known flavone aglycones apigenin, luteolin and the highly methoxylated flavanol araneosol. The structures of these metabolites have been established on the basis of chemical, chromatographic and spectral methods.

Reaction of 4‐hydroxy‐6‐methyl‐2(1H)‐pyridones 1a and 4‐hydroxy‐1,6‐dimethyl‐2(1H)‐pyridones 1b with diethyl malonates 2a–e leads to the formation of pyrano[3,2‐c]pyridines 4a–j. Degradation of 4a–i affords the corresponding ketones 6a–i. Condensation of ketones 6a–i with hydroxyl amine or phenyl hydrazine hydrochloride is described.

The unexpected parabanic acid derivatives 6a,b were obtained via unprecedented rearrangement of 5,5-diazidobarbituric acids 2a,b upon stirring in water at 50-60°C. Themolysis of diazides 2a,b in benzyl alcohol at 120–130°C afforded the tetrazole derivative 11 and/or benzyl allophanate 14.

This paper presents the synthesis of some novel acyclonucleosides containing 2-pyridinones and 2-hydroxyethoxymethyl, 2,3-dihydroxy-propyl side chain. The tosylate of these nucleosides analogues could be modified to azido derivatives. Also, acyclonucleosides with 1-ethoxymethyl, 1-benzyloxymethyl, 1-methylthiomethy 1 and 2-hydroxyethyl side chains have been investigated. The O-alkylated pyridine derivatives were obtained during most reactions.

was introduced in hyperten-sion therapy for more than 50 years, the mechanism of itsaction is still obscure [2]. The hydrazine group being areactive pharmacophore might actively react with any ofthe C=O of the biological receptors to exert its effect [3,4].It is notable that the so called N-acetyl derivative of

The naturally occurring dihydrohomopterin derivative 6-acetyl-2-amino-7,8-dihydro-9H-pyrimido-[4,5-b][1,4]diazepin-4(3H)-one (1) has been synthesised from 1-amino-4,4-diethoxypentan-3-ol (10) and 2-amino-6-chloro-5-nitropyrimidin-4(3H)-one (3). A novel tricyclic intermediate, 2,2a-dihydroxy-2-methyl-6-nitro-1,2,2a,3,4,5- hexahydro-1,5,8,8b-tetra-aza-acenaphthylen-7-one was isolated.