Tozo Fujii

Cytokinins: Structure/activity relationships☆

Abstract Sixty-nine compounds, mostly purine derivatives and closely related substances, were tested for promotion of growth and regulation of organ formation in the tobacco bioassay to determine relationships between chemical structure and cytokinin activity. Forty-three substances were synthesized in this study, and 13 of these were reported for the first time. N 6 -Alkyladenines (I) varied in activity over a wide concentration range depending on the length of the alkyl chain. Starting with adenine, detectable at ⩾200 μM, activity increased with the chain length to an optimum for 6-pentylaminopurine detectable at ca. 0–001 μM, and then decreased to reach a barely detectable level for 6-decylaminopurine. The result of the incorporation of polar groups in the side chain was not necessarily reduction in activity. One hydroxyl group, as in zeatin (Id), improved the activity of 6-(γ,γ-dimethylallylamino)purine (Ib) if it affected it at all; two hydroxyl groups, as in 6-(2,3-dihydroxy-3-methylbutylamino)purine strongly reduced activity. Comparisons of 6-isoamylaminopurine with 6-(γ,γ-dimethylallylamino)purine and of other closely related pairs of compounds showed that a double bond in the side chain greatly increased cytokinin activity. Adenine derivatives with cyclic substituents in the N 6 -position (benzyl-Ic), cyclohexyl-, etc.) showed the same general range of activity, potentiation by unsaturation, and variation in activity with substituent size, etc. as did the alkyl derivatives. Heteroatoms in or on the substituent groups decreased activity (in the case of N or Cl) or had little effect (S for O in furfuryl). Of the mono-substituted adenines only the N 6 -derivatives definitely possessed cytokinin activity. The 1-(III), 3-(II), or 9-substituted adenines probably are inactive but could be activated by conversion to the N 6 -isomers. Except for slight activity in tests of high concentrations, which could be ascribed to contaminants, 7-substituted adenines were completely inactive. Modification in the adenine moiety lowered the cytokinin activity, often by 95 per cent or more. Substitution of N for the 8-C atom in kinetin and in 6-benzylaminopurine or S for the 6-amino N atom in 6-(γ,γ-dimethylallylamino)purine did not eliminate but drastically reduced activity in the tobacco bioassay. Elimination of the 6-amino group without substituting another group completely removed activity; thus, the purine derivatives, 1-benzylpurine and 1-(γ,γ-dimethylallyl)purine, were inactive in tests where the 1-adenine derivatives could be activated to give a positive response. Addition of a second substituent on the 1-or 3-position of N 6 -substituted adenines drastically reduced or eliminated cytokinin activity. It is suggested that the 1-position and possibly also the 3-position must be free. A second substituent in the N 6 -, 7-, or 9-position of N 6 -substituted adenine derivatives lowered but did not eliminate activity. Also, the disubstituted 1-adenine derivatives, 1,9-dibenzyladenine and 1,7-dibenzyladenine were active, presumably after rearrangement to the corresponding N 6 -substituted isomers.

Alternative Syntheses of Azepinomycin

Synthese du compose du titre a partir de lamide de lacide formamido-5 O-alkyl alkyl-1 imidazolecarbohydroximique-4 via des alkyl-1 hydroxy-6 hexahydro-3,4,5,6,7,8 imidazo [4,5-e] diazepine-1,4one-8

Synthesis and absolute configuration of the green alga cytokinin 2-hydroxy-1'-methylzeatin

The correctness of the gross structure of the marine green alga cytokinin 2-hydroxy-1-methylzeatin (1) has been confirmed as a result of the chiral syntheses of (1R)-1 and (1S)-1. An indirect comparison of the cytokinin activity of the natural cytokinin with those of the synthetic enantiomers suggests that the R configuration may be assigned to the natural one unless it would be racemic

A Unique Transformation of 5-Amino-N'-methoxyimidazole-4-carboxamidines by Diazotization: Synthesis of the 5-Azido Analogue of ACIA Riboside

Diazotization of 1-substituted 5-amino-N-methoxyimidazole-4-carboxamidines (I) was found to give the 5-azidoimidazole-4-carbonitriles II through the 1-methoxy-2-azaadenine intermediates IV. The product IIb from the riboside Ib was utilized for the synthesis of 5-azido-1-β-D-ribofuranosylimidazole-4-carboxamide (Vb), a novel AICA riboside analogue

Synthesis, ring opening, and glycosidic bond cleavage of 3-methyl-2′-deoxyadenosine

Methylation of N′-benzyloxy-1-(2-deoxy-β-D-ribofuranosyl)-5-formamidoimidazole-4-carboxamidine (2a) followed by hydrogenolysis of the N′-benzyloxy-group and cyclization produced the hitherto unknown 3-methyl-2′-deoxyadenosine (5a), which was readily hydrolysed to 3-methyladenine (6) in H2)O at pH ⩽7·0 and to (6) and the imidazole-(2-deoxy)riboside (4a) at pH 8·98.

A synthetic approach to the marine sponge alkaloids agelasimine A and agelasimine B

Syntheses of 7-benzyl-N 6 ,3-dimethyladenine (1b) and 7-benzyl-1,2-dihydro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine A (1a) and agelasimine B (2a), respectively, have been achieved via four-step routes starting from 3-methyladenine (7). The key steps involved are regioselective methylations of 7-benzyl-3-methyladenine (9) and 7-benzyl-1,2-dihydro-3-methyladenine (11)

Synthesis and hydrolysis of 3-methyladenosine

Methylation of N′-benzyloxy-5-formamido-1-β-D-ribofuranosylimidazole-4-carboxamidine (1) followed by hydrogenolysis of the N′-benzyloxy group and cyclization gave the hitherto unknown 3-methyladenosine (4), which was easily hydrolysed to 3-methyladenine (6) in 0·1 N aq. HCl and to the imidazole ribosides (3) and (5) under basic conditions.

Model Experiments for Acetylation of the Marine Sponge Purines Agelasimine-A and Agelasimine-B

Reactions of 7-benzyl-N 6 ,3-dimethyladenine (1b) and 7-benzyl-1,2-dihy- dro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine-A (1a) and agelasimine-B (2a), with acetic anhy- dride in pyridine have been studied. The product from (1b) was the imidazole derivative (6b), whose structure was determined by an X-ray crystallographic analysis. The product from (2b) was the N 6 -acetyl derivative (4b). On treatment with boiling H 2 O, (4b) gave 7-benzyl- 2,3-dimethylhypoxanthine (5b) and a compound presumed to be (11)

Structure and absolute configuration of the Ochrosia alkaloid ochromianine: syntheses of (±)- and (−)-ochromianine

Syntheses a partir des (I)- et (+)-6-ethoxy-3-ethyl-2,3,4,5-tetrahydro pyridine-4-acetates dethyle et de 3-chloroacetyl-6-methoxyindole

Synthesis of 3,9-dimethyl- and 3-methyl-9-ethyl-adenine via N′-alkoxy-1-alkyl-5-formamidoimidazole-4-carboxamidine

3,9-Dimethyl- and 3-methyl-9-ethyl-adenine have been synthesized from N′-alkoxy-1-alkyl-5-formamidoimidazole-4-carboxamidine (II) by reduction with LiAIH4 followed by cyclisation with ethyl orthoformate and removal of the alkoxy-group by catalytic hydrogenolysis.