Sidney M. Hecht

N6-(Δ2-isopentenyl)adenosine: The regulatory effects of a cytokinin and modified nucleoside from tRNA on human lymphocytes

Abstract We have studied the effects of N 6 -(Δ 2 - isopentenyl)adenosine and related cytokinin analogs on the stimulation and inhibition of phytohemagglutinin-induced growth of human lymphocytes. We have found that N 6 -(Δ 2 - isopentenyl)adenosine exerts inhibitory effects on RNA synthesis, uridine transport and uridylate kinase synthesis. On the basis of the interaction of N 6 -(Δ 2 - isopentenyl)adenosine with cyclic AMP in this system, we propose that the observed stimulatory and inhibitory effects may be due to the involvement of N 6 -(Δ 2 - isopentenyl)adenosine in cyclic AMP metabolism.

A chemical synthesis of adenosine 5′-[γ-32P]triphosphate

Adenosine 5′-[γ-32P]triphosphate has been prepared from adenosine 5′-diphosphate by condensation of the phosphorimidazolidate of ADP with 32Pi. No purification of intermediates is required in this efficient synthesis, which is convenient for micro-scale conversions. This procedure permits the preparation of [γ-32P]ATP of high specific activity and should be applicable to the synthesis of many nucleoside triphosphates, including some which may not be accessible by enzymatic means.

In situ generation of diazomethane

A continuous method for the production of diazomethane comprising the steps of feeding: ```a diazomethane precursor, and ```a base into a reactor vessel where they react to generate diazomethane, and removing the resulting diazomethane as a gas.

Chemical modifications of transfer RNA species. Heavy atom derivatization of aminoacyl tRNA

Summary Specific heavy atom derivatization of valyl and arginyl tRNAs from E. coli has been effected by the use of the N-hydroxysuccinimide esters of certain carboxylic acids. The derivatized tRNAs have been separated from underivatized material and shown to be stable under the conditions required for crystallization.

Chemical modifications of transfer RNA species. Transfer RNA's terminating in 2′- and 3′-O-methyladenosine

Abstract The preparation of transfer RNAs terminating in 2′- and 3′- O -methyl-adenosine has been undertaken by a combination of chemical and enzymatic techniques to permit a determination of the mechanism of tRNA aminoacylation. Neither of the two synthetic tRNAs was aminoacylated substantially in the presence of aminoacyl-tRNA synthetases, consistent with the hypothesis that the aminoacyladenylate moiety exists in the form of a species with considerable orthoester character.

A concise synthesis of substituted 4-alkylaminopyrazolo[3,4-d]pyrimidines

4-Alkylamino-1-methylpyrazolo[3,4-d]pyrimidine-3-carbonitriles have been synthesised in 54–81% yields by condensation of N-substituted amides with 5-amino-1-methylpyrazole-3,4-dicarbonitrile via a Dimroth rearrangement in what is formally an anhydrous medium; the procedure thus permits the synthesis of pyrazolo[3,4-d]-pyrimidines with substituents sensitive to hydration.

Demethylation of 7-methylguanosine with lithium 2-methylpropane-2-thiolate

7-Methylguanosine, a component of transfer ribonucleic acid, is demethylated to guanosine, its presumed biochemical precursor, by a powerful new nucleophilic reagent, lithium 2-methylpropane-2-thiolate in hexamethylphosphoramide.