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Synthesis of [15N4] purine labeled cytokinine glycosides derived from zeatins and topolins containing a 9‐β‐d, 7‐β‐d‐glucopyranosyl, or 9‐β‐d‐ribofuranosyl group is described. These N6‐substituted adenine derivatives are intended as internal analytic standards for phytohormone analysis. All labeled compounds were prepared from 6‐chloro[15N4]purine (1). The equilibrium reaction of 1 with acetobromo‐α‐d‐glucose gave isomeric 7‐β‐d (3) and 9‐β‐d (4) chloro glucosyl precursors, which were treated with the corresponding amines to get desired labeled cytokinin 7‐β‐d (6) and 9‐β‐d (5) glucopyranosides. Cytokinins containing 9‐β‐d‐ribofuranosyl group (8) were obtained by direct enzymatic transglycosylation reaction of cytokinins (7) prepared from 6‐chloro[15N4] purine (1). Synthesis and characterization of some [15N4] purine labeled cytokinin glycosides derived from zeatins and topolins containing 9‐β‐d, 7‐β‐d‐glucopyranosyl, or 9‐β‐d‐ribofuranosyl group with using chemical and enzymatic approaches is described. [ABSTRACT FROM AUTHOR]

A new N 7 direct regioselective method allowing the introduction of tert -alkyl groups into appropriate 6-substituted purine derivatives is developed. This method is based on a reaction of N -trimethylsilylated purines with a tert -alkyl halide using SnCl 4 as a catalyst. In this work, we study the structure and optimal reaction conditions leading to the N 7 isomer and in some cases also to the N 9 isomer. The main goal is devoted to preparing 7-( tert -butyl)-6-chloropurine as a suitable compound for other purine transformations. The stability of the tert -butyl group at the N 7 position is tested for classic model reactions, leading to the preparation of new 6,7-disubstituted purine derivatives, which is also interesting from the point of view of possible biological activity., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

6-Chloropurine and 2,6-dichloropurine were regioselectively glycosylated at position 7 to give the corresponding peracetylated N 7 -nucleosides, which can be suitable for other purine transformations. In this work, we study the distribution of N 7 / N 9 -isomers produced via the Vorbrüggen method under different conditions, using an N -trimethylsilylated purine derivative and SnCl 4 or TiCl 4 as a catalyst. The main effort is devoted to reversing the disadvantageous predominant selectivity of most glycosylation reactions at the N 9 position and thus to determining conditions that maximize the regioselectivity of glycosylation toward the desired N 7 -isomer.

Synthesis of [ 15 N 4 ] purine labeled cytokinine glycosides derived from zeatins and topolins containing a 9-β-d, 7-β-d-glucopyranosyl, or 9-β-d-ribofuranosyl group is described. These N 6 -substituted adenine derivatives are intended as internal analytic standards for phytohormone analysis. All labeled compounds were prepared from 6-chloro[ 15 N 4 ]purine (1). The equilibrium reaction of 1 with acetobromo-α-d-glucose gave isomeric 7-β-d (3) and 9-β-d (4) chloro glucosyl precursors, which were treated with the corresponding amines to get desired labeled cytokinin 7-β-d (6) and 9-β-d (5) glucopyranosides. Cytokinins containing 9-β-d-ribofuranosyl group (8) were obtained by direct enzymatic transglycosylation reaction of cytokinins (7) prepared from 6-chloro[ 15 N 4 ] purine (1)., (© 2018 John Wiley & Sons, Ltd.)