Synthesis of 6-substituted purin-2-ones with potential cytokinin activity

Abstract

6-Substituted purin-2-ones have been prepared by completely regioselective addition of Grignard reagents to an N-protected purin-2-one followed by rearomatisation and deprotection. The target compounds may be regarded as analogues of the potent cytokinins trans-zeatin and benzylaminopurine (BAP), and most of the BAP analogues did induce increased weight growth in radish cotyledons. N-Protected (E)-6-styrylpurin-2-one underwent head to tail [2+2] dimerisation to the 1α,2α,3β,4β-substituted cyclobutane 15, when exposed to ordinary daylight. When irradiated with UV-light, the trans-compound isomerised to the corresponding cis-isomer. The structure of compound 15 was determined by single crystal X-ray diffraction methods at 150 K.