Photochemical intramolecular nitrene insertion of 6‐azidouridine derivatives

Abstract

A highly efficient intramolecular nitrene insertion was observed upon irradiation of 6‐azidouridine derivatives. The N6,2′‐cyclo structure of the product was determined unequivocally by X‐ray crystallography.

Preparation of Cyclonucleosides

“…123 An iodine/iodic acid mixture in glacial acetic acid afforded the expected 5-iodo-2′-deoxycitidine (177) together with 5,5-diiodo-5,6dihydro-6,5′-O-anhydro-2′-deoxyuridine (178) 124 as the minor byproduct. Alkaline treatment of 178 gave 5-iodo-6,5′-Oanhydro-2′-deoxyuridine (179); further hydrogenation of 179 gave 6,5′-O-anhydro-2′-deoxyuridine (180), which could be iodinated back to 179 by a mixture of iodine/iodic acid (Scheme 40). Recently, Guo et al 125 reported a novel method for the synthesis of 179 based on molecular iodine in ammonia-water under mild conditions without any other aprotic solvent.…”

“…A different approach leading to a 6,2′-N-bridge was investigated by Miyasaka et al (Scheme 73). 179 When 6-azido-2′,3′-O-isopropylidene-5′-O-(methoxymethyl)uridine (316) was irradiated with a 250 W high-pressure mercury lamp equipped with a Pyrex filter in dry THF, the photochemical intramolecular insertion of the 6-azido group led to the 6,2′-N-bridged cyclonucleoside 317. Similar photochemical reactions were carried out for the N 3 -methyl and 5-methyl derivatives of 316, giving the respective cyclized products with 60% and 86% yield.…”

“…A different approach leading to a 6,2′- N -bridge was investigated by Miyasaka et al (Scheme ) . When 6-azido-2′,3′- O -isopropylidene-5′- O -(methoxymethyl)uridine ( 316 ) was irradiated with a 250 W high-pressure mercury lamp equipped with a Pyrex filter in dry THF, the photochemical intramolecular insertion of the 6-azido group led to the 6,2′- N -bridged cyclonucleoside 317 .…”

Synthesis and Photochemical Behavior of the Tetrazolo Tautomer of 2-Azido-4-pyrimidinone-2′-deoxyriboside

“…In addition, their use in the preparation of fluorescent probes by click chemistry has recently been reported . 6-Azidonucleosides initially prepared to be photochemical tools are employed as synthetic intermediates. , Surprisingly, the synthesis of 2-azidonucleosides has never been reported, even though the synthesis of 2-azido-4-pyrimidinones is known …”