Method for Preparing New Flavin Derivatives:  Synthesis of Flavin−Thymine Nucleotides and Flavin−Oligonucleotide Adducts

Abstract

In order to link to the 5′-end of oligonucleotides the flavin analogs 9a,b possessing only one terminal hydroxy group on the side chain, the phosphoramidite and the H-phosphonate coupling methods were developed. Surprisingly, after reaction of compounds 9a,b with 2-cyanoethyl N,N-diisopropylchlorophosphoramidite, the flavin phosphoramidates 11a,b were isolated instead of the expected phosphoramidite derivatives 10a,b. A very efficient photooxidation process occurred probably during the isolation of the products. From the prepared flavin H-phosphonates 12a,b, flavin-thymine nucleotides and flavin-oligonucleotide adducts were synthesized for the first time. The versatility of the method was demonstrated in the oxidation step with the synthesis of the flavin-thymine nucleotides 15-17 possessing a phosphodiester, a phosphorothioate, and a methyl phosphate linkage, respectively. This method is of general interest with regard to the extensive research developed for preparing flavin analogs and modified oligonucleotides possessing interesting biological or/and catalytic properties.

Excess Electron Transfer in Flavin-Capped DNA-Hairpins

“…[28Ϫ31] This complicated protocol is required because flavin phosphoramidites are efficiently oxidized under aerobic conditions. [32,33] A complete H-phosphonate protocol is also not applicable because only Hphosphonates with standard protecting groups are commercially available. These require harsh deprotection conditions, which were found to be incompatible with the baselabile flavin molecule.…”

User-friendly Synthesis and Photoirradiation of a Flavin-linked Oligomer

“…Oligonucleotides containing ‰avin have been previously synthesized, but the synthetic methods required complex and tedious steps more complicated than the method described in this report (7)(8)(9)(10). The presented synthetic method for ‰avin-phosphoramidite has only three steps and the reaction conditions are milder, using sodium periodate instead of sulfuric acid and periodic acid (11), and pH adjustment was not required.…”

“…As ‰avin is an oxidant, the phosphoramidite which has a trivalent phosphorus is slowly oxidized (9). Therefore, ‰avin phosphoramidite was used without puriˆca-tion and the ‰avin-phosphoramidite should be generated from 2 before use.…”

“…These facts raise the intriguing possibility that a ‰avin-linked oligomer could be used as tool for investigation of long-range hole transfer as well as excess electron transfer. Although the syntheses of ‰avin-linked oligomers have been reported, the synthesis of such oligomers requires complex and tedious steps (7)(8)(9)(10). Here, we report the simple, userfriendly and practical synthesis of a ‰avin-linked oligomer and its application in the remote oxidation of 8-oxoG in a DNA duplex via a hole-transfer mechanism.…”

A Reagentless Biosensor for the Amperometric Determination of NADH

“…The flavin-pyrrole conjugate 1 was synthesized from the pyrrole derivative 3 (Scheme 2) and the flavin H-phosphonate 4 (Scheme 2) prepared according to procedures described previously [43,44]: to a solution of compound 4 (57 mg, 0.11 mmol) in dry pyridine (3 mL) were added, under argon in the dark, a solution of 1-adamantanecarboxylic acid chloride (130 mg, 0.66 mmol) in pyridine (5 mL) and then a solution of the pyrrole derivative 3 (40 mg, 0.32 mmol) in pyridine (2 mL). The mixture was stirred for 24 h, and then water (5 mL) was added.…”