A Convenient Method for the Synthesis of Stable α‐Fluoro Enamines of Nucleobases

Abstract

Treatment of a whole set of nucleic acid bases and related derivatives 4, 9 and 10 with electron‐deficient hexafluoropropene or 1,1,3,3,3‐pentafluoropropene in the presence of sodium hydride gave the corresponding N1 and N9 stable fluorinated enamines with high regioselectivity. This alkylation is a result of a Michael type addition–elimination process and gave the desired products 2a–10a and 2b–10b as E/Z mixtures. Unexpectedly, treatment of 2b with tert‐butyllithium and subsequently with [D4]methanol gave different results for E and Z stereoisomers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A convenient synthesis of fluorinated vinyl ethers derived from di-O-isopropylidenehexofuranose and O-isopropylidenepentofuranose

“…Wó jtowicz-Rajchel et al have been using NaH to generate corresponding sodium salts of nucleic bases [19]. However, in our case, application of NaH has not given the expected results.…”

“…The yields of reaction products were conveniently evaluated by 19 F NMR in CDCl 3 using mfluorotoluene as internal standard. Gas chromatography was performed using Varian 4000GC/MS equipped with capillary column Varian VF-5ms.…”

“…Hv 00 = 10.7 Hz, J Hv-Hv 0 = 3.0 Hz, J Hv-5 = 1.4 Hz, Hv), 5.73 (1H, dd, J Hv 0 -Hv 00 = 4.6 Hz, J Hv 0 -Hv = 3.1 Hz, Hv 0 ), 5.87 (1H, dd, J Hv 00 -Hv = 10.0 Hz, J Hv 00 -Hv 0 = 3.5 Hz, Hv 00 ), 6.03 (1H, d, J 1-2 = 3.7 Hz, H-1), 6.85 (1H, dq, J H-F = 9.1 Hz, J H-CF3 = 1.2 Hz, H b ) ppm. 13 C NMR: d 26.3, 26.8, 57.3, 80.6, 82.1, 83.8, 84.1, 105.4, 112.09, 119.9 (dq, J = 269.0, 34.8 Hz, CF 3 ), 120.05, 132.13, 133.01 (m), 133.02 (dq, J = 252.2, 39.7 Hz, = C b ) ppm 19. F NMR: d À180.92 (1F, dq, J F-CF3 = 11.9 Hz, J F-H = 9.2 Hz, F),…”

The nitrogen inversion in fused isoxazolidinyl derivatives of substituted uracil: synthesis, NMR and computational analysis

“…In the course of our work on fluorovinyl derivatives of nucleic acid bases and their cycloaddition reactions with nitrones [32][33][34], we decided to synthesize a series of isoxazolidinyl derivatives of 5-fluorouracil in 1,3-dipolar cycloaddition of N-fluorovinyl-5-fluorouracil with nitrones. Unexpectedly, we obtained exclusively, without any competitive reaction, the cycloaddition product not to exocyclic, but to endocyclic double bond with the formation of fused ring.…”

Synthesis and applications of fluorinated nucleoside analogues

“…In 2008 Wó jtowicz and Koroniak prepared stable a-fluoroenamines of nucleobases [139]. All known a-fluoroenamines readily react with water to give the corresponding amides and hydrogen fluoride in an addition-elimination process [140].…”