Add time:08/26/2019         Source:sciencedirect.com

Raney nickel-2H2O exchange reaction on an epimeric mixture of methyl α/β-D-ribofuranoside [α/β = ∼3:10]1 produced methyl 1#,2,3,4#,5,5′-2H6-α/β-ribofuranoside 2 [97 atom % 2H at C2, C3, C5/5′; ∼85 atom % 2H at C4 (C4#); ∼20 atom % 2H at C1(C1#)] which was obtained in 60 – 80 % yield along with epimeric xylo and arabino by-products. Toluoylation of the crude 2 in dry pyridine and a careful separation on a column of silica gel gave pure 1-O-methyl-2,3,5-tri-O-(4-toluoyl)-α/β-D-1#,2,3,4#,5,5′-2H6-ribofuranoside 4 (48%). Conversion of 4 to 1-O-acetyl-2,3,5-tri-O-toluoyl-α/β-D-1#,2,3,4#,5,5′-2H6-ribofuranoside 6 (82%) provided the crucial building block for the synthesis of deuterionucleosides for RNA or DNA synthesis. Compound 6 was then condensed with silylateduracil, N4-benzoylcytosine, N6-benzoyladenine, N2-acetyl-O6-diphenylcarbamoylguanine and thymine in anhydrous solvent using trimethylsilyl trifluoromethanesulfonate to give the corresponding isomerically pure 1′#,2′,3′,4′#,5′,5″-2H6-ribonucleoside derivatives 7, 8, 9, 10, 11 in 75, 85, 60, 73 and 91% yields, respectively. 1′#,2′,3′,4′#,5′,5″-2H6-ribonucleosides 13 – 16 were converted in high yields to the corresponding 1′#,2′,2″,3′,4′#,5′,5″-2H7-2′-deoxynucleosides 41 – 44 in the following manner: 3′,5′-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl (TPDS))-1′#,2′,3′,4#′,5′,5″-2H6-nucleosides 29 – 32 were converted to the corresponding 2′-O-phenoxythiocarbonyl derivatives 33 – 36, which were deoxygenated by tri-n-butyltin deuteride to give 1′#,2′,2″,3′,4′#,5′,5″-2H7-2′-deoxynucleosides 37 – 40 and subsequently deprotected to give 41 – 44. Pure 1′#,2′,3′,4′#,5′,5″-2H6-ribonucleoside derivatives 12 – 15, 1′#,2′,2″,3′,4′#,5′,5″-2H7-2′-deoxynucleoside blocks 41 – 44 and their natural-abundance counterparts were then used to assemble partially deuterated ribonucleotide-dimers (* indicates deuterated moiety): UpA* 77, CpG* 78, ApU* 79, GpC* 80, partially deuterated 2′-deoxyribonucleotide-dimers d(TpA*) 93, d(ApT*) 95, d(GpC*) 96 and partially deuterated 2,5A core (A*2′p5′A2′p5′A*) (109). These nine partially deuterated oligonucleotides were subsequently compared with their corresponding natural-abundance counterparts by 500 MHz 1H-NMR spectroscopy to evaluate the actual NMR simplifications achieved in the non-deuterated part (1H-NMR window) as a result of specific deuterium incorporation. Detailed 1D 1H-NMR (500 MHz), 2D correlation spectra (DQF-COSY & TOCSY), T1 measurements for 1H-, 13C- and INEPT 13C-NMR spectra have been presented and discussed to assess the utility of stereospecific deuterium incorporation create the 1H- or 13C-NMR window.

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