Nucleoside, XXXIII. Über die Synthese des 7‐Oxo‐8‐β‐ D ‐ribofuranosyl‐7,8‐dihydro‐lumazins und seines 6‐Methyl‐Derivates

Abstract

Die Synthese von 7-0xo-8-~-~-ribofuranosyl-7,8-dihydrolumazin (26) und seinem 6-MethylDerivat (28) kann durch Ribosidierung von 2,4-Bis(benzyloxy)- (18) (29) and its 6-methyl derivative (30), respectively, have been cleaved by catalytic hydrogenation on Pd/C to 25 and 27 and by ammonia in methanol to 26 and 28. Attempts for the synthesis of 26 starting from 6-amino-2,4-dimethoxy-S-nitropyrimidine (3) are also described, leading however only to the formation of 8-~-ribityl-(12) and 8-~-~-ribofuranosyl-2,4-dimethoxy-7-oxo-7,8-dihydropteridine (14), respectively.

Alkoxy‐5‐nitrosopyrimidines: Useful Building Block for the Generation of Biologically Active Compounds

“…These results were considered particularly relevant because there is no general procedure reported in the literature to prepare such polyalkoxy-5-nitrosopyrimidines. The only known precedent is the preparation of 4-amino-2,6-dimethoxy-5-nitrosopyrimidine (3; Figure 3), which has been prepared by direct nitrosation of the corresponding pyrimidine with sodium nitrite in aqueous acid solution [16] but in a poor 14 % yield, surely due to the propensity of the alkoxy groups to suffer hydrolysis under acidic conditions. [17] It is interesting to note that C(5)-nitrosation of 2,4,6-trimethoxypyrimidine was not achieved under any conditions.…”

Nucleosides. LXV. Synthesis of New Pteridine–N8–Nucleosides

“…A solution of 1-O-acetyl-2,3,5-tri-O-benzoyl-b-D-ribofuranose (31.28 g, 62 mmol) in CH 2 Cl 2 (400 ml) was added, followed by BF 3 -etherate (30 ml) and then the mixture stirred at r.t. for 24 h. The reaction solution was poured slowly into a saturated solution of NaHCO 3 (400 ml) (fuming!) [16] A solution of 9 (0.7.3 g, 1 mmol) in AcOEt (30 ml) was hydrogenated with H 2 in presence of Pd/C catalyst (0.25 g, 5%) in a shaking apparatus till the uptake of H 2 is finished after 2 days. It was stirred for 2 h and then kept in a separation funnel over night.…”

“…Found: C, 60.34; H, 4.35; N, 8.26.6-Methyl-8--D-ribofuranosyl-2(1H),4(3H),7(8H)-pteridinetrione (20) [16]. The product fraction was evaporated and the residue recrystallized from EtOH (121 ml) to give 0.372 g (58%) of mp.>186°C (decomp.).…”

Syntheses and properties of pterin ribonucleosides

“…Lumazine [2][3][4][5][6][7][8][9][10][11] and isopterin nucleosides 12 can be regarded as structural analogs of the pyrimidine nucleosides whereas the many pteridin-7-one N 8 -nucleosides [13][14][15][16][17][18][19][20][21][22][23] are structurally related to the purine nucleosides. The syntheses could be achieved either by a classical Hilbert-Johnson reaction 24 , the mercury salt method by Fox and Davoll 25 , the Hilbert-Johnson-Birkofer silyl procedure 26,27 or the silyl variant by Vorbrüggen 28 .…”

“…Ribosylations of 6,7-dimethylpterin (3) led with the halosugar 10 and HgO/HgBr 2 to 3-(2,3,5-tri-O-benzoyl-ß-Dribofuranosyl)-6,7-dimethylpterin (13) in 14% yield whereas the use of 11 and BF 3 -catalysis formed the N 1 -riboside (20) in 14% as the main reaction product besides 8% of the N 3 -isomer (13). The ribosylation reaction have also been extended to 6-methylpterin (4) yielding with 11 and BF 3 small amounts of the N 1 - (21) and N 3 -riboside (14), with 7-methyl-pterin (5) the N 3 -riboside ( (15) in 6% yield and with 7-tert.butylpterin (8) again a mixture of N 1 - (24) and N 3 -riboside (18). A highly unpleasant reaction was encountered with pterin (1) itself which led after a tedious isolation and purification process only to 10% yield of the 1-(2,3,5.tri-O-benzoyl-ß-Dribofuranosyl)pterin (25).…”