Nucleoside, XI. Synthese von Isoxanthopterin‐ N‐ 8‐β‐ D ‐ribofuranosidein strukturanaloges Nucleosid des Guanosins

Abstract

Eingegangen a m 1. MarL 1973 Die Ribosidierung einer Reihe von 2-Amirio-4-dlkoxy-7-oxo-7,8-dihydropteridinen 4 -7, 9, 10 und des Isoxanthopterins (11) nach der ,,Silyl-Methode" wird hev,hriehen. Es entstehen dls Hauptreaktionsprodukte 7-0x0-7,8-dihydropteridin-N-8-~-u-riboside, wdhrend die entsprechendeii 7-Ribosyloxy-pteridine 37-41 nur in untergeordnetem MaBe gehildet uerden.Danebeii lal3t sich dcr Nachwcis fur die Fxistenz von N2,S-Diribosiden erbringen und im Falle von 11 sogar ein Triribosid der vermutlichen Struktur 36 in Substanz isolicrcn Dic Strukturen dcr ndLh Lhromatograpliischen Verfahren isolierten ncucii Suhstm7cn wcrdcn durch UV-, NM R und CD-Spektren beatimmt tind gesichert. Nucleosidcs, Xl1) Synthesis of Isoxant~opterin-N-8-P-o-riboFuranoside -A Structural Analog of the Nucleo-

Pteridines. Part LXXXV. Chemical synthesis of deoxysepiapterin and 6‐acylpteridines by acyl radical substitution reactions

“…The product fraction is evaporated and the residue recrystailized from 120 ml of EtOH/benzene 2:1 to yield 0. -7-(methylthio)-6-(3-phenylpropionyl)pteridine (26). To a soln.…”

“…To a mixture of 100 ml of POC1, and 5.0 g of KCI are added 4.89 g (0.05 mol) of 4 [26], and then the flask is put in a hot oil bath (140"). After heating for 12 min with stirring, the mixture is cooled with ice, the excess of POCI, evaporated in vacuum, and the residue treated with 100 g of ice and 150 ml of CHC1,.…”

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).…”

Pteridines. Part XCVII. Synthesis and properties of 6‐thioxanthopterin and 7‐thioisoxanthopterin

“…thopterin (13) from 2-amino-4-(pentyloxy)pteridine (3; Scheme I ) . This starting material was obtained by a Gabriel-Zsuy reaction [ 171 between 2,5,6-triamino-4-(pentyloxy)pyrimidine [18] and glyoxal in 69% yield. Oxidation of 3 in CF,COOH with 30% H,O, proceeded analogously to pterin [ 191 and afforded 2-amino-4-(pentyloxy)pteridine N(8) -oxide (4) in 42 YO yield accompanied by the formation of 18 70 of pterin N(8) -oxide 6 as a by-product.…”