Nitration and bromination of isocytosine-6-acetic acid. Corrections

Abstract

oped with petroleum ether (bp 30-6O0)-ether (2:1)] to give two fractions in addition to additional pure 2d (total recovery 52%).The first of these was a mixture (nmr)3 of syn alcohol Id (-10% yield by nmr) and anti formate 2g (30% yield) which have nearly identical Rf values. The anti formate, which was unknown, was purified by recrystallization of this mixture from chloroformpetroleum ether (bp 60-90"): nmr (CDC13) 6 8.19 (1, s, 02CH), 8.19-7.58 (4, m, aromatic H), 6.23 (1, X portion of ABX, JAX + J B X = 16 Hz, q, CHOzCH), 3.75-0 (broad m, 18, bridge CH2).Anal. Calcd for C20H24NOzC1: C, 69.45; H, 6.99; N, 4.05.Found: C, 69.68; H, 7.01; N, 4.04. The mother liquor from this recrystallization contained (tlc and nmr) syn alcohol ld, anti formate Id, and trace amounts of another material assumed to be syn formatedg,The other fraction (5.5 mg, 6% yie1d)was reduced pyridinophane IC (mp and mmp4b of picrate 173-174').Thermal Stability of Syn and Anti Bromides (lb and 2b). A.A solution of syn l b (50.5 mg, 0.133 mmol) in xylene (ACS grade, 0.5 ml) was heated at the reflux temperature under nitrogen for 220 hr. Xylene was removed (in vacuo) from the brown, tarry mixture; the residue showed (nmr) unchanged 2a (6 6.06) and no epimer 2b (6 5.42). The sample was dissolved in chloroform and washed with dilute sodium bicarbonate and the product was recrystallized from petroleum ether to give 41.6 mg (82.3% recovery) of 2a, m p 141-142", mmp 143-144" with material melting at B. A sample of anti 2b (65.8 mg, 0.173 mmol) was treated in xylene as described above. The nmr spectrum of the crude product showed no 2b (6 5.42) or 2a (6 6.06) and was quite similar to that of IC. The product was decolorized as above and purified by preparative tlc [silica gel, petroleum ether-ether (3:1)] to give 26 mg (50% yield) of IC (mp and mmp 78-79"). ., 35,3775 (1970).Aikylsuifonates normally undergo carbon-oxygen scission under these conditions: the authors are unaware of related acid-catalyzed S-0 bond cleavage. 2-and 4-methyipyridines undergo hydrogen-deuterium interchange on the methyl group, presumably through a carbanion intermediate, under rather mild conditions: cf. K. Schofieid, "Hetero-Aromatic Nitrogen Compounds," Butterworths, London, 1967, pp 324-327, and references cited therein. Sulfur-oxygen bond cleavage of aikylsuifonates by base is uncommon, since substitution or elimination at carbon generally occurs. However, aryisuifonates readily undergo S-0 bond cleavage by nucleophiles: cf. W. D. Ciosson and P. Wriede, J. Amer. Chem. Soc., 88,1581 (1966).

Improved Syntheses of 3H,5H-Pyrrolo[3,2-d]pyrimidines

“…After the report of a 10-step procedure to synthesize 9-deazaguanine ( 1 ) in 0.86% efficiency, and of a further method 7 that could not be reproduced by others, , the latter workers developed a five-step, 20% efficient approach starting from 2-amino-6-methyl-5-nitropyrimidin-4-one ( 5 ) which is readily made by the nitration of the commercially available 2-amino-6-methylpyrimidin-4-one . Their reaction of compound 5 with DMF dimethyl acetal in CH 2 Cl 2 gave the imine 6 in excellent yield, and this was N-protected using pivaloyloxymethyl chloride to give compound 7 (60%).…”