title: Analogues of formycins A and B: synthesis and some properties of methyl derivatives of 7-amino and 7-keto pyrazolo(4,3-d)pyrimidines.
abstract: Starting from the synthesis of 3-propyl-7-ketopyrazolo(4,3-d)pyrimidine (a formal analogue of formycin B), this was converted to the 7-thio derivative, which was aminated to give 3-propyl-7-aminopyrazolo(4,3-d(pyrimidine (a formal analogue of formycin A) and its methylamino derivatives. With the aid of different methylating agents, all four possible ring N-mono-methyl derivatives of the foregoing have been synthesized. Dimethyl derivatives were prepared on a small scale and identified by cross-methylation reactions, spectral properties and chromatographic behaviour. The basic physico-chemical properties of all the foregoing are described, including ultraviolet absorption spectra, spectrophotometrically determined pK values, and the 1H chemical shifts in aqueous medium and/or dimthjyl sulphoxide. The spectral properties of the various analogues indicate that the N6-methyl derivatives exist predominantly in the imino form, in contrast to the predominant amino form of the corresponding analogue from the adenine series, N1-methyladenine, but similar to the fixed imino form of N1-methyl-9-substituted adenines.
mesh_terms: D000586:Amination; D000903:Antibiotics, Antineoplastic / Q000138:chemical synthesis*; D055598:Chemical Phenomena; D002621:Chemistry; D005573:Formycins / Q000138:chemical synthesis*; D008745:Methylation; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000903:Antibiotics, Antineoplastic; D005573:Formycins; D011743:Pyrimidines; C027180:7-ketopyrazolo(4,3-d)pyrimidine; C027179:7-aminopyrazolo(4,3-d)pyrimidine