George H. Milne

The synthesis of α- and β-2′-deoxyselenoguanosine

The α- and β-anomers of 2′-deoxy-6-selenoguanosine have been prepared from 2-acetamido-6-chloro-9-(2-deoxy-3,5-di-O-p-toluoyl-α- and β-d-erythro-pentofuranosyl) purine. The structure of the individual anomers has been firmly established using ultraviolet and PMR spectroscopy. The potential anticancer activity of both anomers is discussed.

Purine nucleosides. Part XXXII. Synthesis and reactivity of 6-alkyl-seleno-9-(β-D-ribofuranosyl)purines

The alkylation of 6-selenoxo-9-(β-D-ribofuranosyl)purine with several alkyl halides under basic conditions has furnished the corresponding 6-alkylseleno-9-(β-D-ribofuranosyl)purines. A ready removal of the 6-methylseleno-group from the 6-methylseleno-derivative (3) with Raney nickel under mild conditions has furnished an almost quantitative yield of nebularine. Treatment of the 6-benzylseleno-derivative (4) with nucleophilic reagents has demonstrated the ease of displacement of the alkylseleno-group.

Pyrazolopyrimidine nucleosides. Part IV. Synthesis and chemical reactivity of the C-nucleoside selenoformycin B and derivatives

The synthesis of 7-selenoxo-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (2)(selenoformycin B) has been accomplished by a nucleophilic displacement of the chloro-group from 7-chloro-3-(β-D-ribofuranosyl)pyrazolo-[4,3-d]pyrimidine (1) with selenourea in ethanol at reflux temperature. Alkylation of (2) has furnished several 7-alkylseIeno-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidines. A study on the relative reactivity of certain 7-substituted 3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidines and the corresponding 6-substituted 9-(β-D-ribofuranosyl)purines toward nucleophilic displacement is discussed. 7-Methoxy-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (5) and the nebularine derivative 3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (3) have also been prepared. The stability of (2) towards basic and approximate physiological pH conditions is discussed.