Antineoplastic activity of fused nitrogen-phosphorus heterocycles and derived phosphonates

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

A series of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines was synthesized for the first time by the reactions of chloroethynylphosphonates with unsubstituted and 5(6)-substituted 2-thiouracils. The reaction of chloroethynylphosphonates with 6-substituted 2-thiouracils bearing electron-donor groups (CH₃, Ph) proceeded with high regioselectivity involving the cyclization through the N³-nitrogen atom to form new 3-phosphonylated thiazolo[3,2-a]-5-oxopyrimidines with good yield. In the case of unsubstituted and 5-methyl-2-thiouracils, cyclization occurred predominantly through the N¹ atom and partially via the N³-nitrogen atom to form a mixture of the corresponding thiazolo[3,2-a]-7- and 5-oxopyrimidines. A dramatic change in the reaction regioselectivity was observed in the case of 6-trifluoromethyl-2-thiouracil that afforded 2- and 3-phosphonylated 5-oxothiazolopyrimidines in a 1:1 ratio.

Mg(OCH3)2-mediated one-pot synthesis of α-aminophosphonate derivatives of cytosine under mild conditions

An efficient one-pot synthesis of α-aminophosphonates of cytosine with aldehydes, diisopropylH-phosphite, and cytosine with the help of simple magnesium methanolate was discovered. α-Aminophosphonates of cytosine were obtained in good yields under mild conditions. The reaction tolerates both electron-donating and electron-withdrawing substituents of aromatic and aliphatic aldehydes.