Modifications. Representative modifications of the resulting methyl sulfones were undertaken to obtain various functionalized building blocks (compounds with one or two functional groups) for use in medicinal chemistry (Scheme 4A). Saponification of the ester group in products 28, 32, 33, 35 and 40 gave carboxylic acids "a". Acidic cleavage of N-Boc group in 18-21 gave amines "b". The reaction of pyrimidone 14 and pyridines 34, 35 with POCl3 afforded compounds with active chlorine atoms "c". Alkylation of compound 15 with methyl iodide gave the previously inaccessible product 16. Finally, treatment of compound 50 with hydrobromic acid gave pyridone 50d, and its subsequent reaction with POCl3 afforded chloride 50e.