146.0, 140.2, 128.0, 124.5, 119.3, 113.6, 89.4, 84.4, 83.0, 81.6, 44.6, 27.0, 25.2. HRMS (ESI+): m/z calcd for C19H22N7O7S [M+H]+: 492.1301, Found 492.1311.

4.1.4  General method B for the synthesis of compounds 19,