The title compounds, dimethyl 5-amino-1-methoxy-2,3-pyridinedicarboxyl
ate, C10H12N2O5, and dimethyl 5-amino-1-methylthio-2,3-pyridinedicarbo
xy C10H12N2O4S, are not isomorphous but have similar packing and hydro
gen-bonding patterns. Both structures contain hydrogen-bonded ribbons,
with van der Waals contacts between the ribbons.