1. The compound of the formula:! ! or a pharmaceutically acceptable salt thereof. ! 2. A composition comprising a compound according to claim 1 and a pharmaceutically acceptable diluent or carrier. ! 3. The composition according to claim 2, which is suitable for oral administration. ! 4. The composition according to claim 2 or 3 in solid form. ! 5. The composition according to claim 2 or 3 in liquid form. ! 6. The use of a compound according to claim 1 or a composition according to any one of claims 2-5 for the manufacture of a medicament for the treatment of a BH4-sensitive condition. ! 7. The use of claim 6, wherein the BH4-sensitive condition is selected from the group consisting of hypertension, peripheral arterial disease, intermittent claudication, critical limbal ischemia, heart failure, atherosclerosis, endothelial dysfunction, vascular disease, type II diabetes, diabetic retinopathy metabolic syndrome, endothelial dysfunction associated with type I diabetes, and diabetic nephropathy. ! 8. The use of claim 6, wherein the BH4-sensitive condition is a vascular disease. ! 9. The use of claim 8, in which the vascular disease is a disease selected from the group consisting of peripheral arterial disease, intermittent claudication, coronary artery disease, vascular disease associated with hypercholesterolemia, vascular disease associated with smoking, hypertension, resistant or uncontrolled hypertension, pulmonary arterial hypertension, idiopathic pulmonary hypertension, pulmonary hypertension in infants (PPHN), atherosclerosis, stroke, vasospasm after a stroke, myocardial infarction, ischemia-reperfusion t1. Соединение формулы: ! !или его фармацевтически приемлемая соль. ! 2. Композиция, содержащая соединение по п.1 и фармацевтически приемлемый разбавитель или носитель. ! 3. Композиция по п.2, которая подходит для перорального введения. ! 4. Композиция по п.2 или 3 в твердой форме. ! 5. Композиция по п.2 или 3 в жидкой форме. ! 6. Применение соединения п
