Inhibition of Human Leucocyte Elastase by Novel Thieno-1,3-oxazin-4-ones and Thieno-1,3-thioxazin-4-ones

In this paper we report the synthesis and the inhibition on Human Leucocyte Elastase (HLE) of a new series of thieno[2,3-d][1,3]oxazin- or thioxazin-4-ones 3a-o and thieno[3,2-d][1,3]oxazin- or thioxazin-4-ones 6a-d. New derivatives have inhibitory activity in the micromolar range and among them, 2-(3-trifluoromethylphenylamino)-4H-thieno[2,3-d][1,3]oxazin-4-one 3h and 5,6-dimethyl-2-(4-nitrophenylamino)-4H-thieno[2,3-d][1,3]thioxazin-4-one 3o were the most interesting.