An optically active (-)-7-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-5-[(3S)-3-piperidinyl]-1,4- -dihydro-2H-pyrido[2,3-d][1,3]oxazin-2-one of the formula (I) or salt thereof. The compound has an excellent anti-inflammatory activity, and other biological activity ##STR00001##