FIELD: medicine； pharmaceuticals.SUBSTANCE: present invention relates to a novel compound of formula I, or a pharmaceutically acceptable salt or stereoisomer thereof, having properties of a PI3K-alpha inhibitor and relative selectivity for PI3K-delta. In formula I I R1 is selected from hydrogen, C1-5alkyl or C3-8cycloalkyl, where R1 is optionally substituted with 0, 1 or 2 groups independently selected from hydrogen, fluorine and chlorine； R2 is selected from cyclopropyl, isobutyl, 2-methylpropyl, methyl, ethyl, iodine, pyridazinyl, pyrimidinyl, pyrazinyl, pyridinyl, pyrrolidinyl, piperidinyl, ethoxycarbonyl, cyclohexyl, phenyl, quinazolinyl, isoquinolinyl, pyrazolyl, imidazolyl, indolyl, indazolyl, thiazolyl, pyrazolo[1,5-a]pyrimidinyl, 3,6-dihydro-2H-pyranyl, 1H-pyrrolo[2,3-b]pyridinyl, cyclobutyl, 1H-pyrazolo[3,4-b]pyridinyl, pyrrolo[2,3-b]pyridinyl, benzimidazolyl, morpholinyl, 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridinyl, 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazolyl, where R2 is substituted with 0, 1 or 2 independently selected R3； n is 0, 1, 2, or 3； A is C3-12cycloalkyl, mono- or bicyclic C3-7heterocycloalkyl, containing a nitrogen atom as a heteroatom, and C6-12spirocyclyl containing a nitrogen atom in the ring； L is selected from O, S, SO2 and -CH2； K is selected from a bond, O, N((C1-5)alkyl)1-2 and -C(O)N(Rb)-(CH2)m； Rb is H or C1-10alkyl； m has the value 0； R3 is independently selected from a fluorine atom, chlorine atom, methyl, ethyl, propyl, methoxy, pyrazolyl, thiazolyl, benzisoxazolyl, pyrazinyl, cyclopropyl, pyridinyl, cyclopropylmethyl, hydroxy, oxo, dimethylamino, morpholinyl, imidazolyl, pyrrolidinyl, piperidinyl, tert-butyl, trifluoromethyl, methoxymethyl, isoxybutylcarboxy, tert-butylcarboxy, phenylcarboxy, hydrogen, methylpropylcarboxy, ethoxycarbonyl and others indicated in the claims, where each R3 is substituted with 0, 1, 2 or 3 substituents R4 and each R4 is independently selected from methyl, trifluoromethyl, methoxy, amino, dimethylamino, flu
