4-氧代四氢-2H-吡喃-3-羧酸甲酯 、 Bredereck 试剂 以to give crude title compound (101 mg) as a red oil which的产率得到methyl 5-[1-dimethylamino-methylidene]-4-oxo-tetrahydro-pyran-3-carboxylate
The invention relates to compounds of formula
wherein R1, R2, R3, R4, X and Y are as defined herein and to pharmaceutically active acid addition salts thereof. The compounds can be used for the treatment of Alzheimer's disease, cerebral amyloid angiopathy, hereditary cerebral hemorrhage with amyloidosis, Dutch-type (HCHWA-D), multi-infarct dementia, dementia pugilistica or Down syndrome.