The methylester of 3,4-dihydroxy-pyridine-6-carboxylic acid (1) reacts with bromochloromethane/potassjumcarbonate leading to the methylester of pyrido[3,4-d][1,3]-dioxole-6-onrhoxylic apid (2a). 2,3-Dihydroxy-pyridine (3a), 6-methyl- (3b), 5-chloro- (3c), and 5-bromo-2,3-dihydroxy-pyridine (3d) lead under the same conditions to the pyrido-[2,3-d][1,3]dioxole derivatives 4a, 4b, 4c, and 4d. The ester of 2,3-dihydroxy-pyridine-5-carboxylic acid (3e) and 4,6-dibromo-2,3-dihydroxy-pyridine (3f) also can be subjected to methylenation yielding the pyrido[2,3-d][1,3]dioxole compounds 4e and 4f. Treatment of 6-bromo-pyrido[2,3-d][1,3]dioxole (4d) with n-butyllithium gives 6- lithium-pyrido[2,3-d][1,3]dioxole (5a) allowing reaction with carbondioxide, N,N-di- methylformamide, N,N-dimethylacetamide, and sulphur/iodine to obtain the carboxylic acid 5b, the aldehyde of, the ketone 5g, and the disulfide 5n. The structures of compound 5b, 5f, and 5g were proofed by synthesis of derivatives.