Acetylenchemie. 4 mitt. Synthese von haplophyllin und N-methylflindersin,zwei wege zu N-funktio-nalisierten pyrano[3,2-c]chinolin-alkaloiden

Pyrano3,2-c]quinoline alkaloids 3 , suitable precursor for photobiomimetic dimerisations, are available by ptc-reactions of 4-hydroxyquinoline-2-ones 1 with 3-chloro-3-methylbut-1-yne, as byproducts uro3,2-c]-quinoline-2-one is isomeres 5 are found. In the synthesis of flindersine ( 3a ) additionally the oxazolo3,2-a]quinolin-5-one 4 could be isolated, while in the preparation of N-methylflindersine ( 3b ) a bis-(N-methyal-4′-hydroxyquinolin-2′-one-3′-yl)isopentene ( 7 ) was identified. Alkaloid dimers, which may be formed from the intermediates 6 , were not present. The structure of 7 confirms reaction pathways, discussed previously. Haplophylline ( 3c ) is synthesized for the first time by N-alkylation a of 3a with 3-methylcrotonyal chlormethyl ester.