Lycorine structure-activity relationships

Twenty three lycorine derivatives and naturally occurring alkaloids, structurally related to lycorine, were tested for their ability to inhibit ascorbic acid biosynthesis in potato tubers. The following relationships between structure modification and activity were observed: (a) cleavage of the acetalic bonds on the dioxole ring had no effect on activity; (b) derivatives with a methoxy group on C-8 (A ring) were inactive; (c) oxidation of NCH2-7 to an amide group (B ring) caused loss of activity; (d) modification of the C/D ring junction had no effect on activity when the D ring assumed a β configuration whereas a great decrease of activity was observed when that ring assumed an α configuration; (e) selective or complete acetylation of hydroxyl groups of the C ring, epimerization or oxidation of the hydroxyl group on C-2 led to a loss of activity; (f) a compound with a double bond located in the 1,2 position showed activity almost identical to lycorine; (g) stereoselective hydrogenation of the double bond of the C ring induced a considerable increase of the activity; (h) protonation of the nitrogen atom had no effect on activity.