Sedum acre (Cressulaceae) contains a variety of 2- and 2,6-substituted piperidine alkaloids. We now wish to report the isolation from this species of a new minor base, sederine C₁₇H₂₅NO₃ (by ms, M⁺ at 291 u.; hydrochloride: m.p. 199-201°C (uncorr.), [α]ᵈ²⁰ -82° (methanol, c = 1.4) which was assigned structure 1 on the basis of chemical and spectroscopic evidence. This structure represents the first example of a naturally occurring Sedum alkaloid with an ester function. The ¹H nmr spectrum of sederine (CDCl₃, TMS = 0) showed the presence of a N-CH₃ group, a methyl ester function, a C₆H₅-CHOH-CH₂ side chain, two protons on carbon atoms adjacent to the nitrogen, a methylene group α to the ester carbonyl, and remaining protons between 0.9 and 2.1 ppm. Acetylation of sederine led to 0-acetylsederine (M⁺ at 333 u.). Jones oxidation yielded the corresponding ketone (M⁺ at 289 u.), confirming the secondary hydroxyl group. LiAlH₄ reduction afforded a diol C₁₆H₂₅NO₂ (M⁺ at 263 u.; diacetyl derivative: M⁺ at 347 u.), ascertaining the methyl ester. The fragmentation pattern of sederine and its derivatives is characteristic of a 2,6-disubstituted N-methylpiperidine; major fragment ions in sederine's mass spectrum were at m/z 218, 170, and 96. Work is in progress to establish the stereochemistry of sederine.