Total synthesis of the Amaryllidaceae alkaloid clivonine

Abstract

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Total Synthesis of (±)‐8‐Oxo‐erythrinine, (±)‐8‐Oxo‐erythraline, and (±)‐Clivonine

“…Various reaction conditions were tested (including using CAN [cerium(IV) ammonium nitrate],28 BrCN,29 and Ac 2 O/NaOAc30), but these led either to the recovery of the starting material or to the formation of a mixture of unidentified products. However, amine 6 was converted into the ring‐opened product in a relatively low yield (30 %; 70 % based on recovered starting material) when it was exposed to PhOCOCl/CH 2 Cl 2 31,32 at room temperature. The resulting NMR spectroscopic data were consistent with those reported in the literature.…”

Asymmetric Total Syntheses of (−)‐α‐Lycorane, (−)‐Zephyranthine, and Formal Synthesis of (+)‐Clivonine

“…Previously, intermediate 1 was either synthesized in racemic form or derived from the optically pure natural product, (−)‐lycorine ( 6 ) . Lycorenine‐type Amaryllidaceae alkaloid (+)‐clivonine ( 5 ) could be synthesized via a lycorine‐type precursor 4 by a “ring‐switching” strategy, according to a procedure reported by Oppolzer and co‐workers . We surmised that the lycorine‐type precursor 4 could also be accessed through the common intermediate 1 .…”

“…In contrast, if dihydroxylation of 1 was performed using AD‐mix‐α (5:2 d.r., see the Supporting Information) followed by protection of the diol with 2,2‐dimethoxypropane 32 , acetonides 33 a (51 % yield) and 33 b (22 % yield) were obtained, respectively. The latter ( 33 b ) corresponded to the lycorine‐type intermediate 4 in the total synthesis of the lycorenine‐type natural product (+)‐clivonine ( 5 ) through a “ring‐switching” process (Scheme ) . The absolute configuration of 33 a could be determined through X‐ray crystal analysis (Figure ).…”

Amaryllidaceae and Sceletium alkaloids

“…99 Two different strategies have been developed for the synthesis of alkaloid clivonine 201 from the intermediate 7arylhydrindane 202. 100 The rst asymmetric total synthesis of natural (+)-clivonine was thus achieved by using the optically pure 202 derived from the enantiomerically pure enone (+)-203. The dibenzoazocane motifs 212, related to the apogalanthamine-type Amaryllidaceae alkaloids, have been synthesized from the catechol intermediate 213 using enzymatic oxidative cyclisation reactions.…”