Fig. 4: Total synthesis of secu’amamine D (6) and securingine A (7b) via divergent 1,2-Meisenheimer rearrangement and Cope elimination. | Nature Communications

Fig. 4: Total synthesis of secu’amamine D (6) and securingine A (7b) via divergent 1,2-Meisenheimer rearrangement and Cope elimination.

From: Collective total synthesis of C4-oxygenated securinine-type alkaloids via stereocontrolled diversifications on the piperidine core

Fig. 4: Total synthesis of secu’amamine D (6) and securingine A (7b) via divergent 1,2-Meisenheimer rearrangement and Cope elimination.The alternative text for this image may have been generated using AI.

Reagents and conditions: (a) B2pin2 (1.1 equiv), CuCl (0.02 equiv), NaOtBu (0.03 equiv), 25 (0.04 equiv), MeOH (2.0 equiv), THF, 23 °C; (b) NaBO3·H2O (5.0 equiv), THF:H2O (1:1 v/v), 23 °C, 54% (2 steps); (c) Me3OBF4 (3.0 equiv), proton-sponge (4.0 equiv), CH2Cl2, 0 °C to 23 °C, 72% (96% ee); (d) LiEt3BH (1.2 equiv), THF, –78 °C; (e) TIPSOTf (1.2 equiv), Et3N (2.0 equiv), Et2O, 0 °C to 23 °C; 28 (1.5 equiv), Bu2BOTf (1.2 equiv), Et2O, –78 °C; (f) TBAF (2.2 equiv), THF, 23 °C, 61% (2 steps); (g) TFA:CH2Cl2 (1:1 v/v), 23 °C; (h) Et3N:MeOH (1:2 v/v), 50 °C, 90% (2 steps); (i) m-CPBA (1.1 equiv), K2CO3 (3.0 equiv), CH2Cl2, 0 °C to 23 °C, 83%; (j) MsCl (3.0 equiv), Et3N (6.0 equiv), CH2Cl2, 0 °C, 87%; (k) m-CPBA (1.1 equiv), K2CO3 (3.0 equiv), CH2Cl2, 0 °C to 23 °C, 75%. B2pin2 bis(pinacolato)diboron, TBAF tetra-n-butylammonium fluoride, TFA trifluoroacetic acid, m-CPBA 3-chloroperbenzoic acid.

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