Enantioselective Syntheses of Heteroyohimbine Natural Products: A Unified Approach through Cooperative Catalysis

Abstract

Alstonine and serpentine are pentacyclic indoloquinolizidine alkaloids (referred to as "anhydronium bases") containing three contiguous stereocenters.E ach possesses interesting biological activity,w ith alstonine being the major component of ap lant-based remedy to treat psychosis and other nervous system disorders.T his work describes the enantioselective total syntheses of these natural products with ac ooperative hydrogen bonding/enamine-catalyzed Michael addition as the key step.

Protecting‐Group‐Free Total Synthesis and Biological Investigation of Cabucine Oxindole A†

“…The retrosynthetic analysis indicated that the dihydropyran functionality in cabucine oxindole A (1, Scheme 1) could be obtained from the lactone motif in pentacyclic compound 2 via a late-stage Korte rearrangement. [7] A facile oxidative rearrangement, chemoselective reduction and lactone formation should convert β-tetrahydrocarboline 3 into spirooxindole pentacycle 2 bearing the unique spiro[pyrrolidine-3,3'-oxindole] motif. Lastly, we envisaged that the quinolizidine skeleton in 3 can be achieved from 5-methoxytryptamine (4) via a one-pot, organocatalytic asymmetric reaction cascade.…”

Sarpagan bridge enzyme has substrate-controlled cyclization and aromatization modes

“…Serpentine ( 7 ) was obtained from ChemFaces Biochemical Co.,Ltd. Alstonine was produced by oxidation of tetrahydroalstonine ( 4 ) with Pd black following a procedure by Younai et al23 (NMR spectrum see Supplementary Fig. 3).…”

Relay Catalysis of Bismuth Trichloride and Byproduct Hydrogen Bromide Enables the Synthesis of Carbazole and Benzo[α]carbazoles from Indoles and α‐Bromoacetaldehyde Acetals

“…2‐(1 H ‐Indol‐3‐yl)acetaldehyde (4 b) : 0.6 g, 78%; brown liquid; 1 H (400 Hz, CDCl 3 , 25 °C, TMS): δ =3.80 (d, J =1.2 Hz, 2H), 7.13–7.17 (m, 2H), 7.20–7.25 9 m, 1H), 7.38 (d, J =8.0 Hz, 1H), 7.54 (d, J =8.0 Hz, 1H), 8.22 (s, 1H), 9.76 ppm (t, J =2.4 Hz, 1H); 13 C NMR (100 Hz, CDCl 3 , 25 °C, TMS): δ =40.5, 106.2, 111.5, 118.6, 120.1, 122.7, 123.6, 127.5, 136.4, 199.8 ppm.…”