Total Synthesis of (±)-Ceratopicanol: Application of Pd-Catalyzed Enediyne Cycloreduction

Abstract

Pd-catalyzed cycloreduction of enediyne 3 successfully afforded the linear triquinane skeleton 4. Total synthesis of (±)-ceratopicanol was accomplished using additional eight-step transformations starting from 4.

ceratopicanol - palladium - enediyne - cycloreduction - triquinane

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All new compounds were fully characterized by ¹H NMR, ¹³C NMR, IR, HRMS (or elemental analysis).
Ceratopicanol ( 11): ¹H NMR (400 MHz, CDCl₃): δ = 3.71 (dd, J = 10.0, 7.2 Hz, 1 H), 2.49 (m, 1 H), 2.34 (ddd, J = 11.3, 8.3, 8.3 Hz, 1 H), 2.15 (dd, J = 14.0, 9.6 Hz, 1 H), 1.88 (m, 1 H), 1.67 (ddd, J = 13.0, 8.4, 1.2 Hz, 1 H), 1.56 (m, 1 H), 1.50-1.32 (m, 5 H), 1.23 (dd, J = 13.0, 4.8 Hz, 1 H), 1.08 (dd, J = 13.8, 6.8 Hz, 1 H), 1.04 (s, 6 H), 0.88 (s, 3 H), 0.87 (s, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 82.62, 58.80, 54.96, 51.23, 48.77, 44.18, 41.94, 41.68, 40.85, 39.56, 31.54, 30.60, 28.54, 23.66, 21.25. FT-IR (neat): 3310 (-OH, br s) cm^-1.
Isomer of Ceratopicanol (11β): ¹H NMR (400 MHz, CDCl₃): δ = 3.88 (m, 1 H), 2.64 (h, J = 8.0 Hz, 1 H), 2.45 (dt, J = 11.2, 9.6 Hz, 1 H), 2.08 (dtd, J = 13.6, 9.2, 5.6 Hz, 1 H), 1.79 (ddd, J = 11.6, 11.4, 5.6 Hz, 1 H), 1.65-1.54 (m, 2 H), 1.46 (s, 1 H), 1.44 (s, 1 H), 1.38 (ddd, J = 12.8, 8.8, 2.0 Hz, 1 H), 1.31 (d, J = 4.0 Hz, 1 H), 1.28 (m, 1 H), 1.11-1.06 (m, 2 H), 1.04 (s, 3 H), 0.95 (s, 3 H), 0.91 (s, 3 H), 0.79 (s, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 81.16, 59.62, 54.63, 52.27, 49.83, 44.25, 41.44, 40.97, 39.85, 32.81, 30.25, 29.35, 28.15, 23.69, 19.63. FT-IR (neat): 3320 (-OH, br s) cm^-1. HRMS (ES): m/z calcd for C₁₅H₂₆ONa⁺: 245.1881; found: 245.1872.