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Synlett 2003(13): 1977-1980  
DOI: 10.1055/s-2003-42077
LETTER
© Georg Thieme Verlag Stuttgart · New York

Asymmetric Total Synthesis of Pseudoplexaurol and 14-Deoxycrassin, two Antitumor Marine Cembrane Diterpenoids

Zuosheng Liu, Lizeng Peng, Weidong Z. Li, Yulin Li*
National Laboratory of Applied Organic Chemistry and Institute of Organic Chemistry Lanzhou University, Lanzhou, Gansu 730000, P. R. China
Fax: +86(931)8912283; e-Mail: lilyl@lzu.edu.cn;
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Publication History

Received 12 June 2003
Publication Date:
08 October 2003 (online)

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Abstract

The first asymmetric total synthesis of two naturally occurring­ antitumor pseudoplexaurol and 14-deoxycrassin were achieved via two convergent synthetic sequences featured a chiral pool protocol to implement C-1 stereogenic center and Ti(0)-mediat­ed cyclization leading to cembrane ring.

Key words

14-deoxycrassin - diterpenoids - cembranoids - total synthesi­s

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Data of pseudoplexaurol (2): [α]D 20 -19.5 (c 0.40, CHCl3).
IR (film): νmax = 3413 (brs), 2924, 2855, 1647, 1449, 1381, 1031, 898 cm-1. LRMS (EI): m/z (%) = 304 (M, 0.9), 286 (2.8), 273 (7.2), 255 (4.9), 215 (7.2), 201 (8.3), 189 (12), 173 (15), 161 (27), 147 (39), 133 (78), 119 (70), 107 (77), 93 (90), 81 (100), 79 (77), 67 (87), 55 (67), 43 (55), 41 (59). 1H NMR (400 MHz, CDCl3): δ = 5.14 (1 H, d, J = 1.0 Hz, CH=), 5.06 (1 H, t, J = 6.4 Hz, CH=), 5.05 (1 H, dd, J = 6.4 Hz, CH=), 4.96 (1 H, d, J = 1.4 Hz, CH=), 4.11 (2 H, s, CH2O), 2.65 (1 H, dd, J = 3.7, 7.0 Hz, epoxy H), 2.25-2.00 (11 H, m, 5 CH2, CH), 1.72-1.52 (4 H, m, 2 CH2), 1.63 (3 H, s, CH3), 1.59 (3 H, s, CH3), 1.22 (3 H, s, CH3). HRMS (ESI) calcd for C20H32O2Na: 327.2295. Found for [M + Na]+: 327.2295.

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Data of 14-deoxycrassin (1): [α]D 20 +21 (c 0.06, CHCl3).
IR (film): νmax = 3393 (brs), 2928, 2851, 1726, 1642, 1437, 1382, 1105, 1065, 906 cm-1. LRMS (EI): m/z (%) = 318 (M, 14), 300 (M - 18, 43), 285 (25), 272 (14), 257 (18), 247 (9), 243 (14), 229 (22), 215 (21), 193 (82), 175 (52), 161 (41), 147 (66), 133 (55), 121 (69), 107 (73), 93 (73), 81 (100), 79 (68), 67 (22), 55 (48), 53 (46), 43 (44). 1H NMR (400 MHz, CDCl3): δ = 6.58 (1 H, s, CH=), 5.76 (1 H, s, 1 H), 5.19 (1 H, t, J = 6.5 Hz, CH=), 5.07 (1 H, t, J = 6.4 Hz, CH=), 4.48 (1 H, d, J = 11.5 Hz, CHO), 2.74-2.67 (1 H, m, CH), 2.55-2.48 (2 H, m, CH2), 2.16-2.06 (6 H, m, 3 CH2), 1.95-1.81 (4 H, m, 2 CH2), 1.76 (3 H, s, CH3), 1.72 (3 H, s, CH3), 1.46-1.40 (2 H, m, CH2), 1.25 (3 H, s, CH3). HRMS (ESI) calcd for C21H32O3Na: 341.2087. Found for [M + Na]+: 341.2082.