Synlett 2006(11): 1691-1694  
DOI: 10.1055/s-2006-944225
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthetic Studies towards (-)-Lemonomycin, Synthesis of Fused Tetracycles

Cédric Couturiera, Thierry Schlamab, Jieping Zhu*a
a Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette Cedex, France
b Société Rhodia, Centre de Recherches de Lyon, 69192 Saint-Fons Cedex, France
Fax: +33(1)69077247; e-Mail: zhu@icsn.cnrs-gif.fr;
Further Information

Publication History

Received 21 March 2006
Publication Date:
04 July 2006 (online)

Abstract

The asymmetric synthesis of 1,3-lactol-bridged tetrahydroisoquinoline 5 is developed. Subsequent cyclization of 5 under acidic conditions leads to the formation of a tricyclic enamide 22, which is in turn converted to a tetracyclic compound 23.

18

For successful cyclization using enolate chemisty in related system, see ref. 6 and 17a.

20

Compound 23: [α]D 25 +37.1 (c 0.04, CHCl3). IR (CHCl3): 3623, 3025, 3017, 2975, 2928, 1727, 1455, 1391, 1260, 1201, 1046 cm-1. 1H NMR (600 MHz, CDCl3): δ = 8.01 (d, J = 2.2 Hz, 1 H), 5.87 (s, 1 H), 4.75 (dd, 1 H, J = 2.2, 8.5 Hz), 4.46 (d, 1 H, J = 2.0 Hz), 3.95 (br d, 1 H, J = 11.5 Hz), 3.70 (s, 3 H), 3.68 (m, 1 H), 3.65 (m, 1 H), 3.64 (s, 3 H), 3.45 (m, 1 H), 3.11 (dd, 1 H, J = 1.7, 12.1 Hz), 2.41 (br d, 1 H, J = 12.1 Hz), 2.14 (s, 3 H), 1.87 (dt, 1 H, J = 3.7, 13.1 Hz), 1.82 (m, 1 H), 1.41 (br d, 1 H, J = 13.9 Hz) ppm. 13C NMR (300 MHz, CDCl3): δ = 159.0, 145.4, 141.0, 130.7, 123.4, 121.8, 100.3, 83.8, 67.3, 62.6, 61.6, 61.1, 57.4, 30.4, 20.5, 9.6 ppm. HRMS (ESI): m/z cacld for C19H24N2O5 + H+: 361.1763; found: 361.1756.