Synlett 2003(1): 0118-0120
DOI: 10.1055/s-2003-36225
LETTER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Synthesis of New Enantiopure Building Blocks for the Preparation of Steroids

Lutz F. Tietze*, Tokala Ramachandar, Carsten Vock
Institut für Organische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany
Fax: +49(551)399476; e-Mail: ltietze@gwdg.de;
Further Information

Publication History

Received 9 August 2002
Publication Date:
18 December 2002 (online)

Abstract

The enantiopure α,β-unsaturated ketone 4 was synthesised from indanone 2 by a palladium-catalysed hydrogenolysis of allylic formate 10 followed by deprotection of TBS-ether 11 and oxidation with MnO2.

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Experimental Details for the Tsuji-Trost-Reaction: To a degassed solution of 10 (1.70 g, 4.31 mmol)in dioxane (15 mL) were added Pd(OAc)2 (10 mg, 0.045 mmol) and P(n-Bu)3 (0.040 mL, 0.18 mmol). The reaction mixture was stirred for 45 min at 90 °C. Then the reaction mixture was allowed to attain r.t. and diluted with Et2O and H2O. The organic layer was washed with brine, dried over Na2SO4, and concentrated in vacuo. Purification by silica gel column chromatography(pentane) afforded 1.06 g (70%) of 11 and 12 (4:1 mixture) as colourless oil, which was used for the next step without separation. Separation of 12 is possible using pentane/ethyl acetate (100:1), but easier at a later stage.

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Compound 3: Rf = 0.11 (pentane/ethyl acetate 10:1), [α]D 20 = +56.0 (c 1, CHCl3). 1H NMR (300 MHz, CDCl3): δ = 0.76 (s, 3 H), 1.14 (s, 9 H), 1.14-1.69 (m, 5 H), 1.86-2.05 (m, 1 H), 2.10-2.20 (m, 1 H), 2.32 (dd, J = 11.9, 7.0 Hz, 1 H), 3.54 (dd, J = 9.0, 6.8 Hz, 1 H), 4.41 (mc, 1 H), 5.60 (dt, J = 9.7, 2.6 Hz, 1 H), 5.73 (dt, J = 9.7, 1.5 Hz, 1 H). 13C NMR (50.3 MHz, CDCl3): δ = 10.93, 23.72, 27.98, 30.32, 43.08, 44.08, 44.76, 67.29, 71.65, 78.27, 128.80, 129.60.
Compound 4: Rf = 0.21 (pentane/ethyl acetate 10:1), [α]D 20 = +24.3 (c 1, CHCl3). 1H NMR (300 MHz, CDCl3): δ = 0.83 (d, J = 1.0 Hz, 3 H), 1.14 (s, 9 H), 1.53-1.69 (m, 2 H), 1.78-1.90 (m, 1 H), 2.01-2.14 (m, 1 H), 2.14 (dd, J = 16.2, 0.9 Hz, 1 H), 2.50-2.61 (m, 1 H), 2.60 (d, J = 16.2 Hz, 1 H), 3.71 (dd, J = 8.9, 7.0 Hz, 1 H), 5.96 (ddd, J = 9.9, 3.1, 0.8 Hz, 1 H), 6.81 (dd, J = 9.9, 2.3 Hz, 1 H). 13C NMR (50.3 MHz, CDCl3): δ = 11.95, 23.88, 28.54, 31.30, 44.32, 46.76, 52.08, 72.63, 78.70, 129.60, 149.80, 200.60.