Ethyl(1R,2S,3S,4S)-2-(furan-2-yl)-3-nitro-6-oxobicyclo[2.2.2]octane-1-carboxylate

Ethyl(1R,2S,3S,4S)-2-(furan-2-yl)-3-nitro-6-oxobicyclo[2.2.2]octane-1-carboxylate

Compound 7 Ethyl(1R,2S,3S,4S)-2-(furan-2-yl)-3-nitro-6-oxobicyclo[2.2.2]octane-1-carboxylate To a solution of CAT 10 (128 mg, 0.37 mmol) and the nitroolefin 9 (3.1 g, 22.3 mmol) in 10 mL anhydrous CH2Cl2 at room temperature was added enone 8 (1.8 g, 10.7 mmol). The resulting mixture was stirred at the same temperature until enone 8 is consumed as indicated by TLC. Then DBU (0.34 mL, 3.20 mmol) was added and the mixture was allowed to stir at ambient temperature until completion as indicated by TLC. The solution was concentrated in vacuo and purified by flash chromatography on silica gel (Hexane / EtOAc = 20 / 1) to give 7 (2 g, 61% yield) as a yellow solid. [α]D 23 28.0 (c = 1.0, CHCl3).

1H NMR (400 MHz, CDCl3): δ 7.29 (d, J = 0.8 Hz, 1H), 6.27 (dd, J = 2.0 Hz, J = 3.2 Hz, 1H), 6.14 (d, J = 4.0 Hz, 1H), 4.93 (m, 1H), 4.57 (d, J = 4.4 Hz, 1H), 4.11 (m, 2H), 3.04-3.02 (m, 1H), 2.80-2.75 (m, 1H), 2.60- 2.54 (m, 1H), 2.33-2.29 (m, 1H), 1.88-1.72 (m, 2H), 1.33-1.23 (m, 1H), 1.21 (t, J = 7.2 Hz, 3H).

13C NMR (100 MHz, CDCl3): δ 204.1, 168.7, 151.8, 142.5, 110.5, 108.1, 88.3, 61.3, 56.3, 42.0, 40.8, 33.7, 26.9, 19.2, 13.8.

IR (thin film): 3435, 3141, 3120, 2996, 2959, 1715, 1653, 1621, 1557, 1505, 1473, 1443, 1408, 1371, 1336, 1301, 1336, 1301, 1270, 1236, 1142, 1120, 1083, 1062, 1074, 1045, 1045, 1011, 996, 960, 930, 892, 884, 867, 803, 753, 628, 600, 508, 436 cm-1 .

LRMS (ESI): 308.0 (M+H)+ , 330.0 (M+Na)+ .

HRMS (ESI): calcd for C15H18O6N (M+H) + : 308.1129. Found: 308.1130.

Melting point: 117-118 oC.

Concise asymmetric total synthesis of (−)-patchouli alcohol

Guang-Qiang Xu,a  Guo-Qiang Lina  and  Bing-Feng Sun*a 

 Author affiliations

*Corresponding authors

aCAS Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, 345 Lingling Road, Shanghai 200032, China
E-mail: bfsun@sioc.ac.cn

Abstract

The asymmetric total synthesis of (−)-patchouli alcohol was accomplished in a concise manner. Key reactions include a highly diastereo- and enantioselective formal organocatalytic [4 + 2] cycloaddition reaction, a radical denitration reaction, and an oxidative carboxylation reaction. The formal synthesis of norpatchoulenol was achieved as well.

• This article is part of the themed collection: Synthetic Approaches to Natural Products via Catalytic Processes

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