Compound 26
(3R,5S)-di-tert-butyl 5-formyl-3-methylcycloheptane-1,1-dicarboxylate
From: Direct, enantioselective α-alkylation of aldehydes using simple olefins
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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
Prepared according to the general procedure outlined for compound 13 using di-tert-butyl 2-(2-methylallyl)-2-(4-oxobutyl)malonate with 10 equiv. H2O, at 10 °C. Purified by flash chromatography (10-20% EtOAc/hexanes) to provide the title compound (72 mg, 71% yield, 9:1 dr, 84% ee) as a colorless oil. Analytical data: [α]D21+12.6 (c = 1.00, CHCl3); 1H NMR (500 MHz, CDCl3): δ 9.61 (s, 1H), 9.58 (s, 1H), 2.47-2.42 (m, 1H), 2.35-2.28 (m, 1H), 2.26-2.20 (m, 2H), 2.14 (dd, J = 14.5 Hz, 6.5 Hz 2H), 2.04-1.91 (m, 6H), 2.04-1.91 (m, 6H), 1.88-1.70 (m, 4H), 1.61-1.53 (m, 4H), 1.44 (s, 9H), 1.43 (s, 9H), 1.04 (d, J = 6.8 Hz, 3H), 1.01 (d, J = 6.8 Hz, 3H); 13C NMR (125 MHz, CDCl3): δ 204.4, 203.7, 171.9, 171.7, 170.8, 81.3, 81.2, 81.0, 80.9, 58.2, 57.6, 53.1, 49.8, 41.6, 40.9, 37.7, 35.1, 32.2, 30.9, 29.4, 27.9, 27.8, 27.1, 24.9, 24.5, 22.9, 22.2; HRMS (ESI+) Calcd. for C19H32O5+H, 363.2142; Found, 363.2142; IR (thin film, cm-1) 2975, 2932, 1720, 1456, 1367, 1250, 1138, 1058, 848, 735, 704; TLC (60:40 hexanes:EtOAc): Rf= 0.68. SFC analysis of the corresponding 2-napthoyl ester (AD, 4% EtOH/CO2, 3.0 mL/min, 100 bar) indicates 84% ee: tR= 7.5, 9.4 min.
