C([O:8][CH2:9][CH2:10][CH:11]1[CH2:16][CH2:15][C:14]([CH3:18])(O)[CH:13]([CH2:19][CH3:20])[CH2:12]1)C1C=CC=CC=1.C(Cl)(=O)C(Cl)=O.CS(C)=O.CCN(CC)CC>C(Cl)Cl>[CH2:19]([C:13]1[CH2:12][CH:11]([CH2:10][CH:9]=[O:8])[CH2:16][CH2:15][C:14]=1[CH3:18])[CH3:20]The deprotected alcohol was oxidized by the standard “Swern” procedure (Mancuso, Synthesis 1981 p 165, incorporated herein by reference) as follows: The alcohol (5 mmol) was added to a solution of oxalyl chloride (3.5 mL, 7.0 mmol) in CH2Cl2 (30 mL) with DMSO (0.64 mL, 9.0 mmol) at −78 EC. After 40 min., NEt3 (2.50 mL) was added and the mixture was warmed to rt. After standard aqueous work-up and purification, (3-ethyl-4-methyl-cyclohex-3-enyl)-acetaldehyde (Intermediate K5) was isolated (˜90%).
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