This is a report of the detection of 13-ethoxy-8α α α α α,13-epoxy-14,15,16-trinorlabdane (1) and 12-ethoxy-8α α α α α,12-epoxy-13,14,15,16-tetranorlabdane (2), hitherto unidentified and considered as degradation products of ambrein, among 31 constituents found by analysis of ambergris tincture. Copyright © 2004 John Wiley & Sons, Ltd.KEY WORDS: ambergris; tincture; 13-ethoxy-8α,13-epoxy-14,15,16-trinorlabdane; 12-ethoxy-8α,12-epoxy-13,14,15,16tetranorlabdane * Correspondence to: K. Awano, Technical Research Centre, T. Hasegawa Co. Ltd, 335-Kariyado, Nakahara-ku, Kawasaki-shi 211, Japan. E-mail: Ken-ichi_Awano@t-hasegawa.co.jp Distillation of tinctureAfter removing ethanol from the extract under atmospheric pressure to concentrate it to 200 ml, the ethanol was again distilled off carefully under 30 mmHg, to give 81 g extract. Since the residual tincture contained a considerable amount of compounds with high boiling points, it was distilled at 120°C/0.1 mmHg, to give 0.65 g (yield of 0.65% from the starting ambergris) of distillate. The distillate, exhibiting a strong aroma, was separated into several fractions by silica gel column chromatography, which were then analysed by GC, GC-MS and GC-IR. GC ConditionsAnalyses were done using a Hewlett-Packard 5890II gas chromatograph with a 0.25 mm i.d. × 60 m capillary column coated with PEG-20M. Column temperature, 70°C to 220°C at a rate of 3°C/min; carrier gas, nitrogen at a flow rate of 1 ml/min; injector and detector temperature, 250°C. GC-MS, GC-IR ConditionsA Hewlett-Packard 5970 mass spectrometer and HewlettPackard 5965B infrared spectrometer were used. The column conditions were the same as those described for GC. Carrier gas, helium at a flow rate of 1 ml/min; ionization voltage, 70 eV. NMR ConditionsThe NMR spectra were recorded on a JEOL LA400 spectrometer, using tetramethylsilane as an internal standard.

Synthesis of α-ambrinol was successfully accomplished by cyclization of dihydro-γ-ionone ethylene acetal which was prepared by the titanium(IV)-promoted reaction of 3,3-dimethyl-1-trimethylsiloxycyclohexene with methyl vinyl ketone ethylene acetal followed by exo-methylenation with triphenylphosphonium methylide.

Enamines, prepared readily from various carbonyl compounds, react with acetals or trialkyl orthoformates in the presence of Lewis acids such as BF3·OEt2 to give corresponding β-alkoxy carbonyl compounds or α-dialkoxymethyl carbonyl compounds in good yields. The reaction of dienamines with acetals or trialkyl orthoformates also selectively gives corresponding β,γ-unsaturated α-(α-alkoxyalkyl) carbonyl compounds or β,γ-unsaturated α-diakoxymethyl carbonyl compounds in good yields.

Enamines react with aldehydes in the presence of Lewis acids such as BF3·OEt2 to give the corresponding crossed aldol products in good yields. Reaction of dienamines with aldehydes gives the corresponding β,γ-unsaturated α-(1-hydroxyalkyl) carbonyl compounds.

The Lewis acid-catalysed reaction of 1-trimethylsiloxy-1,3-cyclohexadienes with aldehydes and trialkyl orthoformates afforded the corresponding 4-substituted 2-cyclohexenones. A new reaction of 2,4,6-trienones with m-chloroperbenzoic acid followed by the reduction with zinc in acetic acid gave 7-hydroxy-3,5-dienones. Utilizing these efficient reactions, megastigma-4,6,8-trien-3-ones, 3-hydroxy-β-ionol, 3-hydroxy-β-ionone, 5,6-epoxy-3-hydroxy-β-ionol, and 3-oxo-α-ionol were successfully synthesized.