- Model Studies of Terpene Biosynthesis. Intermolecular 1'-2 Electrophilic Condensation of 3-Methyl-2-butenyl Acetate
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The stereochemistry of the carbon-carbon bond-forming step in the electrophilic intermolecular 1'-2 condensation of 3-methyl-2-butenyl acetate (1-OAc) to yield lavandulyl acetate (2-OAc) was studied.Treatment of (1S)-3-methyl-2-butenyl acetate ((1S)-1-OAc) with aluminum trichloride in ethyl acetate gave labeled lavandulyl acetate (2-OAc) (30percent) and isoprene (65percent) as the major products.The configurations at C(1), C(2), and C(3) and the relative abundances of the diastereomers of 1-OAc were determined by converting the mixture to 3-(2'-propyl)-butyrolactone (3).The intensities of 1H resonances characteristic of each diastereomer were measured with the aid of Pirkle's chiral shift reagent, (S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol.The analysis showed that equal amounts of the (1S,2S,3R), (1S,2R,3R), (1S,2S,3S), and (1S,2R,3S) diastereomers of 2-OAc were obtained, signifying that the 1'-2 condensation was stereorandom at C(1) of the electrophilic isoprene unit.
- King, Chi-Hsin R.,Poulter, C. Dale
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p. 1413 - 1420
(2007/10/02)
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