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REPRINTS
Synthesis of Norchrysanthemic Acid Methyl Ester
1007
(1R,3R)-2,2-Dimethyl-3-((1E)-
propenyl)cyclopropanecarboxylic Acid Methyl Ester (1b)
To a stirring mixture of chromium(II) chloride (0.85 g, 6.9 mmol) in
tetrahydrofuran (20 ml) was added a mixture of (1R)-trans-caronaldehydic
acid methyl ester (0.16 g, 1.0 mmol) and 1,1-diiodomethane (0.60 g,
2.1 mmol) in tetrahydrofuran (5 mL). The mixture was stirred for 15 hr. It
was filtered on a Celite pad, the filtrate was poured onto water and then
extracted with t-butyl methyl ether, washed with brine, dried over sodium
sulfate and concentrated under reduced pressure. The residue was chromato-
graphed on silica gel with t-butyl methyl ether þ hexane (1 þ 100 by volume)
as eluant to give a 93 : 7 mixture of the methyl esters 1b and 1a (0.11 g, 63%)
as a colorless oil. [a]D24 þ 318 (c ¼ 2.4, CHCl3). NMR dH (CDCl3): 1.14
(3H, s), 1.24 (3H, s), 1.48 (1H, d, J ¼ 5.3), 1.68 (3H, dd, J ¼ 6.5, 1.6), 2.00
(1H, dd, J ¼ 5.3, 8.2), 3.66 (3H, s), 5.24 (1H, ddq, J ¼ 15.2, 8.2, 3.1), 5.61
(1H, dq, J ¼ 15.2, 6.5). IR nmax (neat): 2990, 1740, 1450, 1220, 1180 cm21
EIMS m/z: 168 (Mþ, 14), 153 (10), 109 (100).
.
(1R,3S)-2,2-Dimethyl-3-((1Z)-
propenyl)cyclopropanecarboxylic Acid Methyl Ester (1c)
A solution of potassium tert-butoxide (42 g, 380 mmol) in tetrahydrofuran
(500 mL) was dropped to a stirring mixture of (ethyl)triphenylphosphonium
bromide (150 g, 400 mmol) and tetrahydrofuran (500 mL) over 30 min under
nitrogen atmosphere at 2408C for 15 min. (1R)-cis-Caronaldehydic acid
hemiacetal (25.0 g, 176 mmol) was dropped to the mixture over 30 min at the
same temperature and was left to stand at room temperature for 2 hr. The
reaction mixture was poured onto 10% aqueous hydrochloric acid and then
extracted with t-butyl methyl ether, washed with brine, dried over magnesium
sulfate to give the crude acid. The acid was diluted with tetrahydrofuran
(500 mL) and methanol (50 mL), and triphenylphosphine (46 g, 176 mmol)
was added to the solution. To the mixture was added a solution of diisoporopyl
azodicarboxylate (40% in toluene, 90 mL, 178 mmol) over 5 min and the
resulting mixture was stirred for 1 hr at 08C. It was then concentrated under
reduced pressure, and the residue was chromatographed on silica gel with
ethyl acetate þ hexane (1 þ 4 by volume) as eluant to give a 93 : 7 mixture
of the methyl esters 1c and 1d (23.7 g, 80%) as a colorless oil. [a]2D4 þ 978
(c ¼ 2.5, CHCl3). NMR dH (CDCl3): 1.22 (3H, s), 1.26 (3H, s), 1.70 (3H, d,
J ¼ 5.1), 1.71 (1H, d, J ¼ 8.3), 1.98 (1H, t, J ¼ 8.3), 3.63 (3H, s), 5.6–5.7
(2H, m). IR nmax (neat): 2990, 1740, 1450, 1180 cm21. EIMS m/z: 168 (Mþ,
14), 153 (10), 109 (100).