326
Sacolick and Curley
5
column chromatography on silica gel (5% ethyl acetate/hexane, followed by 10% ethyl
acetate/hexane) .
Scheme 1
Experimental Section
All solvents and reagents were purchased as reagent grade from Sigma-Aldrich (Milwau-
kee, WI) and were used as obtained. Reactions were performed in oven-dried glassware
under an argon atmosphere and gold fluorescent lights. Analytical TLC was acquired on sil-
ica gel 60 F254 aluminum-backed plates from Merck (Darmstadt, Germany). Flash column
chromatography was carried out on silica gel 60 (230–400 mesh) from Merck. Analysis
by HPLC was performed on a Beckman Instruments unit (model 127 pump, model 166
detector) using 1 mL/min of 90% MeOH-H2O through a Polaris C18 column with monitor-
1
13
ing at 360 nm. H and C NMR spectra were recorded in CDCl3 on a Bruker Instruments
1
DRX400 spectrometer (Billerica, MA) operating at 400 MHz for H measurements. Elec-
trospray mass spectra were measured on a Micromass QTOF mass spectrometer in the Ohio
State University Campus Chemical Instrument Center.
Procedure
To a stirred solution of 1 (5.10 g; 15.5 mmol) in 500 mL of anhydrous methanol was added
sodium pieces (0.39 g; 1.1 equiv.) and the mixture stirred for 40 minutes at which time TLC
(20% ethyl acetate/hexane) indicated complete consumption of 2. The solution was passed
through Amberlite IRA-400 ion-exchange resin (6.5 g; chloride form) and the column was
rinsed with methanol. The eluent was concentrated under reduced pressure to a red oil
which was dissolved in the minimum amount of dry dichloromethane (2–3 mL). After
addition of activated MnO2 (33.0 g; 24.4 equiv.) and dry ethyl acetate (40 ml dried over 4
˚
A molecular sieves), the thick suspension was stirred for 5 hrs at which time TLC indicated
complete oxidation to 1. After filtration of the solution through a pad of diatomaceous earth
and rinsing with dichloromethane, the filtrate was evaporated in vacuo to give 2 (3.75 g,
◦
6
◦
8
(
1
5%) as a yellow-orange solid, mp. 57.5–60 C (lit. mp. 57 C); HPLC: tR = 10.3 min
1
∼96%). H NMR (CDCl3): δ 0.93 (s, 6H, CMe2), 1.36 (m, 2H, CH2), 1.51 (m, 2H, CH2),
.61 (s, 3H, CH3), 1.90 (m, 2H, CH2), 1.91 (s, 3H, CH3), 2.20 (s, 3H, CH3), 5.83 (d, 1H, J
=
8 Hz, 14-CH), 6.03–6.25 (m, 4H, vinyls), 7.03 (dd, 1H, J = 11.6 and 14.9 Hz, 12-CH),
13
9
.97 (d, 1H, J = 8 Hz, CHO). C NMR (CDCl3): δ 13.6, 13.7, 19.9, 22.4, 29.7, 33.8,
34.9, 40.3, 129.7, 130.19, 130.21, 130.96, 133.1, 135.3, 137.8, 138.3, 141.7, 155.1, 191.3.
+
HRMS (ESI): m/z [M + Na] : Calcd for C20H28O + Na: 307.2038. Found: 307.2040.