General Experimental Procedures. Melting points are uncorrected.
Optical rotations were measured using a Horiba Sepa-200 polarimeter.
IR spectra were recorded on a Shimadzu FTIR-4200 infrared spectrometer.
1
H and 13C NMR spectra were measured with a Varian Unityplus
instrument at 500 and 125 MHz. 1
H NMR assignments were
determined by 1
H-1
H COSY experiments. 13C NMR assignments were
determined using DEPT, HMQC, and HMBC experiments. HRFABMS
were recorded on a JEOL JMS-HX110 instrument, and HREIMS and
HRESIMS were recorded on a JEOL JMS-700TZ instrument. Silica
gel 70-230 mesh was employed for column chromatography and silica
gel 230-400 mesh for flash column chromatography. HPLC separations
were performed on a Hitachi L-6200 HPLC instrument with an Inertsil
Prep-sil GL 10 × 250 mm stainless steel column and an Inertsil PrepODS
GL 10 × 250 mm stainless steel column and monitored by a
Hitachi L-7400 UV detector and a Shodex SE-61 RI detector