General
Solvents used for open column chromatography and low pressure liquid chromatography
(LPLC) were distilled from technical grade solvents. The other organic
solvents were HPLC grade. HPLC grade water was obtained from a Seralpur Delta
water purification system. TLC was carried out on silica gel F254 precoated Al
sheets (Merck, Darmstadt). Silica gel (40–63 mm) for column chromatography was
from Macherey & Nagel (Du¨ren, Germany).