A mixture of 1.0 g of the product from Example 1 and 2.2 g of tri-n-butylstannylazide in 30 ml of tetrahydrofuran was heated at reflux for 10 days. The reaction was allowed to cool to ambient temperature. A mixture of hydrochloric acid and methanol was added, and after stirring for 30 minutes, the mixture was concentrated in vacuo. The residue was purified by chromatography over silica gel eluting with a 30-75% ethyl acetate in hexane gradient which additionally contained 0.05% acetic acid. The appropriate fractions were cooled and concentrated to provide 592 mg of product. Recrystallization from hexane/ethyl acetate provided 580 mg of the desired title product.
