The product obtained in Example 29 (3.1 g) and the product obtained in Example 15 (4.3 g) were dissolved in anhydrous dichloromethane (200 ml) with stirring, the faint yellow solution was cooled to -30° C., and a solution of dicyclohexylcarbodiimide (1.2 g) in anhydrous dichloromethane (30 ml) was dropwise added over a period of five minutes. The resulting faint yellow solution was allowed to stand at 0° C. for nine hours, the colorless crystals separated were removed by filtration, and the filtrate was washed with 50 ml of 1N aqueous citric acid, 50 ml of saturated sodium bicarbonate solution and 80 ml of saturated sodium chloride solution in that order and dried over anhydrous sodium sulfate. The dried filtrate was concentrated in vacuo, the yellow, viscous residue (6.8 g) was purified by silica gel column chromatography using ethyl acetate/n-hexane as eluent, yielding 5.3 g of the objective compound as faint yellow crystals.
