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Compound 7 was dissolved in tetrahydrofuran (120 ml) and cooled in an ice bath. Diazomethane was generated by addition of N-nitrosomethylurea to an ice cold, equivolume mixture of ether and 40% aqueous potassium hydroxide. The diazomethane solution was added without purification to the stirred solution of the amino acid derivative. The reaction was complete when N2 was no longer evolved upon addition of diazomethane. Excess diazomethane was consumed by the addition of acetic acid. The solution was extracted successively with saturated saline, 1M sodium bicarbonate, 0.1M HCl, and again with saline and dried (MgSO4). Evaporation left 3.56 g (88.4%) of a solid melting at 110°-112° C. which was pure by TLC (chloroform/methanol acid: 85/10/5). [α]D25 =-13.8 (c=2.1, ethanol)

1. temperaturecooled in an ice bath
2. customExcess diazomethane was consumed by the addition of acetic acid
3. extractionThe solution was extracted successively with saturated saline, 1M sodium bicarbonate, 0.1M HCl
4. dry with materialagain with saline and dried (MgSO4)
5. customEvaporation
6. waitleft 3.56 g (88.4%) of a solid melting at 110°-112° C. which