2) AC20, DMAP Et3N

2) AC20, DMAP Et3N

Scheme 4 Oritani's synthesis of streptovitacin A and E-73

enolate as shown in Scheme 1, the product ratio became 18/a-epi-18+6-epi-18 = 35 : 65. These isomers were hardly separable but pure samples were provided by HPLC and recrystallization. Compound (±)-18 was converted to E-73 [(±)-21] in three steps [22]. Only (±)-18 showed a weak growth inhibitory activity against S. cerevisiae [21,22].

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