THE STRUCTURES OF THE m-CHLOROPERBENZOIC ACID OXIDATION PRODUCTS OF 8, 9-ANHYDROERYTHROMYCINS A-AND B-6, 9-HEMIACETAL AND OF (8S)-8-HYDROXYERYTHROMYCIN B

13C-NMR studies have confirmed the structures of (8S)-8-hydroxyerythromycins A- and B-6, 9;9, 11-acetal proposed by KROWICKI and ZAMOJSKI2, 3) for the products of the m-chloroperbenzoic acid oxidation of 8, 9-anhydroerythromycins A- and B-6, 9-hemiacetal. The preparations of (8S)-8-methylthiomethoxy- and (8S)-8-methoxyerythromycin B-6, 9;9, 11-acetals are described. The latter are stable in aqueous acetic acid under conditions which convert (8S)-8-hydroxyerythromycin B-6, 9;9, 11-acetalinto (8S)-8-hydroxyerythromycin B. In a paper describing the preparation of the C8-epimeric 8-hydroxyerythromycins B, we reported1) that buffered m-chloroperbenzoic acid oxidation of 8, 9-anhydroerythromycin B-6, 9-hemiacetal (1), followed by catalytic reduction of the resulting N-oxide to the free amine, gave (8S, 9S)-8, 9-anhydroerythromycin B-6, 9-hemiacetal-8, 9-epoxide (2). Our assignment of structure 2 was based on the expected course of olefin epoxidation with peracids and with apparently compatible spectral properties. In addition, the facile conversion of 2 to (8S)-8-hydroxyerythromycin B (3) in aqueous acetic acid was expected for the strained epoxy spiroacetal structure (2).