CHEMISTRY OF THE ANNONACEAE .29. STRUCTURE OF MEZZETTIASIDE-2, MEZZETTIASIDE-4, MEZZETTIASIDE-5, MEZZETTIASIDE-6 AND MEZZETTIASIDE-7, NEW PARTIALLY ESTERIFIED 1-O-OCTYL TRI-RHAMNOSYL AND TETRA-RHAMNOSYL DERIVATIVES FROM MEZZETTIA-LEPTOPODA

Extensive NMR and MS studies have led to the characterization of mezzettiasides-2, -4, -5, -6 and -7 from the stem bark of Mezzettia leptopoda (Annonaceae). All mezzettiasides isolated to date are based on an octyl 4-O-acetyl-alpha-L-rhamnopyranosyl-(1 --> 3)-2,4-di-O-acetyl-alpha-L-rhamnopyranosyl-(1 --> 3)-4-O-hexanoyl-alpha-L-rhamnopyranoside nucleus (= mezzettiaside-4). Mezzettiaside-2 has an additional O-acetyl substituent at C-2 of the terminal hexose and mezzettiasides-5 to -7 an additional 1 --> 3-linked alpha-L-rhamnose unit at C-3 of that hexose (= mezzettiaside-7). Mezzettiaside-5 has C-3 of the additional hexose unit O-acetylated; in mezzettiaside-6 C-2 of that unit is O-acetylated