Zur Biogenese der Makrolide

Abstract

Further investigation of the biosynthesis of magnamycin (I) shows that other precursors besides acetate and propionate participate in the formation of the lactone ring of I. These precursors, which can be more easily formed from glucose or succinic acid than from acetate, take part in the formation of the C-atoms 1 to 8. This conclusion is based on the following results: a) With acetate-1- or -[2-14C] as the precursor the activity found in different degradation products of I corresponds to the incorporation of only 7 acetate units. b) Glucose-[U-14C] and -[3.4-14C] are predominantly incorporated into C-1 to C-11 of the lactone (C12-acid). Further degradation to the C8-acid (C-5 to C-11) shows that the activity of glucose-[3.4-14C] is located almost exclusively in C-1 to C-4. This finding is not consistent with earlier results and cannot be satisfactorily explained at the moment. c) With succine acid-1.4- and -[2.3-14C] as precursors up to 80% of the activity is located in the C12-acid. The distribution of activity in L-mycarose and -ᴅ-mycaminose with glucose-3.4- and -[6-14C] as precursors confirms the conclusion drawn earlier that these sugars are formed from D-glucose without an intermediate breakdown and in addition excludes the possibility of an inversion of the hexose chain during the biosynthesis. With methionine-[methyl-14C] as the precursor the activity is evenly distributed between the C-methyl group at C-3 of mycarose, the dimethylamino group of mycaminose and the O-methyl group of the lactone.