Studies Directed Toward the Synthesis of the Type a Streptogramin Antibiotics

The streptogramin antibiotics occur naturally as mixtures of two types of components, A and B (or alternatively M and S). 1–5 Structures are presently known for six type A components (1-6) as shown on the next page. Stereochemistry has not been determined rigorously in all cases. Confusion arises over nomenclature in this area because of the several different names that these compounds have been given. As an example, compound 1 has been named virginiamycin M1, mikamycin A, streptogramin A, ostreogrycin A, synergistin A-1, PA 114 A1, vernamycin A, pristinamycin IIA, and staphylomycin M1. For comparison purposes, virginiamycin S1 (7) is shown as a representative type B component. Our synthetic work has been focused solely upon the type A compounds.