Approaches to the synthesis of cytochalasans. Part 6 . Synthesis of the C(14)–C(23) subunit of cytochalasins A, B. F and desoxaphomin

The synthesis of methyl (4 R , 8 R ,)‐10‐bromo‐8‐methyl‐4‐(1,3,6‐trioxaheptane)‐2‐deceneoate ( 5 ), a synthon for the construction of the macrocyclic moieties of the cytochalasins A ( 1), B. (2) F (3) and desoxaphomin ( 4 ) is described. ( S )‐Glutamic acid ( 6 ) was transformed to the C 5 ‐epoxide 10 and 3‐methylglutaric acid ( 11 ) to the C 5 ‐bromide 15 . Coupling of both 10 and 15 by a CuI‐catalyzed Grignard reaction gave the decanol 16 in very high yield. The latter was transformed by several steps to synthon 5 .