Methylierungs‐Reaktionen an 30‐Oxa‐[14]cytochalasanen

For synthetic studies the protection of the hydroxyl groups of phomin (cytochalasin B) ((7 S ,22 R ,26 R )‐7,26‐dihydroxy‐22‐methyl‐30‐oxa‐[14]cytochalasa‐6(18), 19 t 27 t ‐trien‐1,29‐dion) ( 1 ), the dodecahydro‐derivative 2 , and the dihydro‐derivative 4 by methylation was investigated. Treatment of 1 with CH 3 I/Ag 2 O gave the iminoether 6 . The reaction of 4 with CH 2 N 2 /BF 3 led to the di‐O‐methyl derivative 8 and to the N‐methyl‐di‐O‐methyl derivative 9 , whereas 2 was transformed to the N‐methyl‐di‐O‐methyl compound 10 and to the iminoether 11 . NaBH4 reduction of 3 yielded not only 4 but also the epimeric dihydro derivative 5 .