Synthesis of Cyclosporine. I. Synthesis of enantiomerically pure (2 S ,3 R ,4 R ,6 E )‐3‐hydroxy ‐4‐methyl‐2‐methylamino‐6‐octenoic acid starting from tartaric acid

Starting from R , R ‐(+)‐tartaric acid, the synthesis of (2 S ,3 R ,4 R 6 E )‐3‐hydroxy ‐4‐methyl‐2‐methylamino‐6‐octenoic acid in 24 steps is reported. This novel amino acid is found in the cyclic undecapeptide cyclosporin A, isolated from the fungal strain Tolypocladium inflatum GAMS . Its stereospecific synthesis allowed, for the first time, the isolation and characterization of the new amino acid previously reported as the ‘C‐9‐amino acid’ [1].