Scheme 11.
(A) Platinum-catalyzed intramolecular [3 + 2] cycloaddition of propargylic ketal derivative 142 to give indoline 143 [67]. (B) The proposed catalytic mechanism. (C) The completion of total synthesis of kopsanone (19).
(A) Platinum-catalyzed intramolecular [3 + 2] cycloaddition of propargylic ketal derivative 142 to give indoline 143 [67]. (B) The proposed catalytic mechanism. (C) The completion of total synthesis of kopsanone (19).