Synthetic studies towards oxazinins. An expedient first total synthesis and proof of the absolute stereochemistry of oxazinin-3

A synthetic strategy, based on intramolecular addition of an appropriate hydroxyl substituent to a 3-methyleneindolenine, towards the naturally occurring marine toxins oxazinin-1, -2 and -3 is presented. The expedient first total synthesis of oxazinin-3, thus accomplished, demonstrated the efficiency of the approach and established the absolute stereochemistry of oxazinin-3 as 2S,5S.