 Butadiene 1 reacts in an asymmetric Diels-Alder reaction with the esterification product of acrylic acid and 2,2,2-trifluoroethanol 2 catalysed by the CBS catalyst.The ester 3 is converted into an amide in 4 by reaction with ammonia and the next step to lactam 5 is an iodolactamization with iodine initiated by trimethylsilyltriflate.The amide group is fitted with a BOC protecting group by reaction with Boc anhydride in 6 and the iodine substituent is removed in an elimination reaction with DBU to the alkene 7.