(5S,6R)-1-(2-(benzo[d][1,3]dioxol-5-yl)ethyl)-6-hydroxy-1-azaspiro[4.4]non-7-en-2-one

(5S)-1-[2-(3,4-methylenedioxyphenyl)ethyl]-1-azaspiro[4.4]non-7-ene-2,6-dione

(4S,5S)-2,3-didehydro-cephalotaxan-8-one

(6R)-7-[2-(3,4-methylenedioxyphenyl)ethyl]-1,4-dioxa-7-azadispiro[4.0.4.3]tridecan-8-one

(5R)-1-[2-(3,4-methylenedioxyphenyl)ethyl]-6-trimethylsilyloxy-1-azaspiro[4.4]non-6-en-2-one