Fentanyl 3-propyl

The l-methyl-3-allyl congener of fentanyl was made by application of the routine synthesis to l-methyl-3-allyl-4-piperidone (p.267) while l-carbethoxy-3-allyl-4-piperidone served as intermediate for synthesis of the 3-allyl/propyl-N-phenethyl analogs (Scheme 8.1). Reduction of intermediate Schiff bases was highly stereoselective and the cis isomers were produced almost exclusively by both chemical and catalytic reduction procedures low yields of the 3-propyl... 

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