1,6-Dihydro-3(2H)-pyridinones. V. Total synthesis of (.+-.)-eburnamonine.

3-Ethyl-3-methoxycarbonylmethylpiperidine (20) was prepared via the unsaturated aldehyde (12) derivel from benzyl 1, 6-dihydro-3 (2H)-pyridinone-1-carboxylate (5b). N-Chlorination of 20 and subsequent exposure to a base afforded rel-(2S, 3R)-3-ethyl-2-hydroxypiperidine-3-acetic acid γ-lactone (3) in a good yield. According to the known method, the lactone (3) was converted into (±)-eburnamonine (1) and (±)-epieburnamonine (31). A possible pathway from 20 to 3 is also discussed.