- pi per id yl - prop al de hy de ) ▁corresponding ▁to ▁con i ine , ▁and ▁yield ed ▁rac - con i ine ▁when ▁its ▁hyd ra zone ▁was ▁he ated ▁with ▁sod ium ▁eth ox ide ▁in ▁eth an ol ▁at ▁ 1 5 6 – 1 7 0   ° C . ▁According ▁to ▁these ▁authors , ▁D -( S )- con i ine ▁is ▁rendered ▁almost ▁opt ically ▁in active ▁when ▁he ated ▁with ▁b arium ▁hydro x ide ▁and ▁alco hol ▁at ▁ 1 8 0 – 2 3 0   ° C . ▁Le it he ▁has ▁shown ▁by ▁observation ▁of ▁the ▁optical ▁rotation ▁of ▁(+ )- pipe col ic ▁acid ▁( pi per id ine - 2 - car box y lic ▁acid ) ▁and ▁some ▁of ▁its ▁derivatives ▁under ▁varying ▁conditions , ▁that ▁it ▁must ▁belong ▁to ▁the ▁D - series ▁of ▁am ino ▁ac ids . ▁ ▁B ios yn thesis ▁ ▁The ▁complete ▁b ios yn thesis ▁of ▁con i ine ▁is ▁still ▁being ▁investig ated . ▁ ▁While ▁the ▁exact ▁mechanism ▁is ▁still ▁to ▁be ▁determined , ▁much ▁of ▁the ▁path way ▁has ▁been ▁el uc id ated . ▁ ▁Origin ally ▁thought ▁to ▁use ▁ 4 ▁ac et yl ▁groups ▁as ▁feed ▁comp ounds ▁for ▁the ▁poly ket ide ▁synth ase ▁that ▁forms ▁con i ine , ▁recent ▁work ▁has ▁led ▁to ▁the ▁conclusion ▁that ▁two ▁mal ony l ▁and ▁a ▁but y ry l ▁Co A ▁are ▁what