▁ 2 3 7 a ▁and ▁ 2 3 8 a ▁are ▁the ▁same ▁comp ound ▁as ▁both ▁are ▁the ▁parent ▁for ▁either ▁series ▁with ▁a ▁hydro gen ▁s atur ated ▁in ▁their ▁respective ▁substitution ▁place . ▁ ▁Direct ▁ 2 , 3 - py rim id ino ▁f used ▁▁ ▁c f . ▁st rob am ine ▁( at ▁right ) ▁for ▁a ▁more ▁eff ica cious ▁comp ound ▁as ▁like ▁the ▁below . ▁ ▁" NA " ▁= ▁" no ▁aff inity ", ▁e . g . ▁un quant ifiable . ▁ ▁Direct ▁di - h eter o - ben z ene ▁( py rim id ino ) ▁ 2 , 3 - f used ▁and ▁thus ▁rig id ified ▁c oca ine ▁anal ogs . ▁ ▁Pi per id ine ▁c oca ine - hom olog ues ▁ ▁c f . ▁ph eny lt rop ane ▁pi per id ine - hom olog ues ▁for ▁comp ounds ▁with ▁a ▁more ▁optimized ▁con formation ▁that ▁yield ▁higher ▁aff in ities ▁when ▁binding ▁to ▁M AT . ▁ ▁C oca ine ▁ha pt en ▁analog ues ▁▁ ɑ 6 -( 2 R , 3 S )- 3 -( ben zo y lo xy )- 8 - m eth yl - 8 - az ab icy clo ▁[ 3 . 2 . 1 ] ▁oct ane - 2 - car b ony lo xy - hex ano ic ▁acid ▁b 6 -( 2 R , 3 S )- 3 -( ben zo y