546 
The  Synthesis  of  Alkaloids. 
Am.  Jour.  Pharm. 
Nov.,  1889. 
second  of  these  two  classes,  and  to  define  as  alkaloids  "  those  organic 
bases  found  in  the  plant  kingdom,  which  are  pyridine  derivatives," 
and  we  doubt  not  that  this  will  be  the  gradual  practice  as  the  differ- 
ent plant  bases  become  more  fully  studied. 
Quite  an  additional  amount  of  literature  on  this  subject  has  accu- 
mulated within  the  last  six  years,  and  we  will  therefore  briefly  refer 
to  some  of  these  newer  results.  First,  clearer  ideas  of  the  general 
underlying  compounds  have  been  obtained.  It  has  been  seen  that 
these  compounds,  pyridine  C5H5lSr,  quinoline  C9H7N,  and  acridine 
C13H9N  correspond  to  benzene  C6tJ6,  naphthalene  C10H8  and  anthra- 
cene C14H10,  and  have  analogous  relations  with  each  other ;  that  the 
stability  and  behavior  towards  reagents  of  analogous  derivatives, 
for  instance  of  benzene  and  pyridine,  exactly  correspond  ;  that  the 
reducibility  of  the  molecules  is  perfectly  analogous.  As  from  ben- 
zene hexahydrobenzene  is  obtained,  so  from  pyridine  hexahydropyri- 
dine,  as  from  naphthalene  tetrahydronaphthalene  is  obtained,  so  from 
quinoline  tetrahydroquinoline,  as  from  anthracene  dihydro-anthracene, 
so  from  acridine  dihydro-acridine.  These  are  also  in  each  case  the 
most  stable  of  the  hydrogen  addition  products. 
Of  the  derivatives  of  pyridine,  one  of  the  simplest  and  best  studied 
is  hexahydropyridine,  or  piperidine  as  it  proves  to  be.  It  can  be 
formed  from  piperine,  the  alkaloid  of  pepper,  direct  from  pyridine  by 
the  action  of  reducing  agents,  or  as  Ladenburg  has  shown,  from 
pentamethylene  diamine. 
Conine,  the  alkaloid  of  hemlock,  which  in  my  previous  lecture  I 
said  was  probably  derived  from  propyl-piperidine,  has  since  been  made 
synthetically  by  Ladenburg  and  its  nature  and  derivation  clearly 
shown.  It  is  the  dextro-rotatory  a  normal  propyl-piperidine.  In 
obtaining  it,  pyridine  is  first  converted  into  a  allyl-pyridine,  which 
reduced  by  sodium  in  alcoholic  solution  yields  an  optically  inactive  a 
normal  propyl-piperidine.  The  tartrate  of  this  base  is  made  and  crys- 
tallized when,  following  the  analogy  of  the  splitting  of  racemic  acid 
into  dextro-rotatory  and  lsevo-rotatory  tartaric  acid,  we  get  a  dextro 
and  a  lsevo  conine,  of  which  the  first  is  the  true  alkaloid  of  the  hem- 
lock. The  inactive  conine  can  also  be  made  synthetically  from 
conyrin,  or  a  normal  propyl-pyridine,  by  reduction  with  hydrogen 
iodide,  or  from  cony dr in  (oxy conine),  which  occurs  in  hemlock  along 
with  conine.  A.  W.  Hofmann  has  obtained  three  isomeric  bases,  a, 
ft,  and  y  coniceln  of  the  formula  C8H15N,  and  hence  containing  2 
