AmNov.r;i?sb9arm'}  The  Synthesis  of  Alkaloids.  547 
hydrogen  atoms  less  than  conine.    Of  these  bases,  smelling  like  con- 
ine,  the  first  and  third  are  strong  poisons. 
The  alkaloid  nicotine  C10HUN2  is  a  derivative  of  dipyridyl  C10H8N2 
and  apparently  hexahydrodipyridyl  C10H8(H6)N2.  The  two 
dipyridyls  known  (the  para  and  the  meta  compounds)  yield,  when 
reduced,  hexahydrodipyridyls  (isonicotine  and  nicotidine)  isomeric, 
but  not  identical  with  nicotine.  The  nicotinic  acid,  obtained  by  the 
oxidation  of  nicotine  with  chromic  or  nitric  acid,  or  with  potassium 
permanganate,  has  been  shown  to  be  simply  /9  pyridine-monocarb- 
oxylic  acid  C5H4N.COOH. 
If  we  turn  now  to  the  alkaloid  atropine  C17H23N03  which,  as  was 
known  as  long  ago  as  1863,  splits  up  into  tropine  C8H15NO  and  tropic 
acid  C9H10O3,  we  find  some  additional  results.  Tropine,  according  to 
Ladenburg,  is  a  substituted  tetrahydropyridine  containing  the  methyl 
(CH3)  and  the  oxethyl  (C2H4OH)  groups  in  place  of  two  H  atoms.  ^ 
Tropic  acid,  it  will  be  remembered,  has  been  identified  as  a  phenyl- 
oxypropionic  acid.  Now,  if  instead  of  tropic  acid  we  cause  to  com- 
bine with  the  tropine  another  aromatic  acid  we  get  a  tropeln,  of  which 
compounds  a  whole  class  have  been  obtained  analogous  in  constitution 
to  atropine.  Thus  benzoic  acid,  the  ortho,  meta,  and  para  oxyben- 
zoic  acids,  phenyl-acetic  acid,  the  two  isomeric  phenyl-glycollic  acids 
(of  which  one  is  called  mandelic  acid),  phthalic  acid,  and  cinnamic  acid 
have  all  been  combined  with  tropine  to  form  tropeine.  Of  these,  only 
one,  that  from  mandelic  acid  known  as  homatropine,  has  proven  physi-  * 
ologically  important.  Tropine,  decomposed  by  either  hydrochloric  or 
sulphuric  acids,  loses  a  molecule  of  water  and  yields  tropidine  C8H13N, 
which  has  also  been  shown  to  be  a  tetrahydropyridine  derivative  with 
methyl  (CH3),  and  ethenyl  or  vinyl  (C2H3)  as  the  replacing  groups. 
This  tropidine  is  a  liquid  base  with  a  conine-like  odor. 
The  acid  derivatives  of  pyridine  and  its  homologues  in  which  a 
nethyl  (CH3)  group  has  been  changed  into  the  carboxyl  group  (COOH) 
have  been  much  more  fully  investigated,  and  have  shown  in  some 
cases  unexpected  relations  to  natural  alkaloids.  Thus,  /9-pyridine- 
monocarboxylic  acid  has  already  been  spoken  of  as  nicotinic  acid ;  it 
is  also  produced  by  the  oxidation  of  pilocarpine ;  one  of  the  pyridine- 
dicarboxylic  acids  (cinchomeronic  acid)  is  found  in  the  oxidation  of 
the  natural  alkaloids,  cinchonine,  cinchonidine,  or  quinine.  This  is 
also  the  case  with  one  of  the  pyridine-tricarboxylic  acids  (carbocin- 
chomeronic  or  oxcinchomeronic),  which  may  be  obtained  by  the  oxi- 
