A.m.  Jour.  Pharm.  i 
January,  1906  I 
The  Origin  of  Fusel  Oil. 
41 
The  view  that  has  prevailed  generally  since  the  time  of  Pasteur 
to  the  present,  in  connection  with  chemistry  of  fermentation  and  the 
origin  of  fusel  oil  was  that  fusel  oil,  or  more  especially  its  most  im- 
portant constituent,  amyl  alcohol,  was  formed  in  the  fermentation 
from  the  sugar,  by  the  action  of  bacteria,  a  view  which  seemed  also 
to  be  confirmed  by  the  more  recent  researches  of  Kruis  and  Ray- 
man,  Emmerling  and  others.  At  the  same  time,  it  never  had  been 
found  possible,  even  with  the  aid  of  fusel-oil-forming  bacteria  which 
are  found  abundantly  in  nature,  to  produce  fusel  oil  or  amyl  alcohol 
under  the  conditions  of  a  normal  fermentation. 
The  writer  points  out  that  all  the  theories  hitherto  held  with 
regard  to  the  fusel-oil  formation  have  rested  upon  false  premises  and 
goes  on  to  show  that  fusel  oil  in  the  ordinary  fermentation  is  pro- 
duced not  from  the  sugar,  but  from  the  products  of  decomposition 
of  proteid  matter,  such  as  the  amido-acids,  and,  moreover,  not  by 
the  action  of  bacteria,  but  under  the  influence  of  the  vital  activity 
of  the  yeast  itself.  The  clue  to  this  conclusion,  based  upon  a  long 
series  of  experiments,  was  given  by  the  discovery  of  isoleucine, 
which  the  writer,  somewhat  more  than  two  years  ago,  found  in  the 
last  residues  of  the  sugar  industry,  a  strontian  molasses  residue,  and 
which  he  subsequently  has  recognized  as  a  most  important  product 
of  decomposition  occurring  in  all  albumenoids  along  with  leucine. 
This  isoleucine  has  shown  itself  in  its  constitution  to  be  the  first 
of  the  so-far  known  amido-acids  with  two  asymmetric  carbon  atoms, 
of  which  the  one  is  formed  by  the  splitting  of  the  carbon  chain,  and 
is,  therefore,  a  methyl-ethyl-amidopropionic  acid  of  the  formula 
^CH  .  CHNH2  .  COOH, 
QH5/ 
which  stands  in  close  relation  to  the  optically  active  amyl  alcohol, 
which  latter  can  be  built  up  from  this  by  means  of  the  aldehyde,  the 
cyanhydrin  reaction  and  saponification.  That  similar  relations  exist 
between  the  ordinary  leucine  and  isoamyl  alcohol,  is  shown  in  the 
following  reactions,  which,  without  further  explanation,  indicate  the 
origin  of  this  most  important  constituent  of  fusel  oil. 
CH8\        *  CH3\ 
CH  .  CH2CHNH2  .  COOH  +  H.,0  CHCH,  .  CFT,OH  +  NH.,-f  CO,. 
CH;1/  CH:i/ 
Leucine.  Isoamyl  alcohol. 
