42 
The  Origin  of  Fusel  Oil. 
I  Am.  Jour.  Pharni. 
l     January,  190fi. 
CH:t\, 
CH  .  CH2OH+NH3+C02. 
CH  .  CHNH2  .  COOH  +  H20 
C2H3/ 
C2H5/ 
Optically  active  ainyl  alcohol. 
Isoleucine. 
CH3\ 
CH3\ 
CH  .  CH2OH+NH3+C02. 
CH3/ 
Isobutyl  alcohol. 
CH  .  CHNH,  .  COOH+H20 
CH3/ 
Amidoisovaleric  acid. 
Fermentation  experiments  with  pure  sugar  and  pure  compressed 
yeast  showed  that  in  the  fermentation  upon  the  addition  of  leucine, 
inactive  amyl  alcohol,  or  on  the  addition  of  isoleucine  optically 
active  left-rotatory  amyl  alcohol  was  regularly  developed  in  amount 
equivalent  to  that  of  the  amidoacid  which  disappeared. 
If  r-leucine  is  fermented  with  sugar  and  yeast,  the  natural  /-leucine 
is  converted  by  the  yeast  into  amyl  alcohol,  while  the  ^-leucine 
remains  behind  almost  unacted  upon. 
The  writer  explains  from  the  foregoing  facts,  very  simply,  the 
formation  of  the  single  optically  active  constituent  of  fusel  oil, 
namely,  the  optically  active  amyl  alcohol  from  isoleucine  of  which 
one  asymmetric  carbon  atom  remains  unattacked.  Similarly,  just 
as  the  optically  active  amyl  alcohol  results  from  the  isoleucine, 
numerous  other  optically  active  compounds  are  derived  in  nature 
from  the  last  named  body,  as,  for  example,  with  certainty,  the  widely 
distributed  dextro-rotatory  valeric  acid. 
This  fusel-oil  formation  constitutes  a  new  and  very  peculiar 
breaking  down  of  albumen  or  of  the  amido-acids,  which  differs 
essentially  from  the  well-known  splitting  of  C02  from  the  amido- 
acids  in  putrefaction.  In  this  case  the  yeast  de-amidizes  the  amido- 
acids,  as,  for  example,  leucine  in  acid  solution,  by  the  action  of  a 
hydrolyzing  ferment  most  probably  at  first  to  the  corresponding 
oxyacid  leucic  acid,  which  then,  in  a  manner  analogous  to  the  forma- 
tion of  alcohol  from  lactic  acid  by  the  splitting  off  of  C02,  is  con- 
verted into  amyl  alcohol.  The  ammonia  molecule  which  is  set 
free  in  this  de  amidizing  is  used  by  the  yeast  for  albumen  formation. 
By  quantitative  experiments,  it  can  be  established  that  the  fusel-oil 
formation  corresponds  in  the  most  exact  way  with  the  building  up 
of  the  proteid  material  of  the  yeast,  and  for  the  conversion  of  a 
definite  amount  of  the  leucines  into  the  corresponding  amyl  alcohols, 
a  definite  amount  of  sugar  and  yeast  substances  is  necessary,  which 
later  becomes  enriched  thereby  with  nitrogen  to  a  certain  limit. 
The  writer  called  attention  finally  to  the  great  technical  import- 
