204
G. L. CANTONI
corresponding pyridone are also important products in the metabolism
of the amino acid tryptophan, but this is not the case in other mammals such as dogs, cats, and rats (105).
IV. Sulfonium Compounds
From a chemical point of view sulfonium compounds as a group
may be considered analogous to the quaternary nitrogen compounds. It
is interesting to observe that although sulfonium compounds had been
known to chemists for almost 100 years, and quaternary ammonium
compounds have been recognized in nature for the same length of
time, sulfonium compounds have not been known to occur biologically
or to play a part in intermediary metabolism until quite recently. At
the present time only 3 sulfonium compounds have been found to occur
naturally: dimethylpropiothetin, S-adenosylmethionine, and S-methylmethionine. It is of interest that the suggestion that sulfonium compounds might play a part in biological processes (106) anteceded the
isolation of such compounds from naturally occurring materials.
A. NATURAL OCCURRENCE AND CHEMISTRY
1.
Dimethylpropiothetin
The first* demonstration of the natural occurrence of sulfonium
compounds was the outcome of a search for the precursor of the dimethylsulfide which is evolved from certain marine algae.
Challenger and Simpson (109) isolated dimethylpropiothetin
(CH 3 ) 2 —S—CH 2 —CH 2 —COOfrom Polysiphonia lanosa, and conclusively proved that this sulfonium
compound was the precursor of the evolved dimethylsulfide. Formation
of dimethylsulfide and acrylic acid on alkaline treatment of dimethylpropiothetin had been reported earlier by Holmberg (110) and alkaline fission of sulfonium compounds is generally well known. Since liberation of dimethylsulfide from P. lanosa is associated with exposure of
the algae to environmental changes (air, distilled water, or detachment
from its host, Ascophyllum nodosum) but is not noticed after immer* Neuberg and Grosser (107) in 1905 tentatively identified as methyldiethylsulfonium hydroxide a compound from dog urine capable of evolving diethylsulfide
on mild warming with alkali. However, authentic methyldiethylsulfonium hydroxide
does not decompose to diethylsulfide with warming in NaOH and even at 100°,
it cleaves primarily to methylethylsulfide (108). Thus, the exact identity of the
compound described by Neuberg and Grosser remains to be established.
G. L. CANTONI
corresponding pyridone are also important products in the metabolism
of the amino acid tryptophan, but this is not the case in other mammals such as dogs, cats, and rats (105).
IV. Sulfonium Compounds
From a chemical point of view sulfonium compounds as a group
may be considered analogous to the quaternary nitrogen compounds. It
is interesting to observe that although sulfonium compounds had been
known to chemists for almost 100 years, and quaternary ammonium
compounds have been recognized in nature for the same length of
time, sulfonium compounds have not been known to occur biologically
or to play a part in intermediary metabolism until quite recently. At
the present time only 3 sulfonium compounds have been found to occur
naturally: dimethylpropiothetin, S-adenosylmethionine, and S-methylmethionine. It is of interest that the suggestion that sulfonium compounds might play a part in biological processes (106) anteceded the
isolation of such compounds from naturally occurring materials.
A. NATURAL OCCURRENCE AND CHEMISTRY
1.
Dimethylpropiothetin
The first* demonstration of the natural occurrence of sulfonium
compounds was the outcome of a search for the precursor of the dimethylsulfide which is evolved from certain marine algae.
Challenger and Simpson (109) isolated dimethylpropiothetin
(CH 3 ) 2 —S—CH 2 —CH 2 —COOfrom Polysiphonia lanosa, and conclusively proved that this sulfonium
compound was the precursor of the evolved dimethylsulfide. Formation
of dimethylsulfide and acrylic acid on alkaline treatment of dimethylpropiothetin had been reported earlier by Holmberg (110) and alkaline fission of sulfonium compounds is generally well known. Since liberation of dimethylsulfide from P. lanosa is associated with exposure of
the algae to environmental changes (air, distilled water, or detachment
from its host, Ascophyllum nodosum) but is not noticed after immer* Neuberg and Grosser (107) in 1905 tentatively identified as methyldiethylsulfonium hydroxide a compound from dog urine capable of evolving diethylsulfide
on mild warming with alkali. However, authentic methyldiethylsulfonium hydroxide
does not decompose to diethylsulfide with warming in NaOH and even at 100°,
it cleaves primarily to methylethylsulfide (108). Thus, the exact identity of the
compound described by Neuberg and Grosser remains to be established.