Photochemistry of sulphur-containing amino acids. Formation of thiophene derivatives

T@trahedronLettermlb

PergaaonFTOSS.

4, pp 343 - 344, 1973.

PHOTOCHEMISTRY

OF SULPHUR-CONTAINING

FORMATION

OF THIOPHENE

RintadiaQemtBritaiu.

AMINO ACIDS.

DERIVATIVES

H. Nishimura, T. Hansawa and J. Mizutani Department

of Agricultural

Chemistry,

Hokkaido

University,

Sapporo, Japan

(Reosivedin Japm 17 November19721 rsoeivsdin UK for plbliaatian2 JanWe

have studied the formation

ing amino acids oxygen-free

volatile

products from S-contain-

(precursors of onion and garlic flavour)

irradiated by y-rays in

aqueous solutions

trans rsomerlzation cysteine(PeCS) sulphrdes follows.

of

mechanism

in terms of food irradiation.

has been found from y-radlolysis

and it has been elucidated

1

Recently, a new cis-

of S-(cis-prop-l-enyl)-L-

that several cis- or trans-prop-1-enyl

as the mayor products are produced via prop-1-enyl

thiyl radicals as

2 ';";' CH$=C- S * w

CH+CH=S

The mayor products from W-photolysis y-radiolysis

in contrast

the comparisons

';' C&$=$-S* H

M

of PeCS are remarkably different

to the case of S-n-propyl-

between W

and y-ray, we wish to report on the identification

mechanism of the mayor products from W-photolysis

compounds

with biological

mM) dissolved

interest.

in triply-distilled

The oxygen-free

propyl prop-1-enyl

GC-,% and confirmed

compounds. 5 Alanine(large)

lamp.

2,4-(ca.l5%),3,4-

and 3-methylthrophene(5P)

mercaptan(40%),

sulphides(
of PeCS,4 one of S-

water was placed rn stoppered quartz tubes and

(7R), and 2,5-Dimethylthiophenes(
and

neutral solution of PeCS(20

irradiated for 20 hr using a 50 W low pressure mercury

derivatives

from

or S-allyl-k-cysterne. 3 In

formation

combined

1973)

di-prop-1-enyl

as other S-compounds

as

throphene

sulphides(
and R-

were characterized

by the

by comparing GLC and MS with those of reference

and cystine(trace)

etc. among the ninhydrrn-positive

products were identified by the two dimensional

TLC.

In the case of y-lrradi-

ation (lo'-106rad),

thaophene derivatives

high sensitive GLC.

From the results of ESR spectra(77.K)

343

could not be detected

even using the

of PeCS rrradlated

in

344

Ho. 4

aqueous system, anisotrooxc CH3CHXH-S*

radicals

(glE2.00, g2=2.02, g3=2.05) were 6 radrcals.

observed and the measured values agreed well with reference alkyl-thlyl These evidences

indicate that thiophene derivatives

thiyl radicals.

are produced via nrop-l-enyl

The yield of each of thlophene derivatives,

phldes and alanlne increased In narallel with irradiation ively and the oroportion of the yields of these products mately constant.

Though there is such a possibility

nes 1s produced by methyl scrambling of di-prop-l-enyl

hr), resoect-

in each time was anrroxl-

that each of dlmethylthiophe-

on the thlophene

ring or by the cycllzatlon

was produced from 3,4-dimethylthlophene(2)

irradiated for 5-20 hr.

dimethylthiophene

tlme(O-20

sul-

sulphides from r)V-Irradiated PeCS, only the trace amount of 2,4-

dxmethylthiophene(&) sulphrdes

H2S, mercaptan,

Therefore,

these facts lndlcate that each of

is derived through the Independent

mechanism for dimethylthiophene

formation

or di-prop-1-enyl

pathway.

is sugoested

The reasonable

tentatively

as follows.

1,3-shift CHeH-al CH3CH%H=S I CH3CH-CH=s I

3&3-shift

)

Thlyl radicals(A and 2) and alkyl radical(z) attack of PeCS to produce 4 and z, via 1,3-prototropic

shift glvc 2 and sand

14~5 leads to stable &, and 2, respectively. yield, 2,5-dimethylthiophene &*

Moreover,

unstable

the immediate elimination

Because of trace amounts

In the

might have been produced by methyl scrambling

3-methylthioqhene

of

from

might be produced through the internedtate

formed by 1,3-methyl shift of 4_ and also through the methyl elil*inatxon of s or 2, though the yield of 3-methylthiophene REFEFENCES l)H.Nishimura, J.Mrrutan~,

S.Kawakishi

ano V.Namiki, Agr.Biol.Chem., &609(1970),ll.\ishimura,

Y.Cbata and ~~.Namiki,Tetrahedron,2~,307(1971).

Mizutanl, J.C.S.Chem.Comm., disulphide

from 2 or 2 was trace. AND REQ"ARUS

73P(1972).

3)D1-;-propyl

were produced from S-n-nropyl-k-cysteine,

2)H.Nishimura

and J.

sulphlde and dl-;-propyl and diallyl sulphlde, a-

propyl ally1 sulphide and ally1 alcohol were produced from S-allyl-&-cysleine W-or

y-Irradiation.

synthetic

procedure of Carson and Wong; J.F.Carson

1764(1963). analysis.

4)S-(CA-prop-1-enyl)-L-cystelne(PeC5)

5)Rrference compds.were

confirmed

and F.F.Wony. Chem.ana

,&,ZpPP(

1966).

Tnd.,

by GLC,Eb, N II'and elementai

6)Y.'
Sanner, Acta Chem.Scand.

by

was prepared by the

T.Henrrksen

and 1.