Dec. 5 , 1959
NEW METABOLITE OF DOPAMINE AND DERIVATIVES
were filtered and washed with a small volume of cold 48% hydrobromic acid. There was obtained 650 mg. (95.5%), m.p. 218-219". The substance gave a single spot on paper in several solvent systems (Table 111). The ferric chloride (mp): 297 ( € 4,700). test gave a brown color; Anal. Calcd. for CsHI,N08.HBr: C, 38.41; H, 4.84; N, 5.60. Found: C, 38.42; H, 5.08; N, 5.60.
6231
Achowledgment.-We are indebted to Dr. Albert Sjoerdsma and &fr. C. R. Creveling, National Heart Institute!for assistance in the pharmacological and spectrofluorometric tests for norepinephrine* BETHESDA 14, MD.
[ C ~ N T R I B U TFROM ~ O NTHE NATIONAL INSTITUTEOF ARTHRITIS AND METABOLIC DISEASES, NATIONAL INSTITUTES OF HEALTII, SERVICE] PUBLIC HEALTH
Formation and Rearrangements of Aminochromes from a New Metabolite of Dopamine and Some of its Derivatives' B Y SIROSENOII~ AND BERNHARD WITKOP RECEIVED MAY15, 1959 Spectrophotometric, polarographic and tritium studies demonstrate the easy oxidative cyclization of 2,4,5-trihydroxyphenethylamine ( I ) , the new metabolite from dopamine, to the p-quinoid aminochrome IV, while 2-methoxy-4,5-dihydroxyphenethylamine (VII) goes to the o-quinoid aminochrome which is easily rearranged to the dihydroxyindole VIII. The low oxidation-reduction potential of I ( E l / , +0.083 v.) is indicative of a p-quinoid oxidation product I1 whereas El/, +0.172 v. of the methoxydopamine VI1 is characteristic of an o-quinoid oxidation product. The amine I containing two tritium atoms in the benzyl position of the side chain retained all activity on cyclization to the final product, the aminochrome IV, whereas the analogously tritium-marked VI1 lost as required one atom of tritium in the conversion to the indole VIII. The ( X I I a ) via the crystalline aminochrome X I I I a to 4-methconversion of 2-methoxy-3-bromo-4,5-dihydroxyphenethylamine oxy-bbromo-6,7-dihydroxyindole(XIV) extended and confirmed these observations and established the position of the bromine in the starting amine.
The oxidation products of catecholamines, among them the so-called aminochromes,a are of importance in the determination of (n~r)epinephrine.~ So far they have no clear physiological role,6 no significant pharmacological effects and only minor OH "*" therapeutic applications.6 I, A%": 295, e 4,700 The easy oxidation or metabolic conversion of dopamine to 2,4,5-trihydroxyphenethylamine(I) adds to the recent interest in (dihydro)-indoles with oxygen functions in position 4,' 6 and 7a which would arise by intramolecular oxidative cyclization I30 O H of the ethaneamine side chain (I-VI). The reversible polarographic half-wave (oxidation-reduction) potentials bf these amines can be determined without interference of the side chain, since any possible intramolecular addition would be too slow to be ~ignificant.~Compound I has a much lower oxidation-reduction potential (Ell, 0.083 v.) than its methoxy derivative VI1 (,?31/~ 0.172 v.) which is incapable of forming a fi-quinone, reminiscent of the similar case IX e X (R = H or CH3) lo where the oxidation-reduction potentials of
IT
1
&
+ +
(1) Oxidation Mechanisms. XXIII. Preceding paper, cf. THIS JOURNAL, S i , 6222 (1959). (2) Visiting Scientist of the USPHS on leave of absence from the Institute of Food Chemistry and Osaka City University, Japan. (3) H. Sobotka and J. Austin, THISJOURNAL, 73, 3077 (1951). (4) A. Lund, Acfa Pharm. T o x . , 6 , 75, 121 (1949); 6, 137 (1950); U. S. v. Euler and J. Floding, Acfa Phrsiof. Scond., SS, Suppl. 118, 45 (1966). (5) Adrenochrome, c.g., is not present in blood: S. Szara, J. Axelrod and S. Perlin, Am. J. Psychiafry, 116, 162 (1958). (6) For a recent review cf. H . Sobotka, N. Barsel and J. D. Chanley, "Progress in the Chemistry of Natural Products," edited by L. Zechmeister. Springer Verlag, W e n , Vol. 14, 1957, pp. 217-243; R. A. Heacock, Chcm. Reus., 69, 181 (1959). (7) C j . Psylocybine. A. Hofmann, A. Frey, H. Ott, Th. Petrzilka and F. Troxler, E z g c r i e n f i o , 14, 397 (1958). ( S ) The indole related to mescaline, ;.e., 5,6,7-trimethoxyindole, seems to be devoid of central effects in cats [R.D. Morin, F . Benningtoil and L. C . Clark, Jr., J . Org. Chcm.. 2 2 , 331 (1957); 23, 19 (1958)l; cf.. J . Org. Chem., 24, 917 (1959). (9) E. G.Ball and T. T. Chen, J . B i d . Chcm.. 102, 691 (1933); K . iVi?sner, Biochcm. Z.,313, 48 (1912); 314, 214 (1943). (10) L. F. Fieser and M. A. Peters, THISJOURNAL, 63, 793 (1931).
011
pH 8: 287; pH5: 281
I11
0
v
pH 9: 495 332 278 z5H 7.5: 495 270 p H 5 : 385 262
VII, XEZ" 295, e 6000
1,800 2,800 11,200 2.250 10,800 1,100 16,300
[VIIa, R = HI XIV, R = Br, XIIIa, R = Br ?:A ( e ) : 303 (7600). 305, 297 (7800), 270 (7600) 6 14,000 VIII, R = H ( e ) : 297 (4600), 266 (5100)
6232
Vol. 81
SIROSENOH AND BERNHARD WITKOP I
e
d
B
me.
Fig 1 -Spectral shifts observed with ( A ) 2,4,5-trihydroxyphenethylamine( I ) and (B) 2-methoxy-4,5-dihydroxyphenethylnrnine ( Y I I ) in: ( a ) neutral ethanol (-), (b) after addition of one drop of 0.1 N YaOH (----), (c) after addition of one drop of 1 N SaOH (.-.-.) and (d) after reacidification with HC1 (. . . * s).
the methyl ethers (R = CHJ have been of diagnostic value in the determination of the amounts of a - and $-quinone forms (I< = H ) present at equilibrium. 0
droxybenzene (hydroxyhydroquinone : ,,,A 288 (E 2,8OO)),l3but not with a hydroxyindole (cf. VIII). The acid shift of the aminochrome IV to 385 and 262 mp (Fig. 1, 9-d) is reminiscent of the absorp390, E 4,200) and may possition of o-quinone (A, bly indicate an o-quinoid structure IVa present in OH
I
I
OR
0
s, .,E,,
1s , , , E , ( J
0.433
Spectrophotometric observations point to the formation of the aminochrome by the rapid sequence I + IV. Whether such a sequence is possibly involved in the test developed by Carlsson1I for the clinical assay of dopamine, is being investigated by Dr. J. R.Crout in the National Heart Institute. The two amines I and 1'11 behave quite diflerently when base is added to their ethanolic solution in contact with air. V-ith 0.1 Nsodium hydroxide Amax 295 mp of 1 (Fig. 1, ? - a ) splits into two peaks, 270 and 495 nip (Fig. 1 A-bj. By comparison, hydroxy-p-quinone absorbs a t 2U0 (E 5,000) and 480485 mp (E 2,100). For the quinone XI a band a t 460 mp (E 540) has been noted." A clear distinc-
0
x:y
il(),:Jb-
,~. ,A,
I.4
f1.t'
~..71 1
m
)
,
fi
f
0
11
('If.
~
t 460
331 288
240
€
5,400
7,200 14,500 15,100
XI
tion between the aininochrome IV and the indole quinone V I was possible after treatment with a reducing agent, NazS2O4, which after acidification showed 281 r n ~ (EtOH) in agreement with a trihyA.
Dertler, A . Carlsson, E. Roseugren ntld U. Waldeck, K m g l . Saliikupeis i L i l ~ dFdrhundliiiguu as, I 2 1 (1938) (12) Cf.H.-J. Teuber a n d G . T h a l e r , Bcv., 91, 2263 (1056).
(11)
FyJiogrufiska
IVa
acid solution. The methoxy amine undergoes oxidative cyclization and rearrangement to the hydroxyindole VI11 (Fig. l , B-d) to judge from the spectral similarity of VI11 withXIV (Fig. 2, D). It appears, therefore, that there is a noteworthy difference between 0 - and p-quinoid aminochromes. The former of type VIIa, XIIIa, adrenochrome or dopachrome undergo easy base-catalyzed isomerization to dihydroxyindoles (VIII, XIV), whereas a p-quinoid aminochrome of type IV is stable to base; its oxidation-reduction potential is too low for an internal hydrogen shift. Conclusive proof for the course and mechanism of these rearrangements came from studies with the tritium labeled amines. Table I summarizes the results. As expected there is no loss of tritium in the formation of the p-quinoid aminochrome corresponding to IV, whereas approxiniately one atom of tritium is found in the solvent containing the dihydroxymethoxyindole corresponding to VIII. It is possible to visualize trihydroxyphenethylamine as a key intermediate to which metabolic routes may lead from dopamine, from m-tyraminc and 2,5-dihydroxyphenethylaniine. l4 s n~.lsoll
.I ~ ~ ciititz ~ ,, 181, i 803 (19~0).r j LV I S I . c~ ~ i~ , 618, 117 (l'J38) (14) G Leaf and X Iieuberger. Biochcii~ J 43, I,Ub 11018)
(13) II
I C- 5alfcld,
Aitii
~
~
~
~
NEW METABOLITE OF DOPAMINE AND DERIVATIVES
Dec. 5: 1959
6233
Fig. 2.-Spectral shifts observed with ( C ) 2-methoxy-3-bromo-4,5-dihydroxyphenethylairiine(IXa), ( D ) the aniinochromo Xa and ( E ) the indole derivative XI1 in: ( a ) neutral ethanol (-), (b) after addition of one drop of 0.1 N NaOK (----), (c) after addition of one drop of 1 N NaOH and (d) after reacidification with HC1 (. * ). (.-e-.)
The preparation of crystalline aminochromes and hydroxyindoles was possible starting from the hydrogen bromide addition product to N-carbobenzyloxy - 2 - methoxy - 4,s- dihydroxyphenethylaminequinone, which could have either structure X I I a or TABLE I
which still contained one bromine atom. On the other hand, cyclization of X I I b might have led to a bromine-free compound XIIIb by an internal S N reaction. It is surprising to note that the analogous oxidative cyclization of 6-methyladrenaline to 4-methyladrenochrome should not occur.15
TRITIUM ACTIVITIES I N THE FORMATION REARRANGEMENT OF 0- AND +QUINOID AMINOCHROMES
DISTRIBUTION O F AND
activities of reactionproductsa Volatile Residual fraction fraction
--Specific Specific activities of tritiated amines
OH XIIb
Tritium content of the solvent
c
NCO); Beilskein test; evaporated to dryness under reduced pressure. As a refer6.19m; 6.69s; 6.90s; 7.10s. 215; 254; 300mp. ence, 2.117 mg. of the same dihydroxyindole-3-Ha was disA,tal. Found: C, 62.79; H, 5.90; N, 5.33. solved in methanol and left for 60 hours under nitrogen and Tritium Studies.-Tritium activities of samples were evaporated to dryness under reduced pressure. The tritium meds;ured by a Packard liquid scintillation spectrophotomactivities of both residues were measured. The former had eter. The sample solution was prepared by the following 20 c.p.m./pmole; the latter had 50 c.p.m./pmole. proci2dure: To the solution of a certain amount (approxiBETHESDA, MD. mately 100 y ) of the material in 2 ml. of methanol was added (p):
.
