VOL. 32 (1959)
`
`PRELIMINARY NOTES
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`295
`
`Synthesis and biological activities of iododeoxyuridine,
`an analog of thymidine
`
`Iodinated derivatives of uracil and of uracil-containing compounds have been
`synthesized previously and some of their biological activities investigated1 • 2• Whereas
`5-iodouracil has been shown to be an effective inhibitor of microbial growth2 and to be
`readily incorporated into the deoxyribonucleic acids of several microbial species3• 4,
`5-iodouridine and 5-iodoorotic acid were biologically inert in the systems which were
`investigated1 . These studies have been extended by the present report to the corre(cid:173)
`sponding iodinated deoxyribonucleoside.
`5-Iododeoxyuridine was synthesized by a modification of the method described
`previously for the synthesis of 5-iodouridine1. Uracildeoxyriboside (400 mg), iodine
`(400 mg), chloroform (z ml) and HN0 3 (1 N, 4 ml) were refl.uxed gently for z h
`during which time white needle crystals of iododeoxyuridine formed. The reaction
`mixture was decanted into a sintered-glass funnel and the product was washed with
`ether until the unreacted iodine had been extracted. After recrystallization from hot
`water the yield was 350 mg or 56 % of theory.
`Analysis. Found: C, 30-46; H, z.gs; N, 8.o5; I, 35.45; Calc. for C9H 110 5N 2I:
`C, 30.51; H, 3.rr; N, 7.91; I, 35.88. Decomposition occurred at 160° and fumes of
`iodine appeared at 180°.
`The u.v.-absorption characteristics of several iodinated pyrimidines and their
`parent compounds are shown in Table I.
`
`ULTRAVIOLET ABSORPTION MAXIMA AND MINIMA OF SOME DERIVATIVES OF URACIL AND IODOURACIL
`
`TABLE I
`
`NaOH (o.oi N)
`
`HCl(O.OI N)
`
`Compound
`
`lodouracil
`Uracil
`Iodouridine
`Uridine
`Iododeoxyuridine
`Deoxyuridine
`
`max.
`m1•
`
`304
`284
`278
`262
`278
`262
`
`min.
`ml'
`
`256
`241
`253
`236
`2 53
`242
`
`max.
`mf.'
`
`283
`259
`289
`262
`288
`262
`
`min.
`ml'
`
`245
`227
`249
`230
`248
`231
`
`The u.v.-absorption spectrum of the synthetic iododeoxyuridine agrees with that
`of material isolated from microbial DNA by ZAMENHOF et al. 3 and by DuNN AND
`SMITH4• FRIEDKIN AND ROBERTS5 presented evidence for the formation of iododeoxy(cid:173)
`uridine by a mammalian enzyme, but no characterisation was given. The insertion of
`the iodine atom into each pyrimidine derivative results in a bathochromic effect;
`however, in alkaline solution the u.v. maximum for iodouracil shifts to a l(!mger wave(cid:173)
`length, whereas the corresponding riboside and deoxyriboside shift to a lower wave(cid:173)
`length. The non-iodinated nucleosides in alkali show no shift in their absorption
`maxima.
`The iodinated derivatives are readily separated from the parent compound and
`
`Abbreviations: DNA, deoxyribonucleic acid; RNA, ribonucleic acid,
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`296
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`PRELI:\IIKARY NOTES
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`voL. 32 (rgsgl
`
`from each other by paper chromatography employing the ethyl acetate-phosphate
`buffer system6 (Table II).
`Insertion of the iodine atom into the molecule results in a marked increase in the
`mobility of each of the pyrimidine derivatives; however, there is no alteration in the
`order of migration.
`Iododeoxyuridine may also be synthesized by a modification of the method of
`joHNSON AND joHNS7 for iodouracil. Deoxyuridine (228 mg), iodine (250 mg), and
`NaOH (3 N, 2 ml) were heated on a steam bath for 15 min; after dilution with water
`(So ml) the solution was passed through a Dowex-r-formate column. After washing
`the column with NaOH (o.or N) until no iodide appeared in the effluent, as indicated
`by reaction with AgN0 3, elution was continued with formic acid (o.r N). Immediately
`after the elution of unreacted deoxyuridine, iododeoxyliridine appeared.
`
`TABLE II
`
`Rp VALUES OF SOME DERIVATIVES OF URACIL AND IODOURACIL
`
`Solvent: Ethyl acetate saturated with phosphate buffer (0.05 M, pH 6.o).
`
`Compound
`
`RF
`
`Iodouracil
`Uracil
`Iododeoxyuridine
`Deoxyuridine
`Iodouridine
`Uridine
`
`0.75
`o.2I
`o.67
`o.I2
`0.44
`o.o6
`
`In contrast to iodouridine, iododeoxyuridine is almost as effective as iodouracil
`as an inhibitor of the growth of Streptococcus faecalis (ATCC 8043), when grown in
`media supplemented with thymine, thymidine or pteroylglutamic acid. With mouse
`Ehrlich ascites carcinoma cells in vitro, iododeoxyuridine but not iodouracil or
`iodouridine reversibly inhibited the utilization of 14C-labeled thymidine for the bio(cid:173)
`synthesis of DNA-thymine. Iododeoxyuridine inhibited markedly the utilization of
`[14C]orotic acid or [14C]formate for the biosynthesis of DNA-thymine, but not of
`[14C]orotic acid for the biosynthesis of DNA-cytosine or RNA pyrimidines. Hence the
`mechanism of action of iododeoxyuridine would appear to be an inhibition of the
`utilization of a thymine-containing precursor of DNA-thymine. Details of the bio(cid:173)
`logical studies will appear elsewhere.
`This investigation was supported by a grant (CY -3076) from the National Institutes
`of Health, U.S. Public Health Service.
`
`Department of Pharmacology Yale University,
`School of Medicine, New Haven, Conn. (U.S.A.)
`
`WILLIAM H. PRUSOFF
`
`1 W. H. PRUSOFF, W. L. HOLMES AND A. D. WELCH, Cancer Research, 13 {I953) 22!.
`2 G. H. HITCHINGS, E. A. FALCO AND M. B. SHERWOOD, Science, 102 (I945) 251.
`3 S. ZAMENHOF, B. REIN!tR, R. DEGIOVANNI AND K. RicH,]. Biol. Chem., 2I9 (I956) I65.
`4 D. B. DuNN AND J.D. SMITH, Biochem. ]., 67 (I957) 494; Nature, I74 (I954) 305.
`5 M. FRIEDKIN AND D. ROBERTS, j. Biol. Chem., 207 {I954) 257.
`6 W. H. PRUSOFF, j. Biol. Chem., 215 (I955) Bog.
`7 T. B. JoHNSON AND C. 0. JoHNs, f. Bioi. Chern., I (1905-o6) 305.
`Received November 2oth, rg58
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