Optical rotatory dispersion of sugars

Optical rotatory dispersion of sugars

o3?Jzxz~ Rs3TATORY DzsEBex OF IV. CONFIGURATION AND CONFORMATION OF IRVING LISTOWSKY**, GAD Avmmt, Department of Brochemlsrry, New York 10461 ...

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o3?Jzxz~

Rs3TATORY

DzsEBex

OF

IV. CONFIGURATION AND CONFORMATION OF IRVING

LISTOWSKY**,

GAD

Avmmt,

Department of Brochemlsrry, New York 10461 (U S A 1

Albert

AND

sxeARs*

LJRONIC

ACIDS

AND

ACEJYAMIDO

SUGARS

SASHA ENGLARD

Emstem

ColIege

of Medwmne,

Yeshrva

Uncversrty,

Bronx,

(Received May 23rd, 1968)

The optical rotatory dlsperslon propemes of uromc acids and acetarmdo sugars have been mvestigated For both categones of sugars, two optically active transltxons have been lmphcated as the foremost factors determimng the shapes of the rotatory &sperslon curves m the spectral region below 230 nm By a study of difference curves, the rotatory propeties associated with the mdivldual anude and carboxyl chromophores were isolated The curves for the uronrc acids were characterized by positive Cotton-effect peaks near 220 nm and negative Cotton effects shown below 190 nm These features were ascrlbed to the mfiuence of the equatorial carboxyl group on the pyranold rmg The acetarmdo sugars were found to extiblt curves havmg a Cotton-effect mimmum near 220 nm and a Cotton-effect peak at 200 nm The present data have also been related to the results obtamed previously for sugars lackmg acetarmdo or carboxyl substituents, and these conform with the estabhshed views relatmg far-ultraviolet rotations to the configuratlon and conformatlon of the cychc forms of sugars INTRODUCTION

Optical rotatory dlsperslon (0 r d ) studies have recently been repol’ted for a large number of cychc sugars m solufion’ -4, and empmcal relatlonshlps between the shapes of the o r.d curves and known features of conf?guiatlon and conformation of these sugars have been derwed’. Rotational properties in the spectral regon below 210 nm were shown to be particularly slgxuficant, smce many of the curves were no longer plam m this spectral reDon, and, m some Instances, abrupt changes in the &ecfion of rotation were observed These infiections resulted from the combmed *Thismvatlgatlon was supported b> Grants HE-l 1511 and GM-04428, from the NatIonal Institutes of Health,and by Grant U-1901 from the Health Research Councd of New York For previous paper m tEus series, see ref 1 This work was presented, in part, at the symposfu on “Newer Aspects of 153rcI Natfonaf Meet&g of the American Chem
Res L 8 (1968) 205-213

I. LISTOWSKY, G AVIGAD, S ENGLARD

206

mfiuence of the part& rotatory contributions of the mdlvldual asymmetric centers m the spectral region approachmg the optically active absorption bands, rather than from extrema of Cotton effects Circular dlchrolsm (c d ) spectra mdrcateds that optically active transItions for simple sugars are located at wavelengths well below 2OOnm Such sugar denvatwes as lactones6, C-mtro alcohols’**, sugar mtratesg-‘l, and sugar-molybdate complexes l2 exhibit Cotton effects m the spectral reBons of then respective absorption bands, and the o r-d. data were related to structural features of these molecules Chondroltm sulfates A, B, and C etibit Cotton-effect peaks nearI 220 nm and the U(L) conformation of the L-ldosyluromc moiety m chondroltm sulfate B was proposed on the basxs of the o r.d results Dlsulfated dlsacchades obtamed from chondroltm sulfate by dIgestIon with chondroitmase have also been studied by o r d methods 14. 0 r d and cd measurements have recently been applied to a study of the conformation of ohgosacchmdes (such as blood-group substances’4 and rmlk ohgosacchandes”) that contam acetanudo sugar residues The present study is a report on the o r d. propemes of some representative acetanudo sugars and uromc acids. The results have been compared to the data obtamed prevlous!y with simple sugars’ l3l 4, and attempts have been made to Isolate and evaluate the rotatory contribution associated with the amide and carboxylate chromophores RJZXJLTSANDDISCUSSION In our previous studies, the suggestion was made that the electronic transitions associated with the ring-oxygen atom of the furanold or pyranold forms of sugars govern the shapes of the o r d. curves m the spectral region3 between 210 and 185 nm. General rules were therefore proposed that related the directIon of rotation m the far-ultravloIet to the spatial dlsposltlon of the rmg substltuents relative to the rmgoxygen atom3 The mtroductlon of acetamdo or carboxyl substltuents on the rmg should Induce Cotton effects that are directly related to the posukon of these chromophores, and, as a tist approxlmatlon, may be stud& apart from the remamder of the molecule In addition, the effect of an acetanudo or carboxyl substltuent on the optically active absorption bands of the rmg-oxygen atom may be evaluated Acetamzdo sugars - 0 r.d curves for some sugars having equatonal acetamldo substituents* at C-2 are shown m Fig 1X The Cotton effect curves m the 230-190 nm spectral regon e&blt small troughs or nunima near 220 nm and distinct peaks near 200 nm The molar rotations of the or-D-glycosidic forms are more positive than those of the J-D forms, mdlcatmg that the rotations are highly dependent on the con& guratxon at C-l. C d spectra for some acetarmdo sugars are shown m Fig. 1B N-Acetyl-D-mannosamme (2-acetarmdo-2-deoxy-D-mannose) (having an axial acetanudo substituent on C-2) has a positive elhpticlty band near 210 nm, as opposed to the negative c d bands for N-acetyl-D-glucosamme (2-acetamido-2-deoxy-D*To smphfy the dmxsston, the sugars of the D-senes are cons.deredto be 111the cl conformation. Carbohyd

Res,

8 (1968) 205-213

I. LISTOWSKY,G_ AVIGAD,S. ENGLARJIJ

212

peaks near 205 run wer-p observed for the (methyl a-D-mannopyranosld)uronates 2900) and (methy cx-D-glucopyranosld)uronates ([MJtos 44OO), and near (P&35 215 nm for (methyl a-D-ga!actopyranosid)monates ([Ml2 15 3760) The rotational values at the peaks for the correspondmg free acids are [Mlz15 2950, [MJz13 4400, and j&4Jzzs 3800, respectiveIy (see Frg 3) The difference curve obtamed by subtractmg the value for the D-glucoeduronate from that for the D-galactoslduronate IS srrmlar to that

Fjg 5 OptIcal rotatory dlsperslon dflerence-curves for the uroruc ands pyranosiduromc acid mmus methyl a-D-glucopyranos~duromc acid, - - pyranosxduromc acid mmus methyl a-D-ghxopyranoslduromc acid

methyl a-n-galactomethyl a-D-manno-

obtamed with the corresponding free acids, and shows the characterlstrc inffectlon and change m dlrectlon from posltlve to negative near 220 nm AIso, the curve for the D-mannopyranoaduronate mmus the D-glucopyranoslduronate exIublts the same change In dIrection of rotation from negative to posltlve near 200 nm as that obtamed with the correspondmg free acids A “blue shift ” IS observed m the Cotton-effect peak for the sodmm salt of poly(a-D-galactonduronrc acrd) (pH 9 0) as compared to the free acid (pH 2 8) The rotational magmtudes at the peaks are comparable, however, mdrcatmg that the conformation of the macromolecule 1s Independent of the state of ionization of the carboxyl groups EXPERIMENTAL Matends

-

Most of the sugar denvahves

CorbohydRes ,8 (1968) 205-213

employed for thus study were

(IPTICAL

ROTATORY

DISPERSION

OF SUGARS

213

IV

obtamed from commercral sources, or were syntheszed by using commerctally available startmg-materials Each compound was checked for opttcal punty by measurement of the specific rotation at 589 nm, and the values agreed with those reported m the hterature We are grateful to Dr R Ledeen for samples of methyl 2-acetamtdo-2-deoxy-or- and -/?-D-galactopyranostde, to Drs E Kabat and K. Lloyd for methyl 2-acetarmdo-2-deoxy-sr- and -/?-D-glucopyranoslde, to Dr T E Time11 for propyl fi-D-glucopyranosiduronate. to Dr E E Drckey for the (methyl a-D-glucopyranosrd)uronates, to Dr 0 Samuelson for the (methyl cc-D-mannopyranosxd)uronates, and to Dr C A Marsh for the (methyl a-D-galactopyranosid)uronates All soluttons were prepared m dIstilled water, and solutions of the free uromc actds were obtained by treatment of then salts wrth Dowex-SO(H+) ion-exchange resm The pHs of the uromc acid solutrons were near 3, and their salts were studred at pH 7-9 0 r d data for the mutarotatmg sugars were recorded after constant values of the specmc rotation had been attamed Spectropolarlmetric studies - The o r d measurements were made wrth a Cary Model 60 spectropolarrmeter. Cylmdr~cal, quartz cells havmg path lengths of 0 05,O 2, 1 0, and 10 mm were used Absorptton values of 2 0 were never exceeded, and 1.0 per cent sugar soluttons were employed for the vlslble and near-ultravrolet rotahocs, approprrate drlutlons were prepared for the far-ultravtolet o r d measurements The slit-wtdth of the polarrmeter was programmed for half band-wrdths of less than 1 5 nm through the enttre spectral range For increased intensity of hght and for precrsron of the measurements m the far-ultravrolet, a Xenon arc, XBO-450,/4 lamp was used C d measurements were made by use of the c d accessory for the Cary Model 60 spectropolarrmeter. The experimental condrtrons were solar to those employed for the spectropolarrmetnc measurements REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

S ENGLARD, G AVIGAD, AND I LWOWSKY, Carbohyd Res ,2 (1966) 380 N. PACE, C TANFORD, AND E A DAVIDSON, J Amer Chem Sot, 86 (1964) 3160 I LISTOWSKY, G AVIGAD, AND S ENGWRD, J Amer Chem Sot, 87 (1965) 1765 I LISTOWSKY, S ENGLARD, AND G AWGAD, Carbohyd Res ,2 (1966) 261 I. LlSTOWsKY AND S ENCLARD. Bzochem Blophys Res Commun , 30 (1968) 329 T OKUDA, S NARIGAYA, AND A KIYOMOTO, Chem Pharm Bull (Tokyo) 12 (1964) 504 C SATOH AND A KIYOMOTO, Carbohyd Res ,3 (1966) 248 C SATOH, A KIYOSIOTO, AND T OKUDA, Chem Pharm Bull (Tokyo), 12 (1964) 518 Y TSUZUKI, K TANABE, AND K OKAMOTO, BUN Chem Sot Japan, 38 (1965) 274 Y TSUZUKI, K TANABE, AND K OKAMOTO, Bull Chem Sot Japan, 39 (1966) 761 Y TSUZUKI, K TANABE, K OKAMOTO, AND N YAMADA, B&N Chem Sot Japan, 39 (1966) 1391,2269 L VELLUZ AND M LEGRAND, Compt. Rend, 263 (1966) 1429 E A DAVIDSON, Brochlm Blophys Acfa, 101 (1965) 121 S SUZUKI, H SAITO, T YAMAGATA, K ANNO, N SENO, Y KAWAI, AND T FIJR-A~HI, J BIO~ Chem ,243 (1968) 1543 S BEYCHOK AND E. A KABAT, Blochemzstry, 4 (1965) 2565 K 0 LLOYD, S BEYCHOK, AND E A KABAT, Blocbemrstry, 6 (1967) 1448 J S HAMM AND J R PLX~-~, J. Chem Phys, 20 (1952) 335 J_ Amer Chem Sot ,67 (1945) 673 I I RUSOFF, J R PUTT, H B I&EVENS, AND G 0 Bw, Carbohyd

Res , 8 (1968) 205-213