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COMMUNICATIONS TO THE EDITOR
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Both the comparison of the “rate” and “all-ornone” assays and the extension of the rate assay to large values of t lead to the same conclusion, that photooxidation of a single accessible histidine residue reduces pbsphoglucomutase activity by a factor of about 1 2 Moreover, this concordance suggests that these kinetic methods, which are not theoretically limited to phosphoglucomutase or photooxidations may be useful in correlating structure with astiv.ity in other systems.
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n R 0 O R H A V E N S A T I O N A I , LADORATORY
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.60 .40 INTERCE
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WILLIAMJ. RAY,JR. UPTON,NEWYORX J O H N J. RUSCICA T m ROCKEFELLER INSTITUTE U. E. KOSKLAND, JR. YEW Y O R K C I T Y 21, .v. Y. RECEIVED J U L Y 8, 1960
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CONFIGURAnON AND OPTICAL ROTATORY DISPERSION OF ATROPISOMERIC BIARYLSI
.001
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Sir : Rotatory dispersion curves have been useful in configurational correlations of compounds amtaining asymmetric atoms.* The availability of structurally symmetrical optically active biaryls of known absolute configuration3 prompted US to secure the rotatory dispersion curves of over sixty compounds in this class. We now report the salicrit results of our investigation, which lead
\
.
.
I
2
.
..
.
--A,. 6 7 8 9 I.-:
..!
5 1011 I 2 PHOTOOXIDATION TIME IN M I N U T E S
3
4
13
40r 1
14
Fig. 2 . - k of phosphoglucomutase activity on extensive photo6xidation as measured by the “rate” assay.
kx and k y are the rate constants for oxidation of X and Y, and F is the fractional activity in the enzyme modification in which Y has been oxidized. The activity of the enzyme in which X has been oxidized is taken as zero, ;.e., undetectable by the present assay procedures. The equation gives a straight line on a semi-log plot only for small values of t in agreement with Fig. 1 but predicts a pronounced curvature a t large values of t . When photoijxidation was followed to 99.9% loss of enzyme activity such curvature was found as shown in Fig. 2. hlorcover the appropriate graphical analysis led to the evaluation of k y , kx and F as 0.64 iiiin.-l, 0.37 min.-’ and 0.078, respectively. To identify the residue, Y, rate constants for oxidation of the various susceptible residues of the enzyrnc were determined. The first-order rate constant for oxidation of the accessible histidines was found to be 0.65 min.-I. As noted previously’ part of the histidine residues of this cnzynic are relatively inaccessible to photoKxidation (k = 0.048 min.-l).* Since the oxidation constants for other susceptible residues were considerably less than 0.04 (see Ray, ct it seems quite certain that Y can be idc~itificdas an uccessible histidine residue. (1) D . E. KosNarrd, Jr.. W . J . Kay, J r . . and M . J. Erwin. Fidrrafion P i a . , 17, 1115 (1968) (2) The rate constants arc quite dependent on the detailed rcaolinn conditions which will be described in the full publication. In general the pboto6sidations were similar to those of Weil. James and Ruchert. Arch. Bistbcm. Biopkyr.. 46, 266 (1958), except for the use of mu&
higher light /ntansities. (3) W. J. Ray, J r . , I i G . Latham. Jr , hf. Katsoulis and D. E. Koshlnnd. J r . , THIS J O I J R N A I . , a, 47.43 (1960).
25 0’
0
20
(R)-ll
(S)-Vl 0
t
(R)-l
’0
(R)-lll
(S)-V
.I
15
(S)-lV
-- - - -_ _ _ -
-.-.-._
-.-.-.-
20 300
400
500
600
700
&(my).
Fig. 1. Optical rotatory dispersion curves (dioxane) of: ( K ) - I ( S = C O ) ; ( K ) - 1 1 ( S = CHOCOCOCsII,);( K ) - I 1 1 (X = CHOII); ( S ) - R ( S C(C0zCzHb)z); (S)-V ( X = 0 ) ; (S)-VI (X = direct boud between CHZgroups).
-
( 1 ) Configurationd S t u d h in tbe Siphenyl Series. I X (paper V I I I , K . Mislow and P. A. Gr-ann, J . Or#. Chrm.. ¶S, 2027 (1968))
and ”Optical Rotatory Dispersion Studies. X X X I X ” (paper X X X V I I I , C. Djerassi, W. D. Ollis and R . C. Russell,J . Chem. Soc.. in pur). (2) C . D j e r d , “Optical Rotatory Dispersion.” McCraw- Hill Book Co.. Inc.. New Ymk, 1960; see espedally Chapter 10. (3) K. Mislow. Anpcw. Chem.. TO, 683 (1958),and references cited tbcrein.
Sept. 5 , 1960
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COMMUNICATIONS TO THE EDITOR
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0 1
Fig. 3.-Optical rotatory dispersion curves (dioxane) of: (R)-VII) (Y = C(COeCpHa)2); (R)-\.III (1-= CHOH); (S)-IX ( Y = 0 ) ; (S)-X (I' = CHr); (S)-XI (I7= CHOH); (R)-XI1 ( Z = C(C02CaHs)2);(R)-XI11 in water ( Z =
+
K(CH2)aBr-).
to the conclusion that absolute conjigurutions of atropisomers m a y be successfully correlated by the rotatory dispersion method. 2,2'-Bridged4 1,l'-binaphthyls (Fig. 1) and 2,2'bridged4 biphenyls (Fig. 2) of the (R)-configuration exhibit positive Cotton effect curves while negative ones are shown by members of the (S)-series. The visible region is frequently dominated by a background rotation of opposite sign (e.g., I1 or I11 in Fig. 1). Whenever this is not the case (e.g., I in Fig. 1; XIV in Fig. 3) the monochromatic (based on [ f f ] D ) bridge rule5 is violated.6 The generalization based on rotatory dispersion is therefore more encompassing. Introduction of substituents which profoundly alter the biphenyl chromophore (as in bridged 2,,2'-dinitro-, ,2,%'diamino- and %,%'-dialkoxybiphenyls)drastically changes the rotatory dispersion pattern : thus, bridged (R)-diamino- and dinitrobiphenyls have nfgativc rotatory dispersion curves which will be discussed in our detailed paper. The multiple Cotton effect curves of the bridged ketones (R)-XIV and (S)-XIV (Fig. 3) are distinguished by (i) extraordinary amplitudes and (ii) fine-structure (reflected in the ultraviolet spectrum a t XXEP 289, 297.5, 307 and 317 mp) heretofore associated with rotatory dispersion curves of a,P-unsaturated ketones2 T o account for this observation, we postulate homoconjugation of carbonyl and benzene a-electrons7; rota(4) Bridging assures a fixed and known ( s y n - s k e w ) conformation. ( 5 ) I). D. F i t t s , h i . Siege1 and K . hlislnw, THISJ O U R N A L , 80, 480 (1U.iSi. (ti) K . llisluw and F. A. hlcGinn, i b i d . , 80, 6036 (1858).
C H j
X I V
CHj
CO~IXLJNICATIONS TO THE EDITOR
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Vol. 82
7.53), and the enantiomer, (R)-VI11 (Y = CHOH), m.p. 77-79" (fd.: C, 85.94; H, 7.48) by LiAlH4 reduction of (S)-XIV respectively (R)-XIV; (S)-X (Y = CHz), m.p. 63-64' (fd.: C, 92.05; H, 8.38), by modified Clemmensen reduction of (S)-XIV; (R)-XI1 (2 = C(COOEt)2), m.p. 165-167' (fd.: C, 61.75; H, 5.07; C1, 17.29), from (+)-6,6'dichloro-2,2'-bis-(bromomethyl)-biphenyland malonic ester.
Using ionic catalysts, we have prepared two new types of crystalline dimethylketene polymers of regular chemical structure. Dimethylketene in toluene solution was polymerized a t -60' in the presence of aluminum tribromide (moles monomer/ moles catalyst approximately 1500); the fraction, which was not extractable with boiling toluene, had an intrinsic viscosity of 0.7 in nitrobenzene a t 135' ; m.p. 250-255' (determined with a polarizing microscope). (9) Support by t h e Alfred P. Sloan Foundation is gratefully acknowledged. The high crystallinity (see Fig. 1) of this fraction (10) Trubek Fellow. 1958-1959; N S F Cooperative Fellow, lY3Q- (polymer I) indicates that i t is made up of micro1960. molecules having a regular structure. The strong (11) Trubek Fellow, 1937-1958. absorption in the infrared spectrum (Fig. 2 ) near (12) Supported by t h e Sational Cancer Institute (by grant ,'\lo. CRTY-3OGl) and the National Science Foundation. Rotatory disper5.9 I* indicates the presence of carbonyl groups, sion measurements were performed by l f r s . T. Nakano and Rlrs. R u t h a conclusion which is confirmed by the ultraviolet Record with an automatically recording Rudolph spectropolarimeter. spectrum The two bands around 7.25 p are in KCRTMI SLOW^ accord with the presence of one type only of gem L)EPARTMENT O F CHEMISTRY M, A. LV. GLASS SEW YORKUNIVERSITY ROBERT E. O'BRIEN'O methyl groups. SEW YORK5 3 , N.Y. PHILIPRUT KIN^^ DAVIDH. STEINBERG
OF CHEMISTRY DEPARTMEXT STASFORD UNIVERSITY C.4RL STANFORD, CALIF. RECEIVED JULY 18, 1960
I)JERASSI"
CRYSTALLINE POLYMERS O F DIMETHYLKETENE
Sir: I t is known that dimethylketene dimerizes readily Higher polyto tetramethyl-1,3-~yclobutanedione.~ mers were obtained by Staudinge? using aliphatic or aromatic amines as catalysts. These amorphous products can be considered as derived from the irregular copolymerization of the two monomeric
I
CHI
I, -c-o-
(a)
(8)
units formed, respectively, by the opening of the ethylenic or of the carbonyl double bond.
L 20 25 28. Fig. 1.-X-Ray Geiger registration (CUKCY) of the two crystalline poly-dimethylketenes: -polymer I , --------polymer 11. 3
10
15
(1) H. Staudinger, H. Schneider, P. Schotz and P. hl. Strong; Helv. Chim. A d a . 6, 291 (1923). (2) H. Staudinger, i b i d . , 8 , 306 ( 1 9 2 3 .
01
I
3
5
7
b
'
,
11
,
,r
13
Fig. 2.-Infrared spectra of the two crystalline polydirnethylketenes, mulls in Xujol and C4Cl8: -polymer I, --------- polymer 11.
From the chemical properties of polymer I we conclude that i t consists of macromolecules formed by the regular head-to-tail enchainment of monomeric units of type (a). In fact, polymer I behaves chemically like a p-diketone; treatment of I suspended in tetrahydrofuran with excess ethyl alcohol and a small quantity of sodium ethoxide, for a long time (100 hours) a t 200-26O0, yielded ethyl isobutyrate and di-isopropyl ketone in addition to the unchanged polymer. The structure assigned to polymer 1 has been confirmed by the results of reduction of the carbonyl groups with LiAIHt. Treatment of I suspended i n tetrahydrofuran with LiAlH4 gave a white, airiorphous polymer (90% yield) which was insoluble in ether and acetone, but soluble in acetic acid and ethyl alcohol. The infrarcd spectrum shows that only traces of carbonyl groups remain, whereas there is strong absorption a t 3.02 p which is attributable to associated hydroxyl groups. This reduction product, therefore, is an atactic polymer of polydimethylvinyl alcohol Polymerization of dimethylketene under the conditions previously mentioned with triethylaluminum as the catalyst, gave a polymerizate, 70yo of which can be extracted with boiling benzene, but not with boiling acetone. This fraction (polymer 11) has an intrinsic viscosity of 0.4 (in tetralin a t 135') and a regular structure as indicated by its high crystallinity (see Fig. 1). The two bands a t 5.71 and 5.75, (only the 5.75, band occurs in solution) indicate the presence of ester groups. That only traces of carbonyl groups are present is demonstrated by the weak absorption bands a t 295 mp in the ultraviolet.
