3538
COMMUNICATIONS TO THE EDITOR
acid-catalyzed conditions which have proved effective with 17~z-hydroxy-20-ketosteroids,31but only unreacted starting material was recovered. (31) Cf.Huang-Minlon, E. Wilson, PI'. L. Wendler and M. Tishler, THIS J O U R N A L , 74, 5394 (1952); R. B. Turner, ibid., 76, 3489 (1953).
Vol. 7 8
Acknowledgment.--We should like to acknowledge the benefit of a stimulating discussion wit. Prof. Gilbert Stork of Columbia University. DETROIT,MICHIGAN
COMMUNICATIONS T O T H E EDITOR THE RESOLUTION O F 0-ETHYL ETHYLPHOSPHONOTHIOLIC ACID
Sir:
presence of a reactive group directly attached to phosphorus in a resolved compound of this type provides one with a convenient tool applicable t o a study of the reactions and stereochemistry of the asymmetric phosphorus atom. Detailed reports on the resolution, reactions and stereochemistry of this and similar compounds will be published a t a later date.
We wish to record the successful resolution of 0-ethyl ethylphosphonothiolic acid (C?Hs(C*HsO)P(O)SH).l The compound was resolved by fractional recrystallization of its quinine salt (I) from acetone-ether. The more insoluble diastereoisoRESEARCH DIVISION meric salt (Ia) crystallized as a monohydrate : CHEMICAL OF RESEARCH HERBERT S.AARON prisms, m.p. 151-153O (with loss of its water of DIRECTORATE CHEMICAL WARFARE LABORATORIES JACOB I. MILLER hydration), [ a I g 6 D -96.6 + 0.S' (sobs -1.990 + ARMY CHEMICAL CENTER, MD. 0.015O, acetone, 2-dcm., c = 1.130), equiv. wt., RECEIVED MAY21, 1956 492 (calcd. 497 for the monohydrate). IVhen vacuum dried over phosphorus pentoxide for three ELECTROPHORETIC DEMONSTRATION OF THE hours a t looo,I a gave rise to anhydrous product. ISOMERIZATION O F BOVINE PLASMA ALBUMIN m.p. 15S-1GOo, [ c u ] ~ ~-9'7.6 D =k 0.6' (aohs -1.0'70 AT LOW pH 0.007', acetone, 1-dcm., c = 1.096), equiv. wt., Sir: 469 (calcd. 479). Recently much interest has been exhibited in a The acid was separated from I a as its sodium pronounced conformational change which takes salt in an essentially aqueous solution by treating place in bovine plasma albumin a t pH values acid I a in methanol with an equivalent amount of to the isoelectric point. I t was first suggested by aqueous base. T h a t the phosphorus atom main- Tanford' that expansion of the protein molecule tains its tetrahedral configuration in the anion is results upon titration with acid. Gutfreund and demonstrated by the optical activity of the product Sturtevant' demonstrated a slow thermal effect recovered from the sodium salt. The acid was re- upon adding acid to this protein. Yang and Foscovered by the addition of an equivalent amount of ter3 demonstrated a parallel and reversible endilute hydrochloric acid to the sodium salt solution hancement of the optical rotation and intrinsic and extraction of the product from the resulting viscosity acid to p H 4, and suggested that there solution with ether. The acid was characterized as exists an all-or-none equilibrium between two its dicyclohexylamine salt: m.p. 139- 1C10.5~ forms of the protein molecule. Tanford4 has re[a]?'D -7.11 zk 0.23' ( a n b e -0.153 =I= 0.003', cently shown evidence for an intermediate which methanol, 1-dcm., c = 2.150), found: C, 37.38; he terms the "expandable" form. H , 10.00 (calcd. for C16Hd403NP: C, 5'7.2s; H , \Ve have recently been successful in attaining 10.22). excellent resolution of two boundaries in the elecAfter the removal of a mixed middle crop of I, trophoretic patterns of this protein over the FH the more soluble diastereoisomeric salt (Ib) crys- range 4.6 to 3.5. Heterogeneity of plasma altallized as soft anhydrous needles: m.p. 1GG- 16S0, bumins in this pH range has been reported prc[CU]?~D -S1.'7 + 0.6' ( m o b s -1.613 f 0.012, ace- ~ i o u s l y . ~ -However, ~ we can now demonstrate tone, 2-dcm., c = 0.9868);equiv. wt., 475 (calcd. that this heterogeneity is due in the main to a fiH 479). The dicyclohexylamine salt of this enantio- dependent transition of the normal form of the promorph of the acid gave m.p. 158-160°, ( c ~ ) ' ~ D tein into a faster migrating form. presumably of +6.85 0.23' (sobs 0.221 + 0.008", methanol, higher positive charge. Results summarized in 1-dcm., c = 3.230), found: C, 57.30, H 10.02, mixed (1) C. Tanfurd, Proc. I o z , a A c a d . S c i . , 69, 200 (1932). melting point with the enantiomorphic dicyclo(2) H . Gutfreund and J . Sturtevant, THIS J O U R K A I . , 76, 5k17 hexylamine salt, above. 163- 165'. Racemic 0- (1933). ( 3 ) J . T. Y a n g and J . Ii. Foster, i b i d . , 76, I388 (19.51); 77, 2371, ethyl ethylphosphonothiolic acid forms a dicyclo3805 ( 1 9 ~ 5 ) . hexylamine salt, m.p. 166- 16s'. (1) C. Tanfurd, J . Buzzeil, D. Rands a n d S . Snanwii, i b i i i , 77, 1,421 This communication represents the first reported (195.5). resolution of a phosphorus acid, the optical ac( 5 ) J . Luetscher, ibid., 61, 2888 (1939). hriii , (A) D. Sharp, G. Cooper, J. Erickson and H . h'eurath, J . Bioi ti\ity of which is due solely to the presence of an 144, 139 (19L?). I n this paper i t was also shown that hetemjieneity asymmetric phosphorus atom. AIoreover, the c1is:rpl)ears b e l o w pH 3 . 5 , in uccord with oiir (Iwn r e i u l t . .
*
+
( 1 ) T h e preparation o f alkylph~,sphonath,~,lic a c ~ d . \\,I1 be d e w r l b p d in a forthcoming paper h > I* XT' Hufim,inn a n d r i ! iTI) aggregated inateri.il
(1) Supported in p a r t by a research grant from t h e National Institutes of Arthritis and Metabolic Diseases of t h e National Institutes of Health, Public Health Service; anti in part h y the Dnmrm R u n y o n Fund a n d t h e American Cancer Society
