[CONTRIBUTION F R O M
THE
GEORGEM. MOFFETTRESEARCH LABORATORIES, COKN
PRODUCTS K E P X N I N G C O . ]
The Synthesis of Aryl-D-glucopyranosiduronicAcids1 BY G.N. BOLLENBACK, JOHN W. LONG,D. G. BENJAMIN AND J. A. LINDQUIST RECEIVEDDECEMBER 29, 1954 Several methyl (aryl tri-o-acetyl-P-D-glucopyranosid)-uronateshave been prepared by the fusion of methyl tetra- 0acetyl-0-D-glucopyranuronate with phenols in the presence of acid catalysts. Methyl (phenyl tri-0-acetyl-B-D-glucopyranosid)-uronate has been prepared by fusion and by several other methods. Both phenyl or-D-glucopyranosiduronic acid and the corresponding acetylated methyl ester have been prepared and their identities established. Various aspects of the reactions of glucuronic acid and glucuronolactone with alcohols in the presence of acids and bases are reported. The anomeric aretates of 2-hydroxyethyl glucuronate have been prepared and identified.
Among the numerous derivatives of glucuronic acid the aryl glucosiduronic acids are particularly important since many of them are of biological origin.2 The chemical synthesis of such compounds has been studied by Tsou and Seligman3s4who have prepared phenyl3 and 2-naphthyl4 @-D-glucopyranosiduronic acids by catalytic oxidation of the corresponding glucosides using the procedure of Marsh.5 The same authors reported the synthesis of phenylS and 2-naphthyl4 P-D-glucofuranosidurono-y-lactones (as their diacetates) using the well known fusion technique of Helferich and Schmitz-Hillebrecht6 We wish, in passing, to note that the synthesis of the latter of these compounds in these laboratories' by an identical but independent procedure confirms the results of Tsou and Seligman in this regard. The commercial availability of glucuronolactone8 makes this substance particularly attractive as a starting point for the synthesis of aryl glucosiduronic acids and the present research was aimed a t exploring this subject. The following methods, for the most part general for the preparation of aryl glucosides, were studied as a means of making methyl (phenyl tri-0-acetvl-P-D-glucopyranosid) uronate. (1) Treatment of phenol with methyl (tri-0acetyl-a-D-glucopyranosyl bromide) -wonate in the presence of silver carbonateg (31y0yield). ( 2 ) Treatment of potassium phenolate with methyl (tri-0-acetyl- a-D-glucopyranosvl bromide) uronate in ethanol1° (75% yield). ( 3 ) Fusing phenol with methyl tetra-0-acetyl-@D-glucopyranuronate in the presence of either ptoluenesulfonic acid or zinc chloride'-'' (55 and :joy0yields). (4) Fusing phenol with methyl tetra-0-acetyl-aD-glucopyranuronate in the presence of zinc chloridell (5% yield). ( 5 ) Treatment of phenol with methyl (tri-0(1) Part of this work was presented before the Division of Sugar Chemistry a t the 124th National Meeting of the American Chemical Society, Chicago, Ill., September, 1933. (2) H.G. Bray, Adoanccs i n Carbohrdralc Chcm., 3 , 251 (1953). (3) K.-C. Tsou and .4. M. Seligman, THISJOURNAL,7 6 , 1042 (1953). (4) K.-C. Tsou and A. M. Seligman, ibid.. T4, 5605 (1952). (5) C. A. Marsh, J . Chcm. Soc., 1578 (1952). (6) B. Helferich and E. Schmitz-Hillebrecht. Bcr., 6 6 , 378 (1933). (7) G. N.Bollenback and Elizabeth M. Osman, unpublished work. ( 8 ) Marketed as Glucurone by Corn Products Refining Company. New York, N. Y. (9) N.M. Carter, Bcr., 83, 586 (1930). (10) A. Michael, A m . Chcm. J . , 1 , 306 (1879). (11) Edna M. Montgomery, N. K. Richtmyer and C. S. Hudson, THIS JOURNAL, 84, 690 (1942).
acetyl-a-D-glucopyranosyl bromide i-uronate i n t h e presence of quinolineL2(23y0yield), The yield figures are for the pure d-anomer. Procedure ( 3 ) (p-toluenesulfonic acid) was found preferable from both the standpoint of yield and convenience. This procedure was applied successfully to the preparation of numerous other esterified aryl @-D-g~ucopyranosiduronicacids. Under the conditions used the reaction was not entirely general. For instance, crystalline esterified ir)-D-glUcopyranosiduronic acids could not be isolated from fusions with o-nitrophenol, a-chlorophenol or salicylaldehyde. The crystalline esterified conjugates of o-nitrophenol and o-chlorophenol were eventually obtained by using the procedure of Mannich'" as modified by Glaser and W ~ 1 w e k . l ~\Vith hydroquinone and resorcinol, which might be expected to give d i g l y c ~ s i d e s , sirups ~ ~ * ' ~were obtained. The melting points of some of the esterified conjugates prepared chemically (notably where aryl is phenyl, o-tolyl and m-tolyl) are some 10 degrees higher than those prepared from biological uronic acids. The elemental analyses of the chemically prepared compounds indicate that no radical change has occurred during synthesis. The possibility is that the compounds herein reported represent more stable dimorphs. This is emphasized because of the agreement of rotations and also because of experience with initial preparations of the esterified phenyl @-D-ghcopyranosiduronic acid. The first preparations of the compound had melting points in the 117-118' range. Repeated recrystallizations from ethanol failed to increase the constant. I t was only after substitution of isopropyl alcohol that the higher melting point (126.5127.5') was established. The higher melting point is retained on recrystallization from either ethyl or isopropyl alcohol. Most of the methyl (aryl tri-@acetyl-ir)-D-glucopyranosid)-uronates reported here have been prepared previously from the biologically available uronic acids.I7 -4 comparison of physical constants may be made in Table I. New compounds have been obtained from catechol, naphthols and methyl gentisate. During the preparation of this manuscript biosynthesis of 1- and 2-naphthyl @-D-glUCOpyranosiduronic acids was reported. l 9 A comparison of physical constants recorded by the English (12) E. Fischer and L. v. Mechel, Bcr., 49, 2813 (1916). (13) C. Mannich, A n n . , 394, 225 (1912). (14) E. Glaser and W. Wulwek, Biochcm. Z., 146, 514 (1924). (15) B. Helferich and W. Reischel, A n n . , 533, 278 (1938). (16) A. Robertson and R. B. Waters, J . Chcm. Soc., 2729 (1930). (17) I. A. Kamil, J . N. Smith and R. T. Williams, Biochcm. J . , 60,
235 (1951).
June 20, 1955
SYNTHESIS OF ARYL-D-GLUCOPYRANOSIDURONIC ACIDS
331 1
TABLE I COMPARISON OF PHYSICAL CONSTANTS OF METHYL (ARYLTRI-~-ACETYL-~-D-GLUCOPYRANOSID)-URONATES PREPARED CHEMICALLY WITH THOSE OBTAINED FROM BIOLOGICALLY PREPARED URONICACIDS Aglycone
M.P., OC.
Chem.
Bio
[ C ~ ] * ~ -(c~ D 1,
Chem.
CHCla) Bio.
-Anal. Calcd. C
(chem. syn.), %Obsd. C
H
H
Phenyl
126.5-127.5
11618
-35.6
-33.0
55.61
5.36
55.65 55.40
3.44 5.34
o-Chlorophenyl p-Chlorophenyl o-Bromophenyl p-Bromophenyl o-Iodophenyl o-Tolyl m-Tolyl P-Tolyl o-Hydroxyp henyl 1-Naphthy 1 2-Naphthyl Methyl gentisate o-Nitrophenyl
151-1 52 152-154 137-140 162-163.5 160-162 138-140 113-115 137-138 136-137 126-127; 157-159 188-190 134-136 175-176
151-15217 151-152" 141-14317 157-1 5817 161-162l' 131l' 93-94" 1401'
-64.8 -32.2 -64.1 -29.5 -63.6 -40.6 -32.8 -31.3 -33.4 -75.5 -29.4 -26.3 f19.0
-65.0 -32.9 -64.6 -28.0 -63.3 -46.0 -25.6 -36.0
... ...
..
...
... ... ...
..
.. ..
...
..
...
.. ..
5.66 5.66
56.38 56.87
5.45 5.57
..
...
..
....
56.60 56.60 ... 53.52 60.00 60.00 52.07
5.16 5.22 5.22 4.96
53.41 60.11 59.99 52.29
4.92 5.12 5.11 4.88
+18.5
...
..
...
..
...... 160'' 127- 128'*
...... 172M
.... -79.0 -35.0
...
..
...
..
..
TABLEI1 workers with those obtained by us may be made in Table I. The lower melting form we obtained from RULESOF ISOROTATION APPLIEDTO PHENYLGLUCOSIDES a-naphthol was very labile; we have not been able AND PHENYL GLUCOPYRANOSIDURONIC ACIDS to transform the higher melting form to the lower melting form. The derivative obtained by us from (?-naphthol gave on hydrolysis the known 2- Phenyl a-n-glucopyrano~ide~ +46.300 +o4,700 +z7,90n -18,400 Phenyl ,%n-glucopyranoside7 naphthyl (?-D-glucopyranosiduronicacid. From reactions with phenol (procedures 3, 4 and Phenyl a-D-glucopyranosiduronic f(i3,903 + 1 7 , 0 3 5 +41,470 acid24 5 above) a second compound was isolated with melt- Phenyl 0-o-glucopyranosiduronic ing point 114-115' and [ a ] 2 a +157.50 ~ (c 1, CHC13). - 24,433 acid24 The dextrorotation and elementary analysis of this Phenyl tetra-0-acetyl-a-D-gluco+71,500 +81,010 +61.960 pyranoside" compound suggested that i t was the a-anomer. tetra-0-acetyl-QI-D-glucoCatalytic oxidation of phenyl a-D-ghcopyranoside Phenyl - 9.540 pyranoside: followed by esterification with diazomethane and XIethyl (phenyl tri-0-acetyl-a-o+S4,27.5 f 7 9 . 1 7 0 +49,980 acetylation gave authentic methyl (phenyl tri-0glucopyranosid)-uronate2' acetyl-a-D-ghcopyranosid) -uronate. The infrared Methyl (phenyl tri-0-acetyl-P-t-14.59.5 plucopyranosid)-uronate24 spectra of the compound as obtained by oxidation of the glucoside and as obtained from the fusion cation (25-50 g.) gives a product which is rather mixture are identkal. The free phenyl CY-D-gh- difficult to purify. The only other (?-D-glucopyrancopyranosiduronic acid which was obtained crys- osiduronic acid that has been isolated by de-esterifitalline by oxidation of the glucoside is, so far as cation is that of (?-naphthoLZ5 we know, the first aryl a-D-ghcopyranosiduronic The procedures used for obtaining aryl D-glUC0acid to be reported. pyranosiduronic acids necessitated easy availabilIn Table I1 are listed the molecular rotations of ity of the starting materials methyl (tri-O-acety1-athe acetylated phenyl glucopyranosides and the D-ghICOpyranOSyl bromide)-uronate and the acetylacetylated methyl esters of the phenyl glucopyran- ated methyl glucuronates. The latter are essential to osiduronic acids. B y applying Hudson's rule of the preparation of the acetobromo compound. isorotationZ1the 2A and 2B values for both sets of Methyl glucuronate has been prepared by the reacanomers were calculated. The 2A values (effect of tion of silver glucuronate with methyl iodidez6and phenyl a t carbon one) agree reasonably well in the by refluxing glucuronolactone with methanol for 3 two series. The significance of the 2B values must daysz7 (a, I +. 11). Both procedures are lengthy. necessarily await isolation of other aryl CY-D-glUC0- The procedure of Jansen and for the preparapyranosiduronic acid derivatives. tion of methyl galacturonate by the acid-catalyzed Free phenyl p-D-ghcopyranosiduronic acid18f22,23 reaction of galacturonic acid with methanol leads was obtained in crystalline form by de-esterification to extensive glycosidation and lactonization when of the acetylated methyl ester with barium meth- applied to glucuronic acid (I11 -+ IV). Eventually oxide. This procedure is quite satisfactory on a it was found that glucuronolactone could be esterismall scale (1-2 g. ester) but large scale de-esterifi- fied with methanol in the presence of base catalysts (18) D.V. Parke and R . T. Williams. Biochcm. J.,48, 621 (1951). (b, I + 11). Concurrent with use of this reaction a (19) E. D. S. Corner, F. S. Billett and L. Young, ibid., 66, 270 similar procedure was published by Touster and (1954). (20) D.Robinson, J. N. Smith and R. T . Williams, ibid., 60, 221
(1951). (21) C. S. Hudson, THISJ O U R N A L , 81, 60 (1909). (22) J . W.Porteous and R . T. Williams, BioChem. J , 44,46 (194Y) (23) G. A. Garton, D. Robinson and R . T . Williams. i b i d . . 46, 65 i11(49).
(24) This paper (25) M Berenbom and L Young, Bzochem J , 49, lh5 (1951) (26) W F Ooehel and I? H Babers I Riol C h e m , 106, fi3 (19.34) (27) W b Ooebel and b H Babers i b d 111, 347 i IY351 (281 E b Janseu and Rosie Jang, THISJ O U R N A L , 68 I475 ( 1 Y 4 0 )
3312
G. 9. BOLLENH.ICK, J. ti., LONG,D. G. BENJAMNANI) J. .I. LINDQUIST
Reynolds. 2' 'The differences in procedures are not significant. However, it is shown here that the base catalyst may be sodium methoxide, sodium hydroxide, triethylamine, tetraethvlammonium hydroxide or anion-exchange resin. The latter is especially useful for small scale preparations. Base-catalyzed esterification of glucuronolactone was unsuccessful when the alcohols were ethanol, benzyl alcohol or benzyl cellosolve (ethylene glycol monobenzyl ether). Sirupy esters were obtained using methyl cellosol\-e (ethylene glycol monomethyl ether) and ethylene glycol. Eoth esters were identified as crystalline acetates. Only one acetate of each ester was isolated. With ethylene glycol there is a possibility of obtaining a monoor diester. The crystalline acetate isolated was shown to be that of a monoester by reaction of silver glucuronate with ethylene iodohydrin and subsequent acetylation. h crystalline product so obtained was identical with the acetylated product isolated from the lactone--glycol reaction. From the silver glucuronateeethylene iodohydrin reaction mixture the anomeric ester was also isolated as a crystalline acetate. CHART1 GLUCVKOXIC ACID WITH hf ETH A N O L
SUMMARY O F REACTIONS OF
CHOHY I HCOH I ,
CHOH-7
I
CH'OH
HCOH
+
--
I ~ H Ti ~ O
I H oc I {
(a)
~
CH1[)H/(OH) ____1 (h!
HbOH
-
~
HCciFi
~
Hq-0
CHUCHjr HFOH
I>ERIVA1'IVES
CHOHi
I
I HCOH
I
I
HOCH
0
HC-
HC-O I
COOH
0-C=O
IV
111 CHOCHr
HCOH CH,UH/H
HOCH
I ----f
€IC011
I
Ire-----
o
COUCH \
Several catalysts for acetylation of methyl glucuronate were surveyed for highest possible vield. The yield of mixed acetates with pyridine was 75% ; with cold perchloric acid S57c. As reported by Goebel and BabersZ6 the acetylated P-form is r9il 0 Iq521
I w i i t e r anti \
I1 Ke\nold\
I
Hzd
c k ~ i , i
197, H i
L'oI. 77
sufficiently insoluble in cold solvents to give n o difficulty in isolation; the a-anomer is much more troublesome. The isolation of the latter was in]proved by using benzene--hexane as crystallizing medium. Yields of ester acetates are consistently between 75-S5yo based on starting lactone. Various methods were tried for the preparation of methyl (tri-0-acetvl-a-D-glucopyranosyl bromide ) uronate. Especially disappointing was the inability t o apply the short procedure of Ehrczai-Llartos and Korosy3'' which would circumvent isolation of intermediate acetates. The preferred procedure is the original (HBr in acetic acid) of Coebel a n d BabersZ6
Experimental Methyl Tetraacetyl Glucopyranuronates. ( 1) Acid-catalyzed Acetylation.-Glucuronolactone (17.6 g., 0.1 molc) was added to 100 ml. of methanol which contained 0.15 g."' of sodium methoxide. The mixture was stirred a t room temperature for 30 minutes at the end of which time all glucuronolactone had dissolved. After another 30 minutes the methanol was removed under reduced pressure (water pump, 10-12 mm., bath temperature 40'). The was dissolved in 68 ml. of acetic anhydride and a mixture of 0.3 ml. of perchloric acid in 10 mi. of acetic anhydride was added dropwise a t a rate such t h a t the reaction temperature never exceeded 40". After t h e reaction mixture had stood overnight a t room temperature an additional 0.1 ml. of perchloric acid was added and the solution stored in t h e refrigerator. Overnight 9.95 g. of crystalline material separated. I t was isolated by filtration followed by ether wash. The crystals were recrystallized once from hot ethanolyield 9.6 g. of methyl tetra-0-acetyl-p-D-glucopyranuronate; m.p. 176.8-178O; [ c Y ] ~ ~+7.4" D ( c 2, CHC1,); literature valuesz6 m.p. 178'; [ c Y ] ~ ~+8.7" D (c 1, CHCL). The mother liquor from the reaction was poured onto 300 g. of crushed ice and neutralized with sodium bicarbonate. After removal of excess sodium bicarbonate on a filter the cake and filtrate were extracted thoroughly with chloroform. The chloroform extract was dried with anhydrous sodium sulfate and concentrated t o a sirup which was taken U p in hot isopropyl alcohol. On cooling a 21.5-g. crop of crude crystalline material separated; [ c Y ] ~ ~fD 82" ( G 2, CHCla). Over-all yield (crude) was 83% of theory. The crude could he recrystallized best from benzene-hexane to gain a t least partial separation of anomers. ( 2 ) Pyridine-catalyzed Acetylation.-Sodium hydroxide (1.1 g.) was dissolved in 3 1. of methanol and 400 g. (2.27 moles) of glucuronolactone was added in 100-g. increments. (Lactone should dissolve almost immediately; additional base should he added if pH drops below 8.0.) T h e mixture was stirred 1 hr. a t room temperature and methanol was then removed under reduced pressure (water pump, 10-12 mm., bath temperature below 50"). Final methanol removal was accomplished with a vacuum pump. Acetylation was effected as above using 1 I. of pyridine and 1.5 I. of acetic anhydride. On standing in the refrigerator overnight 365 g. of methyl tetra-0-acetyl-P-D-glucopyranuronate crystallized from the reaction mixture. An additional 25 g . of P-isomer was obtained on concentration of the mixture. By processing mother liquors as above 242 g. of methyl tetra-0-acetyl-a-D-glucopyranuronate was obtained. 111 general, yields are in the neighborhood of 70%. Sodium hydroxide may be replaced by 40 ml. of 11"triethylamine in CHIOH, 1 g. of tetraethylammonium hydroxide or 40 ml. of N sodium rnethoxide. Acetoxyethyl Tetraacetyl Glucopyranuronates.-Piftee11 grams (0.085 mole) of glucuronolactone was added t o 75 ml. of ethylene glycol containing 1.5 ml. of '%1 sodium methoxide. Solution was instantaneous. After refrigeration over(30) ?rl. BArczai-Martos and F. Rcrosy, Nature, 165, 369 (1950). (31) Since glucuronolactone often contains glucuronic acid as a contaminant, it may be necessary t o use more sodium methoxide t o obtain the degree of alkalinity required. (32) If there is any uncertainty nbout the completeness of methyl ester formation this sirup should be taken up in absolute ethanol and rririgeratrrl 1 r n r e n r t e d yliiruronol;icf o n e will mi 5 t t i I l i x
Julie 20, 1955
SYNTHESIS OF ARYL-D-GLUCOPYKANOSIDURONIC ACIDS
night the base was neutralized with sulfuric acid and the solution concentrated a t 0.3 mm. (bath a t 37-45') to a very thick sirup. The sirup was dissolved in 100 ml. of pyridine and 100 ml. of acetic anhydride was added keeping solution temperature below 20". After refrigeration overnight solvents were removed under reduced pressure (water pump) and the residue evaporated under reduced pressure several times with 50-ml. portions of toluene. After addition of ethanol to the final sirup crystallization occurred, m.p. 135-138" (10.0 g., 26.3%). After several recrystallizations from ethanol or isopropyl alcohol t h e acetylated ester melted a t 139-140': [ a l Z 5 t 1~2 . 5 " IC 1. CHCl,). AnaZ.33 Calcd. for CI9H2401; (mbnoester): C, 48.21; H, 5.35. Found: C, 48.41: H~, . 5.23. Ten grams of ethl-lene i ~ d o h y d r i nand ~ ~ 1.89 g. (6.3 iumoles) of silver glucuronate2s were stirred together for 2 hrs. a t room temperature. The precipitate was collected on a filter and washed with ether t o remove as much excess ethylene iodohpdrin as possible. T h e gummy residue was triturated with water and then filtered free of silver iodide. A n excess of solid barium carbonate was added t o the aqueous iolution t o neutralize any free glucuronic acid. After removal of excess barium carbonate by filtration the filtrate was lyophilized and the residual sirup was triturated with ethanol. A small amount of insoluble barium salts separated and was removed by filtration. The filtrate was concentrated t o a sirup which was acetylated with 10 ml. of a 1: 1 pyridine-acetic anhydride mixture for 24 hr. a t room temperature. After processing in the usual manner the 2acetoxvethvl tetra-0-acetvl-B-D-ducoovranuronate crvstallized from isopropyl alcohol. TGe yield was 0.62 g. (22%); m.p. 138.5-140'; [(Y]"D 4-12.3' ( c 0.7, CHCls). Mixed melting point with the compound prepared above gave no depression. A n ~ 1 . 3 ~Calcd. for ClsHzrOla: C, 48.21; H , 5 . 3 5 . Found: C, 48.48, 48.33; H, 5.57, 5.47. After concentration and refrigeration of the mother liquor O.-ranosiduronic acid; m.p. 151.5-152 , [ c Y ] ~ ~ Dtheir appreciation of the able advice offered by Dr. -100' (c 1 , ethanol); literature valuesz5 m.p. 149-150". R. H. Tennyson during the course of this work. [ a ] * *-97" ~ (ethanol). Acknowledgment is also made to Mr. R. R. JohnMethyl (Methyl Gentisyl p-D-G1ucopyranosid)-uronate.son for general technical assistance. Two hundred me. (0.42 mmole) of methvl fmethvl nentisyl tri-O-acetylrp-D-glucopyranosid)-Uronate was dissorved (35) Methyl 8-D-glucofuranosidurono-y-lactone has about 15% the in 20 ml. of methanol and 0 . 2 ml. of 0.5 N barium meth- reduciog value of dextrose: Elizabeth M. Osman, K. C. Hobbs and oxide was added t o the solution. The solution was refrigW. E. Walston, THIS JOURNAL, 73, 2726 (1951). erated overnight and then treated with a calculated amount (36) J. E. Cadotte, F. Smith and D. Spriestersbach, i b i d . , 74, 1501 of sulfuric acid. Barium sulfate was removed b y filtration (1952). and the filtrate concentrated t o crystals. The crude ma(37) L. N. Owen, S. Peat and W. J. G. Jones, J. Chcm. Soc., 339 terial (120 mg., 82%) was recrystallized from ethanol a t (1951). room temperature to constant melting point 180-181.5', [.I]*~D -83.4 (c 1.4, CHIOH). 4 n e l . 3 3 Calcd. for C I , H ~ ~ - ARGO,ILLINOIS
[CONTRIBUTION FROM
THE
CEREALCROPSSECTION, NORTHERN UTILIZATION RESEARCH BRANCH '1
Preparation of Panose by the Action of NRRL B-512 Dextransucrase on a Sucrose-Maltose Mixture' BY MARYKILLEY, R . J. DIMLER AND J. E. CLUSKEY RECEIVEDNOVEMBER 12, 1954
A new method is presented for the preparation of panose involving the action of culture filtrates of Leuconostoc mesenteroides S R R L B-512, containing dextransucrase, upon a sucrose-maltose mixture. A preliminary study of the effects of variations in carbohydrate and enzyme concentration and in reaction temperature provided a basis for selection of suitable conditions for limiting the reaction mainly t o panose formation. The most important variable was found to be the ratio of maltoce t o sucrose, while the total carbohydrate concentration had a smaller but significant effect. The preparative procedure d e veloped included separation of the synthesized panose from the yeast-treated reaction mixture by chromatography on a carbon-Celite3 column. The resulting product crystallized readily and recrystallization did not change its properties.
Panose, a 4-a-isomaltopyranosyl-~-glucose, was crystallized first by Pan4 as a product of the (1) One of the Branches of the Agricultural Research Service, U. S. Department of Agriculture. Article not copyrighted. (2) Presented at the Midwest Regional Meeting of the American Chemical Society, Omaha, Nebr., Novemher, 1954. (3) Mention of firm names or trade products does not imply that they ere endorsed or recommended by the U. S . Department of Agriculture over other firms or similar products nut mentioned. (4) S. c. Pan. 1,. W Nichulnori and P K u l d c ~ h u vT. H I S r O I I H N A I . . 73. 2547 ( 1 9 6 1 ) .
transglucosylation action of an Aspergillus niger culture filtrate on maltose. From a DreDarative standpoint this method had the disadvantage t h a t the culture filtrate had to be freshly prepared in order to avoid marked decreases in the yield of panose. We present here an alternative method for Ilreparation of panose which this difficulty and which yields a product that does r i o t r r y uire recrystallization. I
,
