[CONTRIBUTION FROM THE CHEMISTRY LABORATORY, NATIONAL INSTITUTE OF HEALTH, u. s. PUBLIC HEALTH SERVICE]

VOLEMITOL HEPTAACETATE

W. DAYTON MACLAY, RAYMOND M. HA", AND C. S. HUDSON

Received March 16, 19.4.4

The literature concerning this substance is very confusing. Since we had occasion some years ago to prepare it, the following description of itEi properties is published, with a historical preface that will elucidate, we believe, the curious mistakes of identity that are now known with certainty to be present in some of the records concerning it.

Bourquelot (1) discovered volemitol in a somewhat rare species of mushroom, Lactarius volemus Fr., which also contains D-mannitol, the hexitol that has been found in most mushrooms. At that time the m.p. 166" had been established for mannitol, and for mannitol hexaacetate the existing data were near those now accepted, which are m.p. 123" and [aylD 4-25' in chloroform and +18.8" in glacial acetic acid. The m.p. which Bourquelot found for volemitol was 140-142") which showed i t to be a different substance from mannitol; its crystals were also different in appearance, and it was much more soluble than mannitol. These characteristics, together with others that may be passed over for brevity, con- vinced Bourquelot that he had in hand a new polyhydroxy alcohol, a relative of mannitol, and he named i t volemitol. He acetylated a sample of volemitol (which became known later to have been impure because subsequent researches established the m.p. of pure volemitol as 153-154') and obtained in low yield a crystalline acetate, m.p. 119" and [a], +19.1" in "acide acetique". He remarked that, its properties closely resemble those of mannitol hexaacetate.

The number of carbon atoms in the molecule of volemitol was not known at that time. Mannitol had long been recognized as a hexitol, through its reduction by hydriodic acid and phosphorus to a hexyl iodide (2). Perseitol, a polyhy- droxy alcohol which had been discovered (3) in Persea gratissima Gaert. and long thought to be a hexitol, had been shown by Maquenne (4) through the analysis of several of its derivatives (especially dibenzylideneperseitol), to be a heptitol. Fischer's phenylosazone researches had disclosed a simple way to determine the length of the carbon chain in such polyhydroxy alcohols and his method could be used with moderately small amounts of substance. Bourquelot applied to him for a decision regarding the molecular formula of volemitol, sending him 10 g. of the rare substance. Fischer (5) found the m.p. after four recrystallizations of the sample from hot alcohol to be 151-153" (corr.) with sintering at 147". [We remark a t this point that Fischer's data furnish an early indication of the fact, which became well established later, that it is very difficult to obtain volemitol free from other alcohols (in this case mannitol) simply by repeated recrystalliza- tions.] Fischer oxidized the sample with hypobromite and prepared from the product through reaction with phenylhydrazine a crystalline substance, named by him phenylvolemosazone, the analysis of which for carbon, hydrogen, and nitrogen proved beyond question that i t was a phenylheptosazone and that volemitol was accordingly a heptitol. This decision not only confirmed Bour-

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294 W. D. MACLAY, E. 11. H h S N AKD C. S. HUDSON

quelot's recognition of volemitol as a different alcohol from mannitol, i t also brought into clearer recognition the fact that a t least five classes of non-cyclic polyhydroxy alcohols exist in wide distribution in nature, namely, the three- carbon glycerol, the four-carbon erythritol (a constituent of lichens), the five- carbon adonitol (from Adonis vernalis L.), the six-carbon mannitol, sorbitol, and dulcitol, and the seven-carbon perseitol and volemitol.

Seven years later Bougault and Allard (6) isolated voleniitol from three species of primrose (Primula grandiflora L., clatior Jacq., and oficinalis Jacq.), identify- ing i t by comparison with a sample of volemitol from Bourquelot, prepared from Lactarius volemus. They recrystallized volemitol to full purity (m.p. 154") and prepared several derivatives, among which was its heptaacetate, for which they found the m.p. 63" but did not record its rotation. They expressed the opinion that the acetate of m.p. 119" which Bourquelot had believed to be volemitol acetate was really mannitol hexaacetate, resulting from the presence of some mannitol in Bourquelot's early samples of volemitol (map. 140-142"). As Bourquelot aided the work of Bougault and Allard, it appears that he agreed with their conclusion regarding the acetate since no dissent is recorded. Bou- gault and Allard's work showed that it is very dimcult to free volemitol from mannitol even when one knows the identifying characteristics of the pure sub- stances; i t became obvious that Bourquelot's original discovery of volemitol was remarkable. Remarkable not because so excellent an experimentalist as Bour- quelot had failed to obtain i t in full purity, but because he had shown such great skill in recognizing i t a t all. It seemed now definitely settled that volemitol heptaacetate is a crystalline substance of m.p. 63"; and thus the matters stood for twenty-seven years. Then Ettei (7) began a study of volemitol, which he prepared from Lactarius volemus, a research which led him in three years to his establishment of the configuration of sedoheptulose through precise theoretical interpretation of his patient experimental studies (7b). As a minor part of these, which has no bearing on his real and permanent contribution, he prepared what he believed to be volemitol heptaacetate (7a), and he found m.p. 120-121" and [aID +20.7" in chloroform, values which confirmed Bourquelot's early data and indicated that Bourquelot's acetate was not mannitol hexaacetate after all. To some of us who mere following the ramifications of this recondite subject i t seemed that Ettel's result settled the question again. Apparently either Bou- gault and Allard had made an error, or their volemitol acetate of reported r n . ~ . 63" was a dimorphic form of Bourquelot's acetate. Accordingly, the reader can imagine our interest six years ago when me acetylated 2.0 g. of carefullypurified synthetic volemitol (D-manno-D-talo-heptitol) with 8 cc. of acetic anhydride and 0.5 g. of sodium acetate and obtained in nearly quantitative yield and high purity Bougault and Allard's volemitol hexaacetate of m.p. 63". I ts rotation, non- published for the first time, is +36.1" (c, 2.0) in chloroform, and +30.8" (c, 0.8) in glacial acetic acid. This proves that the substance is not a dimorphic form of the acetate that Bourquelot and Ettel described, which rotated eleven degrees lower. Our initial interest now changed to surprise and we studied the

VOLEXITOL HEPTAACETATE 295

mal erial with special attention. Recrystallization of our product from 150 parts of hot water did not change its properties. Its deacetylation produced in nearly quantitative yield pure volemitol (m.p. 153"). Its analysis agrees with the formula of a heptitol heptaacetate (theory, c', 49.79, H, 5.97; CH3C0, 59.-19; foiind, C, 49.66; H, 6.18, CHJCO, 59.54). It was also obtained from a sample of natural T oleniitol hich was kindly supplied by Dr. C. Jelleff C'arr, \rho had isolated it from Primula roots. T'olemitol heptaacetate crystallizes from either hot \later, in 11-hich it is sparingly soluble, or from 20 parts of 8 5 v al- cohol, as clear well-built crystals 11-ith six faceh prominent, approximately rec- tangular prisms somen-hat elongated. I t is unquestionably the acetate which Boiigalt and -4llard discovered, and we agree ivith them that in all probability Boiirquelot'h data apply to mannitol hexaacetate. Ettel's article ( ia ) shon s that he had pure volemitol in hand (m.p. 153") during his studiec: the present evidence leads 11s to believe that an impure sample of the natural product, one containing some mannitol, was used for his acetylation experiment, and that his data agree \I ith those of Bourquelot because both observers measured mannitol he\.aacetate believing it to be the fully acetylated derivative of volemitol. .is an aid to future investigations, crystals of D-voleniitol heptaacetate and D-man- nitol hexaacetate are illustrated in Plates I and 11.

The description of the unusual history of volemitol and its heptaacetate leads to the surmise that this alcohol may be of far wider distribution in nature than hah been reported. So far mannitol has always been found associated with it, and mannitol is of very wide distribution. Can it be that volemitol and nian- nitol are frequently associated where only mannitol has been reported? The historical record leads one to believe that small amounts of volemitol in associa- tion with mannitol, perseitol, or sorbitol mould have escaped detection in past researchcis on plant constituents. It seems reasonable t o assume that the dis- coT-ery of volemitol in Lacfaritis rolemtis and in Primula species \\-as facilitated by a favorable proportion of it or some other factor which aided its initial crystal- 1iz:ition. It forms mixed crystals with mannitol and also xi th perqeitol; possibly the. careful study of crude crystalline mannitol from various natnral sources, by thv methods that have been disclosed in the researches on volemitol, will lead to its recognition in many other natural products. -Any wholly crystalline sample of natural mannitol which shows a depressed melting point should be suspected of containing volemitol, especially if it proves difficult to raise the m.p. to 166' by recrystallization. The known seven-carbon alcohols and sugars of nature (D-perseitol, D-volemitol, D-mannoheptulose, D-sedoheptulose, and L-perseulose) constitute a biological group, a discussion of which will be included in review papers from this laboratory by Dr. S. I<. Richtniyer and by one of the writers (C. S. H.).

There will now be described the procedure which was devised to obtain pure rolemitol from the mixture of it with D-perseitol that results from the reduction of D-mannoheptulose; the directions may prove helpful in the detection of vo- lernitol in plants.

296 W. D. MACLAY, R. M. HANN AND C. S. HUDSON

VOLEMITOL HEPTAACETATE 297

The reduction of D-rnannoheptulose. A solution of the ketose (25 g.) in water (70 cc.) was agitaxed in the bomb with 3 g. of Raney nickel and hydrogen (130 atmos.) for six hours a t 98". The Fehling test was negative. Removal of the catalyst, treatment of the solution with hydrogen sulfide to precipitate a small amount of heavy metals, filtration, and concen- tration to dryness gave a crystalline residue. It was dissolved in SO cc. of water, 100 cc. of 9570 alcohol was added, and a crop of perseitol was filtered off, wt. 11.25 g. The filtrate was concentrated to dryness, the residue was dissolved in 16 cc. of water and hot 95% alco- hol (64 cc.) was added; crystallization in the refrigerator yielded 9.5 g. of material which melted a t 140-142" (white, indicating presence of some perseitol). The filtrate from these crystals \\-as concentrated to dryness and dissolved in 10 cc. of boiling 85% alcohol, yielding a smrill crop of crystals of m.p. 143-145" (white). Previous attempts to separate the low- melting material by further recrystallizations had failed. The combined material of m.p. 140-145" mas shaken with 2 parts of benzaldehyde and 2 parts of 50yo sulfuric acid, the crystalline tribenzylidenevolemitol (SOYo yield) was filtered off, washed with water and bicarbonate solution, and recrystallized from 100 parts of 95oj, alcohol, yield SO%, m.p. 155-162". A second recrystallization of this product from 200 parts of absolute alcohol gave a yield of 75y0, m.p. 190-192'. Ettel (7) has shown that this benzylidenevolemitol material is a mixture of a t least two acetals; the separation of it into components is not necessary for the present objective, and the two recrystallizations suffice for removing perseitol. The benzylidenevolemitol was next hydrolyzed by refluxing for three hours with 18 parts of 4Y0 hydrochloric acid;' the benzaldehyde was removed by extraction with ether, the hydrochloric acid by silver carbonate, and traces of remaining silver in solution by hydrogen sulfide. The solution was concentrated to a dry crystalline solid; its crystalliza- tion from 20 parts of 85% alcohol gave a 60% yield of pure volemitol, m.p. 153-154". The over-all yield of pure volemitol from the crude material of m.p. 140-145" was thus about 247, ; this could doubtless be increased considerably by further experience.

BETHESDA, &ID.

REFERENCES (1) BOURQLELOT, J . pharm. chim., [6], 2, 389 (1895). (2) ERLENMEYER AND WANKLYN, Ann. , 136,129 (1865). (3) XVEQUIN, J. chim. mBd. pharm. tozicol., [l], 7,467 (1831). (4) RIAQUEWE, Compt. rend., 107, 583 (1888). (5) I:. FISCHER, Ber., 28, 1973 (1895). (6) I~OUGAIJLT AND ALLARD, Compt. rend., 136,796 (1902); Bull. soc. chim., [3], 29,129 (1903);

(7) ETTEL, (a) Collection Czechoslov. Chem. Commun., 1, 288 (1929); (b) 4, 504, 513 (1932). (8) MEUNIER, Compt. rend., 107,910 (1588).

J . pharm. chim., [6], 16, 528 (1902).

'While preparing this article we noticed a remark by J. Meunier (8) which had escaped our attention during our experimental work; it is possible that the benzylidenevolemitol can be hydrolyzed under much milder conditions than we used, provided some excess benzal- dehyde i s present as a second liquid phase.