Chemistry

G. A. Serebrennikova, T. K. Mitrofanova, A. A. Kraevskii,
I. K. Sarycheva, and N. A. Preobrazhenskii

Complete Synthesis of the Triglycerides of Soybean Oil

(Presented by Academician A. N. Nesmeyanov, April 28, 1961)

The glycerides of soybean oil, according to data from physicochemical methods of analysis, contain, in various combinations, residues of linolenic, linoleic, oleic, stearic, and palmitic acids. The experimentally determined glyceride structure of the oil \((^{1})\) agrees with the results obtained on the basis of distribution theory \((^{2})\). In order to refine the glyceride composition of soybean oil and to study physicochemical properties, we synthesized triglycerides with allowance for possible positional isomers (scheme 1). Starting from isopropylideneglycerol, we obtained 5 monoglycerides: \(\alpha\)-monolinolenin (XLVI), \(\alpha\)-monolinolein (XLVII), \(\alpha\)-monoolein (XLVIII), \(\alpha\)-monostearin (XLIX), and \(\alpha\)-monopalmitin (L). Conversion of the latter into triglycerides was carried out either in one stage: \(\alpha\)-linolenoyl-\(\beta,\alpha'\)-distearin (VII), \(\alpha\)-linoleoyl-\(\beta,\alpha'\)-distearin (XVI), \(\alpha\)-linoleoyl-\(\beta,\alpha'\)-dipalmitin (XVII), triolein (XXVII), \(\alpha\)-oleoyl-\(\beta,\alpha'\)-distearin (XXVIII), \(\alpha\)-stearoyl-\(\beta,\alpha'\)-diolein (XL), tristearin (XLI), \(\alpha\)-palmitoyl-\(\beta,\alpha'\)-dilinolenin (XLII), \(\alpha\)-palmitoyl-\(\beta,\alpha'\)-dilinolein (XLIV), tripalmitin (XLV), or in two stages: \(\alpha\)-oleoyl-\(\beta\)-stearoyl-\(\alpha'\)-linolein (XXIII), \(\alpha,\alpha'\)-dioleoyl-\(\beta\)-stearin (XXVI), \(\alpha\)-stearoyl-\(\beta\)-oleoyl-\(\alpha'\)-linolein (XXXIV), \(\alpha\)-stearoyl-\(\beta\)-linoleoyl-\(\alpha'\)-olein (XXXVI), \(\alpha,\alpha'\)-distearoyl-\(\beta\)-linolenin (XXXVII), \(\alpha,\alpha'\)-distearoyl-\(\beta\)-linolein (XXXVIII), \(\alpha,\alpha'\)-distearoyl-\(\beta\)-olein (XXXIX), \(\alpha\)-palmitoyl-\(\beta\)-linoleoyl-\(\alpha'\)-linolein (XLIII), via \(\alpha,\alpha'\)-diglycerides: \(\alpha\)-oleoyl-\(\alpha'\)-linoleoylglycerol (LI), \(\alpha,\alpha'\)-dioleoylglycerol (LII), \(\alpha\)-stearoyl-\(\alpha'\)-linoleoylglycerol (LIII), \(\alpha\)-stearoyl-\(\alpha'\)-oleoylglycerol (LIV), \(\alpha,\alpha'\)-distearoylglycerol (LV), and \(\alpha\)-palmitoyl-\(\alpha'\)-linoleoylglycerol (LVI).

The triglycerides obtained were purified by adsorption chromatography on silicic acid, and paper chromatography was used for their identification. The physicochemical data for the triglycerides are presented in Table 1.

The triglycerides trilinolenin (I), \(\alpha,\alpha'\)-dilinolenoyl-\(\beta\)-linolein (II), \(\alpha,\alpha'\)-dilinolenoyl-\(\beta\)-olein (III), \(\alpha,\alpha'\)-dilinolenoyl-\(\beta\)-stearin (IV), \(\alpha\)-linolenoyl-\(\beta,\alpha'\)-dilinolein (V), \(\alpha\)-linolenoyl-\(\beta,\alpha'\)-diolein (VI), \(\alpha\)-linoleoyl-\(\beta,\alpha'\)-dilinolenin (VIII), trilinolein (IX), \(\alpha\)-linoleoyl-\(\beta\)-oleoyl-\(\alpha'\)-linolenin (X), \(\alpha\)-linoleoyl-\(\beta\)-stearoyl-\(\alpha'\)-linolenin (XI), \(\alpha\)-linoleoyl-\(\beta,\alpha'\)-diolein (XII), \(\alpha,\alpha'\)-dilinoleoyl-\(\beta\)-linolenin (XIII), \(\alpha,\alpha'\)-dilinoleoyl-\(\beta\)-olein (XIV), \(\alpha,\alpha'\)-dilinoleoyl-\(\beta\)-stearin (XV), \(\alpha\)-oleoyl-\(\beta,\alpha'\)-dilinolenin (XVIII), \(\alpha\)-oleoyl-\(\beta\)-linoleoyl-\(\alpha'\)-linolenin (XIX), \(\alpha\)-oleoyl-\(\beta\)-stearoyl-\(\alpha'\)-linolenin (XX), \(\alpha\)-oleoyl-\(\beta,\alpha'\)-dilinolein (XXI), \(\alpha\)-oleoyl-\(\beta\)-linolenoyl-\(\alpha'\)-linolein (XXII), \(\alpha,\alpha'\)-dioleoyl-\(\beta\)-linolenin (XXIV), \(\alpha,\alpha'\)-dioleoyl-\(\beta\)-linolein (XXV), \(\alpha\)-stearoyl-\(\beta,\alpha'\)-dilinolenin (XXIX), \(\alpha\)-stearoyl-\(\beta\)-linoleoyl-\(\alpha'\)-linolenin (XXX), \(\alpha\)-stearoyl-\(\beta\)-oleoyl-\(\alpha'\)-linolenin (XXXI), \(\alpha\)-stearoyl-\(\beta,\alpha'\)-dilinolein (XXXII), \(\alpha\)-stearoyl-\(\beta\)-linolenoyl-\(\alpha'\)-linolein (XXXIII), \(\alpha\)-stearoyl-\(\beta\)-linolenoyl-\(\alpha'\)-olein (XXXV), which are present in both soybean and linseed oil, were obtained by us previously \((^{3})\).

The synthesized triglycerides (I–XLV), in their properties, are close to natural—

to soybean oil: \(d_4^{20}\ 0.921—0.931,\ n_D^{20} 1.472—475\). Iodine value 114—137. The principal starting substances in the synthesis of triglycerides of linseed, walnut, sunflower, soybean, sesame, olive, almond, coconut oils, cocoa-bean oil, butter, egg-yolk fat, and other vegetable oils and animal fats are higher acids of the aliphatic series.

The literature contains descriptions of a number of methods for obtaining linoleic \((^{4})\), linolenic \((^{5})\), and other higher fatty acids. Owing to low yields, experimental difficulties, or the absence of accessible raw materials, these methods are, for the most part, of only theoretical interest.

We investigated several possible routes for obtaining higher fatty acids on the basis of products of ethylene telomerization \((^{6})\), butadiene polymerization \((^{7})\), and other available types of raw materials \((^{8})\). The present article gives one of the methods for obtaining linolenic acid, which is also applicable to other compounds of this series.

Octyn-2-ol-1 (LVII, b.p. 98—100°/16 mm, \(d_4^{20}\ 0.8916,\ n_D^{20}\ 1.4551,\ MR_D\ 38.37.\ \mathrm{C_8H_{14}OF}\). Calculated 38.61), obtained by condensation of butyl bromide and 1-chlorobutyn-2-ol-4, is converted by reaction with phosphorus tribromide into 1-bromooctyne-2 (LVIII). Yield 80.4%. B.p. 69—72°/5 mm, \(d_4^{20}\ 1.2095,\ n_D^{20}\ 1.4859,\ MR_D\ 44.88.\ \mathrm{C_8H_{13}BrF}\). Calculated 44.84.

The second component, ethylene acetal of decyn-9-al-1 (LXII) \((^{13})\), was obtained from decadiene-1,9 (LIX, b.p. 76—77°/18 mm, \(d_4^{20}\ 0.8376,\ n_D^{20}\ 1.4532,\ MR_D\ 44.33.\ \mathrm{C_{10}H_{14}F_2}\). Calculated 44.25. IR spectrum 331 (s.), 2125 (m.) cm\(^{-1}\)), synthesized in 80.7% yield from 1,6-dibromohexane (b.p. 110.8—112°/14 mm, \(d_4^{20}\ 1.5737,\ n_D^{20}\ 1.5055,\ MR_D\ 45.49.\ \mathrm{C_6H_{12}Br_2}\). Calculated 45.44). Decadiene-1,9 (LIX) is converted by reaction with thioacetic acid into decyn-9-en-1-thiol-1 acetate (LX, yield 79.3%, b.p. 95.3—96.4° at 0.12 mm, \(d_4^{20}\ 0.9746,\ n_D^{20}\ 1.5022,\ MR_D\ 63.42.\ \mathrm{C_{12}H_{18}OSFF}\). Calculated 62.85), from which, via decyn-9-aldoxime-1 (LXI, yield 88.4%, m.p. 79.1—79.5°), ethylene acetal of decyn-9-al-1 (LXII) is obtained. Yield 67.1%.

B.p. 73.0—74.5°/16 mm, \(d_4^{20}\ 0.9504,\ n_D^{20}\ 1.4564,\ MR_D\ 56.93.\ \mathrm{C_{12}H_{20}O_2}\). Calculated 56.61.

\[ \begin{array}{lll} \mathrm{CH_3(CH_2)_3Br} & & \mathrm{HC{\equiv}C(CH_2)_6C{\equiv}CH} \\ \downarrow\ \mathrm{ClCH_2C{\equiv}CCH_2OH} & & \mathrm{LIX}\ \downarrow \\ \mathrm{CH_3(CH_2)_4C{\equiv}CCH_2OH} & & \mathrm{HC{\equiv}C(CH_2)_6CH{=}CHSCOCH_3} \\ \mathrm{LVII}\ \downarrow & & \mathrm{LX}\ \downarrow \\ \mathrm{CH_3(CH_2)_4C{\equiv}CCH_2Br} & \searrow & \mathrm{HC{\equiv}C(CH_2)_7CH{=}NOH} \\ \mathrm{LVIII} & & \mathrm{LXI}\ \downarrow \\ & & \mathrm{HC{\equiv}C(CH_2)_7CH\left(\begin{array}{c}\mathrm{O{-}CH_2}\\[-2pt]\mathrm{O{-}CH_2}\end{array}\right)} \\ & \swarrow & \mathrm{LXII} \\ \mathrm{CH_3(CH_2)_4C{\equiv}CCH_2C{\equiv}C(CH_2)_7CH\left(\begin{array}{c}\mathrm{O{-}CH_2}\\[-2pt]\mathrm{O{-}CH_2}\end{array}\right)} \\ \mathrm{LXIII}\ \downarrow \\ \mathrm{CH_3(CH_2)_4C{\equiv}CCH_2C{\equiv}C(CH_2)_7COOH} \\ \mathrm{LXIV}\ \downarrow \\ \mathrm{CH_3(CH_2)_4CH{=}CHCH_2CH{=}CH(CH_2)_7COOH} \\ \mathrm{LXV} \end{array} \]

Scheme for the synthesis of cis-, cis-octadecadiene-9,12-oic-1 acid

By condensation of 1-bromooctyne-2 (LVIII) with ethylene acetal of decyn-9-al-1 (LXII), ethylene acetal of octadecadiyn-9,12-al-1 (LXIII) is obtained. Yield 57.6%.

B.p. 142.9—144.1°/0.09 mm, \(d_4^{20}\ 0.9411,\ n_D^{20}\ 1.4789,\ MR_D\ 91.73.\ \mathrm{C_{20}H_{32}O_2F_2}\). Calculated 91.68. Subsequent saponification and oxidation of compound (LXIII) leads to octadecadiyn-9,12-oic-1 acid (LXIV). Yield 39.7%. M.p. 42.6—43.9° (from alcohol). \(R_f\ 0.84\), system \(n\)-butanol : chloroform : 25% aqueous ammonia (10 : 5 : 2).

Table 1

Scheme 1. Synthesis of soybean-oil glycerides

[The page contains a reaction scheme with compounds labeled (I)–(LXIV), showing triglyceride structures bearing acyl residues denoted P, S, Ol, L, and Ln.]

P—C₁₅H₃₁CO (palmitoyl)
S—C₁₇H₃₅CO (stearoyl)
Ol—C₁₇H₃₃CO (oleoyl)
L—C₁₇H₃₁CO (linoleoyl)
Ln—C₁₇H₂₉CO (linolenoyl)

By selective hydrogenation of octadeca-9,12-diynoic acid (LXIV), cis,cis-octadeca-9,12-dienoic acid, linoleic acid (LXV), is obtained. Yield 82.6%. B.p. 148.1–150.7°/0.21 mm, \(d_4^{20}\) 0.9122, \(n_D^{20}\) 1.4715, \(MR_D\) 86.10. \(C_{18}H_{32}O_2\). \(F_2\). Calculated 85.93. \(R_f\) 0.71, system n-butanol : 10% aqueous ammonia (9 : 2).

Found, %: C 77.36; 77.51; H 11.61; 11.63
\(C_{18}H_{32}O_2\). Calculated, %: C 77.11; H 11.50

Moscow Institute of Fine Chemical Technology
named after M. V. Lomonosov

Received
27 IV 1961

REFERENCES CITED

¹ C. R. Scholfield, M. A. Hicks, J. Am. Oil Chem. Soc., 34, 77 (1957).
² R. J. Vander Wal, J. Am. Oil Chem. Soc., 37, 595 (1960).
³ I. K. Sarycheva, G. A. Serebrennikova, E. N. Zvonková, G. K. Mitrofanova, M. E. Maurit, O. V. Utkina, N. A. Preobrazhenskii, DAN, 135, No. 3, 617 (1960).
⁴ H. W. Walborsky, R. H. Davis, D. R. Howton, J. Am. Chem. Soc., 73, 2590 (1951); J. M. Osbond, J. C. Wickens, Chem. and Ind., 41, 1288 (1959); J. M. Osbond, Proc. Chem. Soc., 1960, 221.
⁵ S. S. Nigam, B. C. L. Weedon, J. Chem. Soc., 1956, 4049.
⁶ A. N. Nesmeyanov, L. I. Zakharkin, Izv. AN SSSR, OKhN, 1955, 224.
⁷ F. Sondheimer, V. Gaoni, J. Am. Chem. Soc., 82, 5765 (1960).
⁸ I. K. Sarycheva, G. I. Myagkova, N. A. Preobrazhenskii, ZhOKh, 29, 2318 (1959); R. O. Feuge, J. Am. Oil Chem. Soc., 37, 527 (1960).