Phenolic, Sulfur, and Nitrogen Compounds in Food Flavors

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Phenolic, Sulfur, and Nitrogen Compounds in Food Flavors Downloaded from pubs.acs.org by NATL UNIV OF SINGAPORE on 11/09/17. For personal use only.

F u r a n s S u b s t i t u t e d at t h e T h r e e P o s i t i o n w i t h S u l f u r WILLIAM J. EVERS, HOWARD H. HEINSOHN, JR., BERNARD J. MAYERS, and ANNE SANDERSON International Flavors and Fragrances, Inc., 1515 Highway 36, Union Beach, N. J. 07735

D u r i n g r e c e n t y e a r s the a n a l y s i s of cooked meats and of model systems has been r e p o r t e d by numerous investigators; leading references include Wilson et al ( 1 ) , Mussinan and K a t z ( 2 ) , Persson and von Sydow ( 3 ) , S c h u t t e ( 4 ) , and van den Ouweland and Peer ( 5 ) . We now r e p o r t the isolation, identification and s y n t h e s i s o f two important meat f l a v o r and aroma chemicals, 2 - m e t h y l - 3 - f u r a n t h i o l (1) and b i s (2-methyl-3furyl) disulfide (2).

2

1

While p r e p a r i n g s m a l l b a t c h e s (1000 g) of a p r o c e s s e d meat f l a v o r which c o n s i s t e d of a m i x t u r e of L c y s t e i n e h y d r o c h l o r i d e , thiamine c h l o r i d e h y d r o c h l o r i d e , h y d r o l y z e d v e g e t a b l e p r o t e i n and water heated at reflux for four hours (6), it was noted t h a t the c o n densate possessed an i n t e n s e r o a s t e d aroma. The material r e s p o n s i b l e f o r the aroma proved t o be e x t r a c t a b l e w i t h methylene c h l o r i d e but when the methylene c h l o r i d e was removed, o n l y a minute amount of m a t e r i a l remained. In o r d e r t o o b t a i n workable q u a n t i t i e s of aroma m a t e r i a l f o r a n a l y s i s a large scale preparation was u n d e r t a k e n . T h i s r e a c t i o n t o t a l e d 4,000 l b s . and gave 40 g a l l o n s condensate from which 16 liters of methylene c h l o r i d e e x t r a c t was o b t a i n e d . Careful s o l vent removal o f the e x t r a c t under m i l d vacuum and f i n a l c o n c e n t r â t i o n w i t h a stream of n i t r o g e n gave 184


11.

EVERS E T A L .

Furans Substituted

with

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50 ml of c o n c e n t r a t e p o s s e s s i n g a p o w e r f u l r o a s t aroma. T h i n - l a y e r chromatography of the c o n c e n t r a t e i n d i c a t e d the presence of a r e a d i l y i s o l a b l e compound near the s o l v e n t f r o n t . Repeated p r e p a r a t i v e t h i n l a y e r chromatography gave, from 2.4 g of c o n c e n t r a t e , a 66 mg sample of the d i s u l f i d e 2. The s t r u c t u r e i s a s s i g n e d on the b a s i s of mass s p e c t r a l , p r o t o n magnetic resonance and i n f r a r e d d a t a . When the c o n c e n t r a t e was s u b j e c t e d t o e x a m i n a t i o n by GLC, i t gave a s u c c e s s i o n of peaks b l e n d i n g i n t o a complex chromotogram. One p a r t i c u l a r s e c t i o n of the GLC e f f l u e n t when o r g a n o l e p t i c a l l y e v a l u a t e d had what was d e s c r i b e d as a pot r o a s t " type aroma. I s o l a t i o n of the compound or com pounds r e s p o n s i b l e f o r t h i s odor was u n d e r t a k e n . As a r e s u l t of r e p e a t e d t r a p p i n g and rechromatography i t became apparent t h a t the pot r o a s t compound was p r e s e n t i n v e r y minute amounts. With much t r i a l and e r r o r , a scheme f o r the i s o l a t i o n of t h i s compound was worked o u t . T h u s , from 4 ml of c o n c e n t r a t e we o b t a i n e d 2 - 3 λ of the f u r a n t h i o l 1. As i n the c a s e of the d i s u l f i d e , the s t r u c t u r e proposed was based on mass s p e c t r a l , p r o t o n magnetic resonance and i n f r a r e d d a t a . In o r d e r t o c o n f i r m the proposed s t r u c t u r e s of 1 and 2, t h e i r s y n t h e s i s was u n d e r t a k e n and i s o u t l i n e d i n Table I. S u l f o n a t i o n of 5 - m e t h y l - 2 - f u r o i c a c i d (3) w i t h fuming s u l f u r i c a c i d gave the known 2 - m e t h y l 3 - s u l f o - 5 - f u r o i c a c i d (4) (7) which was d e c a r b o x y l a t e d with mercuric c h l o r i d e to y i e l d 2 - m e t h y l - 3 - f u r a n s u l f o n i c a c i d (5). Treatment of 5 w i t h t h i o n y l c h l o r i d e gave the s u l f o n y l c h l o r i d e 6, which was reduced w i t h l i t h i u m aluminum h y d r i d e , g i v i n g 2 - m e t h y 1 - 3 - f u r a n t h i o l (1). T h i s m a t e r i a l has an i d e n t i c a l mass s p e c t r u m , p r o t o n magnetic resonance and i n f r a r e d spectrum as the m a t e r i a l s i s o l a t e d from the r e a c t i o n meat f l a v o r . Oxi d a t i o n of 1 w i t h i o d i n e gave b i s ( 2 - m e t h y l - 3 - f u r y l ) d i s u l f i d e (2) which a l s o has i d e n t i c a l s p e c t r a l p r o p e r t i e s as the i s o l a t e d m a t e r i a l . These s y n t h e s e s thus c o n f i r m the s t r u c t u r e s proposed from the a n a l y t i c a l d a t a f o r the i s o l a t e d m a t e r i a l s (8). S i m i l a r compounds were s y n t h e s i z e d i n o r d e r t o compare the f l a v o r p r o p e r t i e s of t h e s e compounds. The c o r r e s p o n d i n g 2 , 5 - d i m e t h y l - 3 - f u r a n t h i o l (8) was p r e pared by h y d r o l y s i s of 2 , 5 - d i m e t h y l - 3 - t h i o a c e t y l f u r a n (7)(10). Treatment of 2 , 5 - d i m e t h y l f u r a n w i t h e i t h e r s u l f u r m o n o c h l o r i d e or s u l f u r d i c h l o r i d e gave, i n low y i e l d , a m i x t u r e c o n t a i n i n g both b i s ( 2 , 5 - d i m e t h y l - 3 f u r y l ) s u l f i d e (10c) and b i s ( 2 , 5 - d i m e t h y l - 3 - f u r y l ) d i sulfide (lOd). The c o r r e s p o n d i n g t r i - and t e t r a s u l f i d e s of 2 were a l s o p r e p a r e d . Thus the r e a c t i o n of 1 11

PHENOLIC, SULFUR, A N D NITROGEN COMPOUNDS I N FOOD FLAVORS


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w i t h s u l f u r d i c h l o r i d e gave b i s (2-methyl-3-furyl) t r i s u l f i d e (10a) and the r e a c t i o n of 1 w i t h s u l f u r m o n o c h l o r i d e gave b i s ( 2 - m e t h y 1 - 3 - f u r y 1 ) t e t r a s u l f i d e (10b). For comparison, 5 - m e t h y l - 2 - f u r a n t h i o l (12) and b i s ( 5 - m e t h y l - 2 - f u r y l ) d i s u l f i d e (13) were prepared. Treatment of the l i t h i o d e r i v a t i v e of s y l v a n (U) w i t h s u l f u r gave the t h i o l 12 which was o x i d i z e d w i t h i o d i n e t o g i v e 13.

11

12

13

A summary o f the o r g a n o l e p t i c e v a l u a t i o n s of the v a r i o u s compounds i s c o n t a i n e d i n T a b l e I I . It i s apparent from a b r i e f s t u d y of the t a b l e t h a t a l l of the f u r a n s where the s u l f u r atom i s bound t o the β c a r b o n have meaty aroma and t a s t e c h a r a c t e r i s t i c s . However, when the s u l f u r atom i s i n the a p o s i t i o n o n l y hydrogen s u l f i d e l i k e , burnt and c h e m i c a l n o t e s are o b s e r v e d . It i s somewhat s u r p r i s i n g t h a t a one c a r b o n s h i f t i n s u b s t i t u t i o n would produce t h i s s u b s t a n t i a l change i n f l a v o r c h a r a c t e r . Experimental I s o l a t i o n of 1 and 2. In a s u i t a b l e v e s s e l a m i x t u r e o f 35 l b s . of t h i a m i n e c h l o r i d e h y d r o c h l o r i d e , 35 l b s . of L - c y s t e i n e h y d r o c h l o r i d e , 1,238 l b s . of v e g e t a b l e p r o t e i n h y d r o l y s a t e ( c a r b o h y d r a t e f r e e ) and 2,692 l b s . of water was heated a t r e f l u x f o r f o u r h o u r s . A f t e r 45 m i n u t e s , 40 g a l l o n s of condensate was removed d u r i n g 3^ h r s . Each g a l l o n was e x t r a c t e d w i t h 400 ml of CHgClg e x t r a c t s were combined and d r i e d w i t h sodium s u l f a t e . S o l v e n t removal i n m i l d (100 mm) vacuum and f i n a l c o n c e n t r a t i o n w i t h a stream of dry n i t r o g e n gave 50 ml o f c o n c e n t r a t e . 2 - M e t h y l - 3 - f u r a n t h i o l (1) : P r e p a r a t i v e GLC of the c o n c e n t r a t e ( 2 x 2 ml) on an 8' χ 3/4", 25% SE 30 on A/W DMCS column, programmed from 7 0 ° t o 2 2 5 ° C at l ° / r a i n y i e l d s about 300 λ c o n t a i n i n g a s t r o n g pot r o a s t aroma. Rechromatography of the 300 λ on a 10 χ 3/8", 20% CBW 20M A/W DMCS column programmed from 8 0 ° t o 2 2 5 ° C at l ° / m i n y i e l d s about 100 λ of m a t e r i a l c o n t a i n i n g a v e r y i n t e n s e pot r o a s t aroma. F i n a l chromato graphy of t h i s m a t e r i a l on a 10 χ 1/4" g l a s s , 20% Apiezon L column gave 2-3 A of 2 - m e t h y l - 3 - f u r a n t h i o l a

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189

h a v i n g : i r ( n e a t , ΚBr p l a t e s ) 3120, 2960, 2925, 2540 ( - S H ) , 1595, 1514, 1222, 1136, 1092, 938, 888 and 730 cm ; nmr ( C C 1 ) 8 2.32 ( s , 3 , a r i n g CHo), 2 . 4 7 ( s , l β S H ) , 6.19 ( d , l , J = 1 . 5 H z , β r i n g Η ) , 7715 ppm ( d , l , J=1.5Hz, a r i n g Η ) ; mass spectrum (70 ev) m/e ( r e l . i n t e n s i t y ) 116 ( 5 ) , 115 ( 8 ) , 114 ( 1 0 0 ) , 113 ( 2 9 ) , 86 ( 1 0 ) , 85 ( 2 3 ) , 71 ( 1 4 ) . bis (2-Methyl-3-furyl) d i s u l f i d e (2): Repeated p r e p a r a t i v e t h i n - l a y e r chromotography on 8" χ 8" p l a t e s c o a t e d w i t h 1.25 mm o f s i l i c a - g e l G (200 X p o r t i o n s per p l a t e , developed w i t h 1:10 e t h e r / h e x a n e ) gave from 2 . 4 g o f c o n c e n t r a t e 0.066 g o f b i s ( 2 - m e t h y 1 - 3 - f u r y l ) d i s u l f i d e h a v i n g : i r ( n e a t , ΚBr p l a t e s ) 3120, 2955, 2920, 1580, 1512, 1222, 1120, 1085, 936, 885, 730 c m " ; nmr ( C C 1 ) * 2 . 0 8 ( s , 3 , a r i n g CHo), 6.27 ( d , 1 , J = 1 . 5 H z , β r i n g H ) , and 7.16 ppm ( d , l , J = 1 . 5 H z , a r i n g Η ) ; mass spectrum (70 ev) m/e ( r e l i n t e n s i t y ) 228 ( 6 ) , 227 ( 9 ) , 226 ( 6 0 ) , 115 ( 5 ) , 114 ( 1 7 ) , 113 ( 1 0 0 ) , 85 ( 1 3 ) . 2-Methyl-3-sulfo-5-furoic acid (4): The barium s a l t of 4a was prepared i n 93% y i e l d from 3 a c c o r d i n g t o S c u l l y and Brown ( 7 ) . The f r e e a c i d was i s o l a t e d f o r nmr by t r e a t i n g the barium s a l t w i t h HgSO^ f o l l o w e d by f i l t r a t i o n and e v a p o r a t i o n under vacuum. Nmr ( D 0 ) $ 2 . 6 2 ( s , 3 , a r i n g CHg) and 7.47 ppm ( s , l , β r i n g H) . 2-Methyl-3-furansulfonic acid (5): A s o l u t i o n of 33 g o f the barium s a l t o f 4a i n 450 ml o f HoO was t r e a t e d w i t h 20% H S 0 u n t i l no f u r t h e r p r e c i p i t a t i o n was o b s e r v e d . A f t e r f i l t r a t i o n , the f i l t r a t e was a d j u s t e d t o pH 7 w i t h s o l i d NaHCOg. A f t e r a d d i t i o n of 26.3 g o f m e r c u r i c c h l o r i d e the r e s u l t i n g m i x t u r e was heated at r e f l u x and m o n i t o r e d f o r C 0 e v o l u t i o n . When C 0 e v o l u t i o n had s t o p p e d , the m i x t u r e was c o o l e d t o room temperature and t r e a t e d w i t h hydrogen s u l f i d e . A f t e r standing overnight p r e c i p i t a t e d mercuric s u l f i d e was removed by d é c a n t a t i o n and f i l t r a t i o n . The s o l u t i o n was e v a p o r a t e d t o d r y n e s s iri vacuo and the r e s i due r e c r y s t a l l i z e d from a minimum of b o i l i n g water t o g i v e 4 . 2 5 g o f 2 - m e t h y 1 - 3 - f u r a n s u l f o n i c a c i d as the sodium s a l t . Ir ( n u j o l m u l l ) 3140, 1240, 1229, 1190, 1110, 1075, 1018, 898 cm"" ; nmr ( D „ 0 ) 6 2 . 4 8 ( s , 3 , a r i n g C H ) , 6.62 ( d , l , J = 2 H z , β r i n g Η) and 7.43 ppm (d,l,J-2Hz, a ring H). 2-Methyl-3-furansulfonyl chloride (6): A mix t u r e o f 80 g o f 5 (sodium s a l t ) , 880 g t h i o n y l c h l o r i d e and 15 drops o f d i m e t h y l formamide was heated a t r e f l u x f o r 100 m i n , c o o l e d t o room temperature and filtered. A f t e r washing the f i l t e r cake w i t h benzene (20 ml) and combining w i t h the f i l t r a t e , concentration i n vacuo gave 58 g o f a brown o i l . D i s t i l l a t i o n of the o i l gave 4 5 . 4 g o f 2 - m e t h y 1 - 3 - f u r a n s u f o n y l c h l o r i d e as a l i g h t y e l l o w l i q u i d b o i l i n g a t 5 5 ° C a t 0.55


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PHENOLIC, SULFUR, AND NITROGEN COMPOUNDS I N FOOD FLAVORS

t o r r . and h a v i n g : i r ( n e a t , ΚBr p l a t e s ) 3115, 1570, 1520, 1380, 1360, 1220, 1158, 1129, 1092, 1024, 948, 880, 740 c m " : nmr ( C C 1 ) 6 2.71 ( s , 3 , a r i n g CHo), 6.86 ( d , l , J - 2 H Z , β r i n g Η) and 7.52 ppm ( d , l , J = » 2 H z , a r i n g Η ) ; mass spectrum (70 ev) m/e ( d e c r e a s i n g i n t e n s i t y , m o l , ion) 145, 97, 53, 43, 180, and i n t e n s i t y of P+2 (182) i s 43% of P. 2 - M e t h y l - 3 - f u r a n t h i o l (1): A s o l u t i o n of 45.4 g of 2 - m e t h y l - 3 - f u r a n s u l f o n y l c h l o r i d e (6) i n 540 ml o f anhydrous e t h e r was added dropwise t o a s o l u t i o n of l i t h i u m aluminium h y d r i d e i n 1200 ml e t h e r . After h e a t i n g at r e f l u x one h o u r , e x c e s s h y d r i d e was d e s t r o y e d by the a d d i t i o n of e t h y l a c e t a t e . The r e s u l t i n g m i x t u r e was poured i n t o 1,500 ml water and the ether layer separated. The aqueous phase was e x t r a c t e d w i t h e t h e r (4 χ 250 ml) and the e t h e r e x t r a c t s were combined, washed w i t h 5% NaHCOg s o l u t i o n (150 m l ) , water (2 χ 200 ml) and d r i e d over sodium s u l f a t e . Sol vent removal i n vacuo gave 18 g crude 1 . Distillation gave 11.6 g of 2 - m e t h y 1 - 3 - f u r a n t h i o l b o i l i n g a t 575 8 . 5 ° at 36 t o r r and h a v i n g : i r , ( n e a t , KBr p l a t e s ) 3110, 2955, 2925, 2540 Î S H ) , 1594, 1512, 1223, 1134, 1092, 937, 889, 732 c m " ; nmr ( C C I . ) 6 2.34 (s,3, a r i n g CHo), 2.47 ( s , l , β r i n g S H ) , 6.19 ( d , l , J = 1 . 5 Hz, β r i n g H) and 7.15 ppm ( d , l , J - 1 . 5 H z , a r i n g H ) ; mass spectrum (70 eu) m/e ( r e l . i n t e n s i t y ) 116 ( 5 ) , 115 (8), 114 ( 1 0 0 ) , 113 (29), 86 (10), 85 (23), 71 (13). b i s (2-Methy1-3-fury1) d i s u l f i d e (2): A solution of 7.4 g of sodium h y d r o x i d e , 10 g of sodium c a r b o n a t e and 21 g o f 2 - m e t h y 1 - 3 - f u r a n t h i o l (1) i n 344 ml of water was p r e p a r e d . To t h i s s o l u t i o n was added a s o l u t i o n of 77.3 g of potassium i o d i d e and 23.2 g o f i o d i n e i n 780 ml o f water u n t i l the i o d i n e c o l o r p e r sisted f o r 1 m i n . A f t e r r e n d e r i n g the s o l u t i o n c o l o r l e s s w i t h 0.1 sodium t h i o s u l f a t e s o l u t i o n , the m i x t u r e wasextracted w i t h pentane (3 χ 150 m l ) . The pentane e x t r a c t s were combined, washed w i t h water (2 χ 100 ml) and d r i e d o v e r sodium s u l f a t e . S o l v e n t removal i n vacuo gave 10 g of an amber o i l . D i s t i l l a t i o n of the o i l gave 15.4 g of b i s ( 2 - m e t h y 1 - 3 - f u r y l ) d i s u l f i d e (2) b o i l i n g at 7 7 - 7 8 ° at 0.3 t o r r and h a v i n g : i r ( n e a t , KBr p l a t e s ) 3120, 2955^,2920, 1580, 1512, 1222, 1122, 1082, 938, 885, 730 cm ; nmr ( C C I . ) 1

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193

11. EVERS ET AL. Furans Substituted with Sulfur w i t h s a t . s a l t s o l u t i o n (4 χ 75 ml) and d r i e d (sodium sulfate). S o l v e n t r e m o v a l i n vacuo gave 26 g o f c r u d e 8 which on d i s t i l l a t i o n gave 17.3 g of 2 , 5 - d i m e t h y l 3 - f u r a n t h i o l b o i l i n g at 7 9 ° at 43 t o r r and h a v i n g : i r ( n e a t , KBr p l a t e s ) 3110, 2980, 2950, 2920, 2530, 1610. 1572, 1445, 1430, 1378, 1222, 1063, 982, 920, 790 c m " ; nmr ( C D C 1 ) 6 2.2 ( s , 3 , a r i n g C H o ) , 2.25 ( s , 3 , a r i n g C l i o ) , 2.59 ( s , 1, β r i n g SH) and 5 . 8 6 ppm ( s , l , β r i n g H ) ; mass spectrum (70 ev) m/e ( d e c r e a s i n g i n t e n s i t y , m o l , i o n ) 43, 128, 85, 127, 95, 113 (P+2 i n t e n s i t y 4.5% of P ) . 1


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Literature Cited and Notes 1.

Wilson, R.A., Mussinan, C.J., Katz, I . , and Sanderson, A. J. Agr. Food Chem., 21 (5) 873 (1973). 2. Mussinan, C.J., and Katz, I . , J. Agr. Food Chem., 21 (1) 49 (1973). 3. Persson, T . , and von Sydow, E., J. Food S c i . , 38, 379 (1973). 4. Schutte, L., C r i t . Rev. Food Technol. 458, Mar. 1974. 5. van den Ouweland, G.A.M., and Peer, H. G . , J. Agr. Food Chem., 23 (3) 501 (1975). 6. Giacino, C., U.S. Patent 3,394,015 (1968). 7. Scully, J.F., and Brown, E.V., J. Org. Chem.,19, 894 (1954). 8. The identification of 2-methyl-4-furanthiol has been reported by van den Ouweland and Peer (5) as one of the products from the reaction of H S and 4-hydroxy-5-methyl-3 (2H) dihydrofuranone. How ever, in the analytical data presented by these authors there is no mention of the intensity of the P+2 ion relative to the parent which would confirm the presence of sulfur and also in the infrared there is no l i s t i n g of absorbency near 2540 cm which is typical of a thiol function. Although the authors claim the structure by com parison of their spectra with those of a syn thesized reference compound, no details of the synthetic route are given. 9. Goldfarb, Ya. L. and Danyushevskii, Y a . L . , USSR Patent 157696, Oct. 14, 1963. 10. Evers, W.J., et a l , U.S. Patent 3,872,111 (1975). 2

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Phenolic, Sulfur, and Nitrogen Compounds in Food Flavors

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