synthesis of vitamin b6
TRANSCRIPT
-
7/26/2019 Synthesis of Vitamin B6
1/3
May, 1939
SYNTHESIS
OF
VITAMIN
B
6
1245
[ C O N T R I B U T I O N F R O M
TH E
R E S E A R C H L A B O R AT O R Y
OF
M E R C K
& Co., INC.]
Synthesis of Vitamin B
6
BY STANTON A.
H A R R I S
AN D
KARL FOLKERS
Th e str uc tur e of vit ami n B6 has been fully eluci
dat ed as 2-methyl-3-hydroxy-4,5-di-( hydroxy-
methyl)-pyridine, I, by the researches described in
the accompanying two papers
1
'
2
from this Lab
oratory, and also by the recent three papers of
Kuhn and his co-workers.
3-5
CH
2
OH
H o / ^ C H s O H
I
The complete synthesis of the vitamin B
6
, I,
has been accomplished also, and the authors
6
recently reported that the synthetic vitamin B
6
hydrochloride is chemically identical with the
natural vitamin B
6
hydrochloride a nd th at it is
biologically active.
This paper describes the details of the reactions
used for the synthesis of vitamin B
6
, and these may
be represented graphically in the following manner
vitamin B
6
not only produces a cure of the der
matitis but also a stimulation of growth.
10
I t
also has been found that a severe microcytic
hypochromic anemia developed in puppies when
the rat antidermatitis factor (vitamin B
6
) was
apparently the only missing component of the
diet. Thi s ane mia was cured by the additio n of
this factor to the diet.
11
A biological relat ionsh ip
between vitamin B
6
and unsat ura ted fatty acids
also has been studied, and recently Birch
12
suggested that the physiological function of
vitamin B
6
is connected with the utilization of
the unsaturated fatty acids.
The biological assay of the synthetic vitamin
B
6
,
which was performed in the Merck Institute
of Therapeutic Research by Dr. E. J. Reedman,
paralleled the results previously reported by
Keresztesy and Stevens
13
for the natural vitamin
B
6
,
a single dose of 100 gamma effecting a com
plete cure within fourteen days when fed to vita-
CD
CH
3
CCH
2
CCH
2
OC
2
H
6
+ CNCH
2
CN H
2
II
CH
2
OC
2
H
6
O
2
N(^NiCN
^ N -
VI
III
C
2
H
6
OH
-
Piperidine as
catalyst
CH,
CH2OC2HS
jCN
J=O
HN O
3
>
Ac
2
O
CH
2
OC
2
H
6
O
2
N / % C N
PCl
6
H
2
+ Pt
>
H
2
N
CHJ
CHaOCzHg
^ C N
Cl
H
2
+ Pt and
N/'
H
IV
CH
2
OC
2
H
6
H
1
N Z V H
2
N H J
\ N / -
H
V
=
'Chloro-
benzene
CH
2
OC
2
H
5
VII
Pd
charcoal
C H , ^
VIII
Isolated as
dipicrate
CH
2
OC
2
H
5
H O / V
HCl
>
HClH
2
N
CHJ
I
1
OW
I X
CH
2
NH
2
HONO
HCl
^ C H
2
O H
48 HBr
CH
2
Br
Ho/ 'ScHjBr
CH
2
OH
H
2
O HoZ^CH
2
OH
CH
^ N/
CH,
N W
HBr
X I
AgCl CH
3
NW
HCl
XII
Vitamin B
6
is that factor of the vitamin B com
plex which prevents or cures an acrodynia-like
dermatitis in young rats.
7 - 9
If fact or 2 is add ed
to th e usua l thi ami n and riboflavin suppl ement ,
(1) Stiller, Keresztesy and Stevens,
T H I S J O U R N A L ,
61, 1237
(1939).
(2) Harris, Stiller and Folkers,
ibid.
61, 1242 (1939).
(3) Kuhn and Wendt,
Ber.
72, 305 (1939).
(4) Kuhn, Andersag, Westphal and Wendt,
ibid.
72, 309 (1939).
(5) Kuhn, Wendt and Westphal,
ibid.
72, 310 (1939).
(6) Harris and Folkers,
Science
89, 347 (1939).
(7) Gyorgy, Nature 133 498 (1934).
(8) Birch, Gyorgy and L. J. Harris,
Biochcm. J.
29, 741 (1935).
(9) Gyorgy, T H I S J O U R N A L , 60, 983 (1938).
min B
6
deficient ra ts. A compl ete rep ort of these
tests and the pharmacological properties of vita
min B
6
will be published elsewhere.
Experimental Part
3 - Cyano- 4 - ethoxymethyl - S -nitro - 6 - methyl - 2-
pyridone, V.Five grams of 3 cyano 4 ethoxymethyl 6
(10) Lepkovsky, / .
Biol. Chem.
124 125 (1938).
(11) Fouts, Helmer, Lepkovsky and Jukes,
J. Nutrition
16, 197
(1938).
(12) Birch, / . Biol. Chem. 124 775 (1938).
(13) Ke resztesy and Steve ns,
Proc. Soc. Exptl. Biol. Med.
38, 64-
65 (1938).
-
7/26/2019 Synthesis of Vitamin B6
2/3
1 24 6 S T A N T O N A . H A R R I S A N D K A R L F O L K E R S V ol. 6 1
m e t h y l - 2 - p y r i d o n e ,
2
I V, in 13 cc . of ace t ic anhyd r ide was
cooled in ice and treated with 2.2 cc. of fuming nitr ic acid
in 2 cc. of acet ic anh yd rid e with a l i t t le ure a. T he solid
gradu al ly d i ssolved as the mixtu re evolved hea t . Wh en
the tempera ture had increased to 40-45 , i t was cooled to
25 and then a l lowed to s tand unt i l no fur ther heat of re
ac t ion was not iceab le . W hen i t was poured onto ice ,
crys tal l iza t ion took place . I t was f i ltered, dissolved in
a m m o n i u m h y d r o x i d e a n d r e c r y s t a l l i z e d b y a d d i n g h y
drochlor ic ac id . T he prod uct was readi ly soluble in hot
water , a lcohol , benzene , e thyl ace ta te , d ioxane , and near ly
insoluble in e ther and pet role um ether . T he yie ld of 2-
m e t h y l - 3 - n i t r o-4-e t h o x y m e t h y l- 5- c y a n o - 2-pyr ido ne , V ,
was abou t 2 g . (32 %) . Af ter recrys ta l l iza t ion , the mel t ing
p o i n t w a s 1 6 4 - 1 6 5 .
Anal. Calcd. for C i
0
H i
1
O
4
N s: C , 50.64; H , 4 .64; N ,
17.72.
F o u n d : C ,
5 0 . 9 3 ;
H , 4 . 6 3 ; N , 1 7 .4 7 .
2 - Me thyl - 3 - nitro - 4 - ethoxymeth yl - S - cyano - 6 -
chloropyridine, VI. A mix ture of 60 g . of 3-cyano-4-
e t h o x y m e t h y l - 5 - n i t r o - 6 - m e t h y l - 2 - p y r i d o n e , V , 6 6 g . of
phos pho rus penta chlor id e ( 25 % excess) and 510 cc . of dry
chlorobenzene was heated unt i l solut ion was ef fec ted.
H e a t i n g w a s c o n t i n u e d a t s u c h a r a t e t h a t t h e p h o s p h o r u s
oxychlor ide , hydrogen chlor ide and chlorobenzene di s
t i l led off slowly from the solution at atmospheric pressure.
Af ter about one-hal f the solvent had been removed ( four
to f ive hours) , the evolut ion of hydrogen chlor ide had prac
t i ca l ly s topp ed. T he rema ining solvent was removed
under reduced pressure (10 mm.) l eaving a brown vi scous
res idue . T o th i s cooled res idue was adde d abo ut 100 cc .
of water and 20 cc . of e thanol and then the resul t ing
mixture was ext rac ted e ight or t en t imes wi th pe t roleum
e t h e r . T h i s e x t r a c t w a s c o n c e n t r a t e d o n a s t e a m - b a t h ,
f irst at atm osp her ic pressu re and finally at abou t 1 mm .
pressure , in order to remove the l as t t races of chloroben
zene which in ter feres wi th subsequent c rys ta l l i za t ion.
Th e res idue was di ssolved in abou t 50 cc . of 95 % ethan ol ,
cooled and a l i t t l e water was added s lowly to reduce the
solubi l i ty , bu t not eno ugh to cause a prec ipi ta t ion of the
prod uct as an oil . T he addi t ion of c rys ta l s as seeds was
f requent ly des i rable . Or iginal ly , th i s c rude chloropyr i -
dine der iva t ive was subl imed a t 100-125 a t
10 ~
4
m m .
t o o b t a i n t h e p u r e c r y s t a ll i n e s u b s t a n c e . T h e p r o d u c t
was recrystal l ized from alcohol.
T h e y ie l d of 2 - m e t h y l - 3 - n i t r o - 4 - e t h o x y m e t h y l - 5 - c y a n o -
6 - c h l o r o p y r id i n e , V I , w a s 2 0 g . ( 3 1 % ) ; m . p . 4 7 ^ 8 .
A b o u t 1 0 % m o r e of t h e s u b s t a n c e c a n b e o b t a i n e d f ro m
the mother l iquor .
Anal. C alcd. for C
1
O H i
0
O
3
N
3
Cl : C , 46 .9 6 ; H , 3 .91 ;
N ,
1 6 .4 6 . F o u n d : C , 4 6 . 7 9 ; H , 3 . 9 2 ; N , 1 6 . 1 8.
2- M ethyl - 3 - amino - 4 - ethoxym ethyl - S - cyano - 6-
chloropyridine, VII.
A solut ion of 25.5 g . of 2-methy l -3-
n i t r o - 4 - e t h o x y m e t h y l - 5 - c y a n o - 6 - c h l o r o p y r i d i n e , V I , i n 3 0 0
cc .
of 9 5 % alcohol was shak en in th e presen ce of 0.5 g. of
A d a m s p l a t i n u m c a t a l y s t w i t h h y d r o g e n a t a p r e s s u r e o f
t h r e e a t m o s p h e r e s . T h e h y d r o g e n a t i o n w a s s t o p p e d a f t e r
three moles of hydrogen (one-hal f hour) had been ab
sorbed and the mix ture was a llowed to cool . T he m othe r
l iquor was decanted and the crys ta l l ine compound ex
t rac te d wi th hot a lcohol . T hu s , 15 g . of pu re 2-m ethy l -3-
a m i n o - 4 - e t h o x y m e t h y l - 5 - c y a n o - 6 - c h l o r o p y r i d i n e , V I I , w a s
obta ine d. Fr om the mo ther l iquor , an addi t io nal 2 .2 g .
w a s o b t ai n e d , m a k i n g t h e t o t a l y ie l d 7 6 % ; m . p . 1 4 6 -
148.
Anal.
Calcd. for C ioH i
2
O N
3
Cl : C ,
5 3 . 2 1 ;
H , 5 .32;
N , 18.63 .
F o u n d : C ,
53. 11;
H , 5 .11 ; N , 18.48.
Dipicrate of 2 -Methyl -3- amino-4- ethoxymethyl -5-
aminomethylpyridine, VIII. A solution of 31 g. of 2-
m e t h y l - 3 - a m i n o - 4 - e t h o x y m e t h y l - 5 - c y a n o - 6 -
chloropyridine, VII, in 1400 cc. of glacial acet ic acid with
11.3 g. of sodium a ceta te , 0 .5 g . of Ad am s pla t in um cata ly s t
and 30 g . of 5% pal ladium charcoal ca ta lys t was shaken
wi th hydrogen a t a pressure of three a tmospheres unt i l
thr ee moles ha d been absorbe d. A fter f il tering from the
cata lys t , the solut ion was concent ra ted under d iminished
pressure and then taken up in a lcohol . A f ter separa t ing
f rom sodium chlor ide , the solut ion was t rea ted wi th an
alcoholic solut ion of 70 g. of picric acid. A picra te sepa
ra ted on scra tching &nd s tanding, and was recrys ta l l i zed
f rom a lcohol . I t mel ted a t 186- 187 and analyzed for a
dipicra te , y ie ld 49 g . (54.5%) .
Anal. Ca lcd. for C
28
H
23
O i
6
N
9
: C ,
40 .43 ;
H , 3 . 5 2 ; N ,
1 9 .3 0 . F o u n d : C , 4 0 . 1 9 ; H , 3 . 6 5 ; N , 1 9 . 5 5.
The Dihydrochlor ide of 2 -Methyl -3-amino-4-ethoxy-
methyl -5-aminomethylpyridine , IX. Th e dipicra te of 2-
m e t h y l - 3 - a m i n o - 4 - e t h o x y m e t h y l - 5 - a m i n o m e t h y l -
pyr idine (38.6 g . ) , VII I , was t rea ted wi th 100 cc . of hydro
chlor ic ac id (1:1) and th e l ibera ted picr ic ac id was ex t rac ted
first with ni trobenzene and final ly with ether , unti l the
e ther showed no more ye l low color . T he ac id solut ion was
concent ra ted to a th ick s i rup under d iminished pressure ,
and an equal volum e of a lcohol was adde d. T he hyd ro
chlor ide crys ta l l i zed af ter adding acetone and scra tching.
Fur ther addi t ion of ace tone caused comple te crys ta l l i za t ion
of the dihyd rochlor id e ; y ie ld 12.9 g . (81.5 %) . T he mel t
ing point was 195 af ter c rys ta l l i za t ion f rom absolute a l
cohol and acetone .
Anal.
Ca lcd. for Ci
0
H i
9
O N
3
C l
2
: C , 44.78 ; H , 7 .09;
N , 1 5 .6 7 . F o u n d : C ,
4 5 . 1 1 ;
H , 6 . 9 9 ; N , 1 5 .6 6 .
The Hydrochlor ide of 2 -Methyl -3-h ydroxy-4-ethoxy-
methyl -5-hydroxymethylpyridine , X. T h e d i h y d ro c h l o
r i d e of 2 - m e t h y l - 3 - a m i n o - 4 - e t h o x y m e t h y l - 5 - a m i n o m e t h y l -
pyridine (4 g.) , IX, was dissolved in 20 cc. of 2
TV
sulfuric
ac id and added s lowly to a hot (90 ) mixture of 2 N sul
furic acid (50 cc.) an d sodiu m nitr i te (7.5 g.) . T he re was
an immed ia te evolut ion of n i t rogen. T he l ight ye llow
solut ion was heated for an addi t ional f ive minutes , t rea ted
wi th jus t enou gh urea to decompose the excess n i t rous ac id ,
cooled and neut ra l ized to H 7 .2 wi th sodium hydroxide
solut ion , us ing brom thymol blue as an outs ide indica tor .
This s l ight ly reddish solut ion was concent ra ted under d i
minished pressure unt i l sodium sul fa te s tar ted to separa te .
At th i s point , a dark oi ly l ayer was formed which con
ta ined most of the des i red produc t . T he oi ly l ayer was
dissolved in alcohol , f i l tered from separated sodium
sul fa te , and evap ora ted to drynes s . ( In o ther experi
m e n t s t h e e n t i r e c o n c e n t r a t e d m i x t u r e w a s t r e a t e d w i t h
alcohol , e tc . ) T he res idue was then di ssolved in ace tone
an d fi ltered from separ ated sodium chlorid e. T his solu
t ion gave a strong ferric chloride test for a /3-hydroxy-
pyr idine . Dry hydroge n chlor ide was adde d to the ace tone
solut ion unt i l i t was ac id to congo pape r . A smal l amou nt
of an oi ly l ayer separa ted and the ace tone layer was de-
-
7/26/2019 Synthesis of Vitamin B6
3/3
M a y , 1 9 39
C H E L A T E C O M P O U N D S A S F L O T A T I O N R E A G E N T S
1247
can ted. A ddi t ion of a smal l am ou nt of e the r gav e a sec
ond oily l ayer which a l so was sepa ra ted . On fur ther a ddi
t ion of e ther and scra tching, c rys ta l l i za t ion commenced
and was a l lowed to proceed on s tanding in a cold room at
2-5 . T he solutio n wa s f il tered, yieldin g 1 g. of a hy dr o
chlor ide ; m. p . 110- 120 . T his was recrys ta l l i zed by di s
solving in a minimum of absolute a lcohol , adding 2-3 vol
umes of ace tone and f ina l ly e ther unt i l c rys ta l l i za t ion took
p l a c e ; m . p . 1 2 3 - 1 2 5 . T h i s h y d r o c h l o r i d e g a v e a s t r o n g
pos i t ive fer r ic chlor ide t es t s imi lar to tha t shown by
vi tamin Be.
Anal.
Ca lcd. for C
1 0
H i
6
O
3
N C l : C , 5 1 . 3 6 ; H , 6 . 8 5 ;
N ,
6 .00. F ou nd : C , 51.14; H , 7 .12; N , 6 .49.
2 - M e t h y l - 3 - h y d r o x y - 4,5- di - (brom ome thyl ) - pyr idine
H ydr obr om ide , XI .A solut ion conta in ing 0 .5 g . of the
h y d r o c h l o r i d e o f 2 - m e t h y l - 3 - h y d r o x y - 4 - e t h o x y - m e t h y l -
5 - h y d r o x y m e t h y l p y r i d i n e , X , i n 2 5 c c . of 4 8 % h y d r o -
bromic ac id was heated a t the boi l ing point for t en
min utes . O n cool ing in i ce wate r , c rys ta l s sep ara te d and
were f i l t e red , washed wi th water , ace tone and e ther ;
m . p . 2 2 3 - 2 2 4 , s h o w i n g p a r t i a l d e c o m p o s i t i o n a t 2 1 9 ;
yie ld 0 .53 g . (66%) .
T h i s c o m p o u n d a p p a r e n t l y i s i d e n t i c a l w i t h t h e o n e d e
s c r ib e d b y K u h n a n d W e n d t a s h a v i n g a m e l t i n g p o i n t of
217. T he y obta ined i t f rom the /3-methyl e ther of na tur a l
v i t a m i n B
6
b y t h e u s e o f 6 6 % h y d r o b r o m i c a c i d .
Anal. C alcd . for C
8
H i
0
O N B r
3
: C , 2 5 . 5 3 ; H , 2 . 6 6 ; N ,
3 . 7 2 . F o u n d : C , 2 5 . 9 5 , 2 5 . 9 0 ; H , 2 . 8 9 , 2 . 8 4 ; N , 3 . 7 3 .
V i t a m i n B e H y d r o c h l o r i d e o r 2 - M e t h y l - 3 - h y d r o x y - 4 , 5 -
d i - ( h y d r o x y m e t h y l ) - p y r i d i n e H y d r o c h l o r i d e , X I I . T h e 2 -
( 1 4 ) K u h n a n d W e n d t , Ber. 72, 311 (1939).
The purpose of th is paper is to present quan
tita tiv e da ta ob tained w ith a new series of flotation
reagents .
1
T he present report deals with a com
pound of known chelate structure, salicylaldox-
ime, and i ts isomers , me ta and para hydroxy-
benzaldox ime. I t is perh aps significant th at the
ortho derivative when used as a flotation reagent
recovers in commercial yields not only the copper
sulfides, but also the copper carbonates and cu
prou s oxide from a siliceous gangu e. T he only
existing re po rt on the use of oximes as flotation
reagents of which the authors are aware is that of
H o l m a n ,
2
w ho used dimethylglyoxime as a flotation
reagent for the recovery of oxidized nickel ores.
(1) Previous work by the senior auth or in th is Labor atory had
shown the ef fect iveness of cer ta in chelate compo unds including sal i -
cylaldoxim e in the separatio n of hea vy me tal minera ls from siliceous
gangue.
( 2 ) ' B . W . H o l m a n , Bull. Insl.
Wn. and Met. Nr.
314 (1930).
m e t h y l - 3 - h y d r o x y - 4 , 5 - d i - ( b r o m o m e t h y l ) - p y r i d i n e h y d r o -
b r o m i d e ( 1 . 78 g .) , X I , w a s c o n v e r t e d t o v i t a m i n B h y d r o
chlor ide by boi l ing in 150 cc . of water for twenty minutes
and removing the bromide ions wi th f reshly prepared
s i lver chlor ide . T he f il trate was eva por a ted to dryn ess ,
dissolved in 1 cc. of wate r an d 5 cc. of alcohol , f i ltered with
c h a r c o a l a n d c r y s t a ll i z e d b y a d d i n g a c e t o n e ; m . p . 2 0 6 -
2 0 8 , m i x e d m . p . w i t h n a t u r a l v i t a m i n B
3
h y d r o c h l o r i d e ,
206 -20 8 . T he yie ld was 0 .42 g. of c rys ta l s p lus 0.30 g.
of c rys ta l l ine res idu e .ma king the to ta l y ie ld abo ut 75 % .
Anal. Calcd. for
C
8
H I
2
N O
3
C I :
C , 4 6 . 7 2 ; H , 5 . 8 4 ; N ,
6.81. F o u n d : C , 4 6 . 6 4 ; H
1
5. 6 9 ; N , 6 . 7 5 .
Acknowledgments.
Th e a u th o rs wish to
th a n k Drs . M a jo r , En g e ls , S te v e n s a n d K e re sz -
tesy for helpful advice and encouragement ,
M e ss rs . H a y m a n a n d R e iss for th e m ic ro a n a ly
ses, and M essrs . S le tz inger and Wilson for tech
nical assistance.
Summary
A complete synthesis of vitamin B
6
star t ing
with e thoxyacetylacetone and cyanoacetamide
has been accomplished. T he synthetic v i tamin
B
6
hy drochloride is identical with the na tura l
vitam in B6 hydro chloride. A single dose of 100
gamma of synthetic v i tamin Be hydrochloride
gave a curative effect which paralleled that of the
natural v i tamin Be.
R A H W A Y , N . J . R E C E I V E D A P R I L 11, 1939
P r e p a r a t i o n o f O x i m e s . S a l i c y l a l d o x im e a n d t h e
m-
a n d ^ - h y d r o x y b e n z a l d o x i m e s w e r e p r e p a r e d b y t h e m e t h o d
o f B r a d y a n d D u n n .
3
T h e c r u d e s a l i c y la l d e h y d e
4
was
pur i f ied by bi sul f i t e prec ipi ta t ion , washing th i s prec ipi ta te
wi th a lcohol to remove phenol , e tc . , fo l lowed by recrys -
ta l l i za t ion f rom water , ac idi f ica t ion and s team dis t i l l a t ion ,
drying, and f ina l ly d i s t i l l a t ion a t a tmospher ic pressure .
T h e O T - a n d ^ - h y d r o x y b e n z a l d e h y d e s w e r e E a s t m a n b e s t
grad e; these were careful ly recrys ta l l i zed f rom a lcohol .
P r e p a r a t i o n of S y n t h e t i c C o p p e r O r e s . T h e c o p p e r
minera l s used were authent ic , mass ive samples of re la
t i v e l y p u r e c h a k o c i t e , c o v e l l i t e , a z u r i t e , m a l a c h i t e a n d
cupr i te proc ured f rom a rep utab le source . Th ese samp les
were examined minera logica l ly by Professor W. A. Sea
m a n a n d a n a l y z e d f o r c o p p e r c o n t e n t i n t h i s L a b o r a t o r y .
Th ese minera l s were crushed an d s ized. Th ose por t ions
which passed through a 40-mesh s ieve and were re ta ined
on a 60- mesh sieve were reserv ed for f lotat ion t est s. T he
( 3 ) B r a d y a n d D u n n , J. Chem. Soc 105, 821 (1914).
(4) Ac knowledgm ent is made to the Dow Chemical Co mpa ny
for generou s amou nts of crude salicyla ldehyd e sup plied for this work.
[ C O N T R I B U T I O N F R O M T H E D E P A R T M E N T O F C H E M I S T R Y , M I C H I G A N C O L L E G E O F M I N I N G A N D T E C H N O L O G Y]
C helate Com pounds as Flotation R eag ents. I
B Y C . C . D E W I T T A N D F R E D E R I C K VO N B A T C H E L D E R