Download 3 - hcopgnt

DETAILED STUDY OF VITAMIN
B1,B2,&B6
1
Vitamin B: (Thiamine or aneurin):
Source:
Occurs abundantly in rice and wheat. It is also found in yeast ,egg, meat,
beans, Peas,etc. in small qunatity it is also present in liver and kidney.
Isolation:
Source is extracted with acidulated water at pH
Adorption on fullers earth which adsorbs only vitamin B1.
Eluted with quinine sulphate solution.
Excess of quinine is then precipitated by Ba(OH)2 and add AgNO3
On treatment with HCl the silver salt is converted to chloride
hydrochloride of vitamin B1 which is crystalline and removed easily.
Deficiency disease:
deficiency in human causes loss of appetite, gastrointestinal disturbances,
2
muscular weakness, pain in arms and legs and decrease in blood Pressure.In
severe cases leads to Beriberi.
CONSTITUTION:
1.Molecular formula of thiamine chloride hydrochloride is C12H18N4Cl2OS
2. with sodium sulphite saturated with SO2 at room temperature cleaved
into two compounds A and B.
C12H18N4Cl2OS
+ Na2SO3
SO2
C6H9NOS + C6H9N3O3S
A
+
2NaCl
B
CONSTITUTION OF COMPOUND A;
1.The molecular formula is
C6H9NOS .
2.Compound is basic but does not react nitrous acid
the nitrogen atom is in teritiary form.
indicates that
3.It gives monochloro compound when reacted with HCl showing the
presence of one hydroxyl group .
U.V spectrum of the chloro compound is similar to that of the parent hydroxyl
compound, the later is present in side chain.
.
. 4. the unreactivity of the sulphur atom and the uv spectrum of compound A
suggested that the sulphur atom is present in a thiazole ring,
3
Confirmation: sulphur atom is lost when A is treated with alkaline plumbite
solution.
5.Oxidation of the compound A with HNO3 gives an acid ( C5H5N02S) which
was identified as 4-methyl thiazole -5-carboxylic acid II. The structure of this
has been proved by synthesis.
CH3
HO
NH
1.condensation
C
+
HC
2.hydrolysis
C
SH
Thioformamide
N
CH3
Br
S
COOH
COOC2H5
alpha-Bromo ethylacetoacetate
II
From the above points it is clear that the compoud A has the structure as II
with the only difference that one of the side chains of A has been replaced by
–COOH group in II.
6. From the above it is clear that the side chain is C2H50 which may be either
-CH2CH2OH or –CHOH.CH3 and hence the compound A III or IV.
CH3
CH3
N
N
S
III
CH2CH2OH
S
IV
CHOHCH3
4
On oxidation , either of these compounds could be converted to II. But the
compound A is optically inactive .
So, III is the structure of A because the compound IV is the structure of A
because the compound IV is optically active.
7. The structure III for A has been confirmed by synthesis , in which
thioformide is condensed with 3-chloro 5-ethoxy -2pentanone .the later
compound is synthesised from ethylacetoacetate and β-bromo diethyl ether
as shown
below
OC
CH3
BrCH2CH2OC2H5
+
OC
NaOC2H5
COOC2H5
CH
C2H5OOC
C
H2
CH2CH2OC2H5
SO2Cl2
CH3
CH3
OC
ketonic hydrolysis
Cl
OC
CH
Cl
C
CH2CH2OC2H5
Keto form
C2H5OOC
CH2CH2OC2H5
CH3
HO
C
Cl
C
enol form
CH2CH2OC2H5
3-chloro 5-ethoxy2-pentanone
5
The hydrochloride of this compound is identical with that of the product
obtained from thiamine.
It also gives acid II on oxidation with nitric acid.
Londergan have synthesised compound A 2-methyl furan.
HO
NH
CH3
1.Condensation
C
+
CH3
N
2.hydrolysis
HC
C
SH
Cl
CH2CH2OC2H5
Thioformamide
CH2CH2OH
S
compound A ( III)
Synthesis of compound A
H2-Pd/c
CH2
H2C
COCH3
HCl
CH2OH
CH3
O
-H20
CH3
N
S
CH2CH2OH
1.Cl2
2.HCSNH2
in HCOOH
O
CH3
6
Constitution of compound B:
1.The molecular formula is
C6H9N3O3S.
2. On heating with NaOH it yields sodium sulphate indicating the presence
of a sulphonic acid group in compound B .
3. The compound B was found to contain one –NH2 group as it formed
monohydroxy derivatives. Along with the evolution of nitrogen when treated
nitrous acid.
4. the compound B on heating with HCl under pressure yields ammonia and a
compound C. the U.V spectrum is very similar to that of 6-hydroxy pyrimidine.
So, the compound B is probably a 6-amino pyrimidine derivative
.
C6H9N3O3S
+
H20
HCl
1500c
C6H8N2O4S
+
NH3
7
5.Reduction of B with sodium in liquid ammonia yields 6-amino -2,5
dimethyl-pyrimidine .
This structure is confirmed by its synthesis.
O
CH3
+
H2N
H5C2OOC
HN
C.CH3
NH
ACETAMIDINE
C2H5ONa
HOHC
H3C
N
1.POCi3
formyl propionic ester
2.NH3-C2H5OH
H3C
H2N
N
N
4-Amino-2,5-dimethylpyrimidine
CH3
8
The position of sulphonic acid group:
This can be present on either side of the two methyl groups since amino group
was found to be free in compound B.
6. When thiamine is reduced with sodium in liquid ammonia. a compound D
is formed which is Identified as 6-amino 5-aminomethyl -2- methyl pyrdimidine
.proved by its synthesis.
NH2
CN
N
+
H2N
NH
CH3
C2H5O
C2H5ONa
C
C
H
H3C
N
CN
1.CH3COOH
2.H2-Pd-C
NH2
CH2NH2
N
H3C
N D
Thus in compound D, there is an amino group instead of the sulphonoic acid
9
in B is attached to the methyl group at position 5 and thus proved by its
synthesis.
NH2
NH2
NH2
CH2NH2
N
CH2Br
1.HONO
H3C
SO3
H3C
D
N
NaHSO3
2.HBr
N
Na2SO3H
N
N
H3C
N
POINT OF ATTACHMENT OF A AND B:
H3C
NH2
H2
C
Cl-
N
N+
HOH2CH2C
CH2NH2
Na/C2H5OH
N
NH3
S
ClHH2N
N
CH3
H3C
Na2SO3
NH2
CH3
N
CH2SO3H
N
+
CH2CH2OH
S
H3C
N
B
A
10
Synthesis:
structure is proved by its synthesis(williams):
NH2HBr
CH2Br
N
H3C
CH3
+
N
N
CH2CH2OH
S
NH2HBr
Br
CH2
CH3
N
N
CH2CH2OH
S
H3C
N
AgCl in CH3OH
NH2HCl
Cl
CH2
CH3
N
11
N
S
H3C
N
CH2CH2OH
thiaminechloride hydrochloride
VITAMIN B2(RIBOFLAVIN):
SOURCE: The best sources of the vitamin are yeast, green vegetables ,
liver, wheat germ, egg yolk,k milk, meat, fish etc.
Isolation:
the material is acidified with con.HCl and the vitamin is adsorbed on
fullers earth.
The adorbate is treated with basic solvents (NH3,causticsoda etc).
After several precipitations and resolutions thallium salt of vitamin is
formed.
Lactoflavin is crystallised from alcohol.
DEFICIENCY: It is necessary for growth and health
deficiency in riboflavin results in a.inflammation of the tongue, b. chelosis.
12
CONSTITUTION;
1.‘the molecular formula of riboflavin is
C17H20 N4O6.
2. Silver salt of riboflavin on acetylation gives a tetra-acetate , indicating the
presence of four hydroxyl groups.
3.Oxidation of riboflavin with lead tetra-acetate yields formaldehyde.
it indicates the presence of Primary alcoholic group.
4.There is no primary amino group since riboflavin does not react with nitrous aci
.
5.Alkaline hydrolysis of the vitamin yields urea, indicating the presence of the
fragment –NH-CO-NH. The other 2 nitrogens are teritiary.
6. Irradiation of an alkaline solution of riboflavin yields a new compound
lumniflavin or photoflavin.
Similar treatment of the vitamin in acid or neutral solution gives lumichrome.
13
7. STRUCTURE OF LUMIFLVIN:
a. Molecular formula of lumiflavin is
C13H13N4O2
b. The photolysis reaction of riboflavin to produce lumiflavin can be
represented as follows.
C17H20N4O6
hv
C13H22N4O2
C4H8O4
+
c. Lumiflavin can niether be acetylated nor oxidised by lead tetra-acetate
showing there by that
The C4 fragment is a tetrahydroxy butyl side chain.
R-CHOH-CHOH-CHOH-CH2OH
Lumiflavin was shown to contain a methyl –imine group which was not
present in riboflavin .
Therefore the methyl imino group must have replaced the missing side
chain.
e. Alkaline hydrolysis of lumiflavin yields urea and amino carboxylic acid A.
d.
C13H22N4O2
alkali
+
2H2O
C12H12N2O3
A
+
CH4N2O
urea
14
Since two molecules of water are required in the reaction, urea must come
from a ring system, and not from a side chain ureide or guanidino group
which would require only one molecule of water for hydrolysis .
the acid A easily eliminates a carbondioxide molecule to give a substance B.
This suggests that A is a β- keto carboxylic acid.
-CO2
C12H12N2O3
C11H12N2O
B
A
The compound B shows the properties of a lactam and gives one
molecule of glyoxalic acid and a compound C on boiling with NaOH solution.
C11H12N2O
NaOH
+2H2O
B
CHOCOOH
+ C9H14N2
GLYOXALIC ACID
C
Structure of the compound C:
By the usual tests, compound C was found to be an aromatic diamino
compound. Since it gave a blue precipitate with ferric chloride, it must have
N-methyl-o- phenylenediamine nucleus.
NHCH3
N-Methyl-o-phenylene diamine
NH2
.
15
The molecular formulae of the compound C (C9H14N2) and the above
mentioned nucleus (C7H10N2) shows that C2H4 should be accounted for. This
can be done by assuming the
Presence of either an ethyl group or two methyl groups in the benzene ring
But Khun showed the presence of two methyl groups by a series of
synthetic reactions and
Thus the compoud C was identified as N-methyl-4,5 diamino –o –xylene.
H3C
NHCH3
H3C
NH2
The above structure for compound C is proved by its synthesis. Therefore, the structure of the
compound B can be represented as follows which also explains the required products of
hydrolysis.
CH3
H3C
H3C
N
CO
NHCH3
NaOH
+
COOH
CHO
H3C
N
B
H3C
NH2
C
16
Since A is a beta –keto carboxylic acid of B, it can be represented as below.
CH3
CH3
H3C
H3C
N
CO
H3C
N
N
CO
-CO2
H3C
COOH
N
B
Since A and one moleculae of urea are obtaine from lumiflavin, the latter would be 6,7,9Trimethyl isoalloxazine (6,7,9 trimethyl flavin).
CH3
H3C
N
CH3
N
CO
NH
H3C
N
lumiflavin
H3C
N
alkali
CO
Ba(OH)2
H3C
N
COOH
O
+
NH2 CONH2
17
Finally the structure of the lumiflavin has been confirmed by synthesis which involves the
condensation of N-methyl -4,5-diamino-o –xylene with alloxan.the former was obtained
From o-xylene as below.
18
Structure of lumichrome:
Analytical work similar to that described for lumiflavin showed that the structure of lumichrome is I
(6,7 –dimethyl alloxazine)
Synthesis of lumichrome:
H3C
NH2
H
N
O
O
+
NH
H3C
NH2
O
O
H3C
N
H3C
N
H
N
O
NH
19
O
SIDE CHAIN OF RIBOFLAVIN:
1. The reaction mixture from which lumichrome was isolated gave positive reaction for a pentose
sugar, so the side chain is a sugar having five carbon atoms.
2. Zerewitnoff method shows that riboflavin has five active hydrogens atoms. Since one active
Hydrogen atom is present on the N3 of lumiflavin .the rest four active hydrogen atoms must
Be present in the side chain in the form of four –OH groups .must be present as a terminal
CH2OH group. Further more, riboflavin forms a diisopropylidene derivative with acetone
two 1,2 –glycolic systems must be present in the side chain (riboflavin).
The above points lead to the following structure of the side chain of riboflavin.
-CH2-CHOH-CHOH-CHOH-CH2OH
CH2(CHOH)3CH2OH
10.Thus riboflavin can be written as below.
H3C
N
N
CO
NH
H3C
N
O
Lactoflavin
The side chain contains three asymmetric carbons and hence there are 8 optically active forms
For riboflavin. The actual nature of the side chain (D- ribityl) at position 9 was proved by its
synthesis
20
Structure is proved by its synthesis:
Khun synthesis:
H3C
NH2
1. condensation
+
H3C
CHO (CHOH)3CH2OH
2. reduction
D(-) ribose
NO2
CH2(CHOH)3CH2OH
H3C
HO
NH
H
N
O
+
NH
H3C
O
NO2
O
2-amino-4,5 -dimethyl -N-D-ribityl
aniline.
alloxan
CH2(CHOH)3CH2OH
H3C
N
N
CO
NH
H3C
N
21
O
Vitamin B6 ,Pyridoxine or Adermin :
It refers to a group of three compounds namely
,pyridoxine, or adermin, pyridoxal and pyridoxamine which are
interconvertible in the form of their phosphates.
Occurrence: it is found in the plant as well as in animal eg: yeast
and fish muscle. Most abundant sources for the vitamin are yeast
and rice polishings followed by seeds and cereals.
ISOLATION:
The vitamin splits up, by heating ,from protein .
extracted with water, and acidified with dilute H2SO4
impurities are removed by silver nitrate with suitable pH .
The filterate is acidified to pH 2.
and the vitamin is absorbed on fullers earth.
The elution is carried out with Ba(OH)2 and the vitamin is precipitated by
22
any of the acids, H2SO4, phosphotungstic acid.
This precipitation is repeated for many times and lastly the vitamin is
obtained as hydrochloride. (M.P: 2090C)
Deficiency diseases:
In rats causes a specific dermatistis (acrodynia) ,inhibition of growth and
reduction in accessory reproductive organs .
In humans deficiency develops the symptoms of pellagra or anemia .
Constitution :
1.Molecular formula is
C8H11NO3.
2. Pyridoxine behaves as a weak base, and the usual tests showed the
absence of methoxyl, Methylamino and primary amino groups.
3.Zerewitnoff method showed the presence of three active hydrogen atoms.
4. With FeCl3
deep red colour
diazomethane
forms monomethyl ether indicates that one
hydroxyl group is present as phenolic.
Confirmation:
Uv spectrum of pyridoxine is quite similar with that of β- hydroxy pyridine
nucleus. Also indicates the presence of a pyridine nucleus in pyridoxine.
23
5. The mono methyl ether of pyridoxine does not give colour reaction with FeCl3
it forms diacetate with
acetic anhydride and With HBr it forms
hydrobromide of a dibromide.
Indicates : that the hydroxyl groups are alcoholic in nature.
6. Mono methyl ether of pyridoxine doesnot reacts with lead tetra acetate
indicates
the absence of two adjacent hydoxyl groups in a side chain.
7. Khun-Roth method of oxidation
CH3 group in Pyridoxine.
points out the presence of one –C-
8. MME of pyridoxine , with alkaline KMnO4
tricarboxylic acid(C9H7NO7).
gives a methoxy pyridine
The tricarboxylic acid with ferrous sulphate gives a blood colour is a
characteristic reaction to pyridine 2 carboxylic acid.
Indicates one of the three acidic groups in the tricarboxylic acid must be in the
2- position.
24
8. MME of pyridoxine with alk KMnO4
gives a molecule of CO2 and
anhydride of a Carboxylic acid.
indicates that in the parent dicarboxylic acid, the two carboxyl groups are
in the ortho positions.
Further confirmation:
The ortho dicarboxylic acid with FeSO4
does not give a red colour ,
I: it doesnot have a carboxylic group in the second position.
Therefore it follows that ,on decarboxylation, the tricarboxylic acid eliminates
the 2- carboxylic group to form the anhydride, thus the tricarboxylic acid
may have either of the following structures
COOH
COOH
HOOC
OCH3
OR
N
HOOC
OCH3
COOH
HOOC
N
Now we have that pyridoxine methyl ether has one –OCH3 and
two alcohollic groups thus the two –COOH groups in the tricarboxylic acid
could arise from the two alcoholic groups (-CH3OH) .
The third thus must have arrived from a methyl group,Thus the following 25
structures are possible for the pyridoxine and its corresponding methyl ether.
CH2OH
CH2OH
HOH2C
OH
HOH2C
OR
N
OH
CH3
H3C
N
two possible structures for pyridoxine
CH2OH
CH2OH
HOH2C
HOH2C
OCH3
OCH3
OR
N
H3C
CH3
N
Two possible structures for pyridoxine methtl ether
9. MME of pyridoxine with barium permanganate gives a dicarboxylic acid I. The dicarboxylic
acid forms anhydride with acethic anhydride and gives a florescent dye with resorcinol .
IN: the 2 –COOH groups are in o-positions to each other , moreover, the dicarboxylic
acid 1 does not give color with FeSO4 +showing that neither of the two –COOH groups is in α
-position to the nitrogen. Hence the structure of the dicarboxylic acid ,1, may be either A or B
COOH
HOOC
COOH
OCH3
HOOC
OCH3
OR
N
CH3
26
H3C
N
The position of the two –COOH groups in 1 corresponds to the
2 alcoholic groups in pyridoxine.
Khun compared these two dicarboxylic acids with that of the
synthetic compounds and found that the dicarboxylic acid obtained from
pyridoxine is A as it resembles with the synthetic Dicarboxylic acid from
4-methoxy-3-methyl isoquinoline.
CH3
COOH
N
KMnO4
CH3
OCH3
H3CO
N
HOOC
OCH3
HOOC
N
CH3
COOH
27
Hence the correct structures for 1 is A and thus pyridoxine will be 2 which explains all the
reactions.
CH2OH
HOH2C
CH2OH
OH
N
acetylation
HOH2C
CH3
PyridoxineII
OAc
N
CH3
CH2N2
CH2OAc
CH2OH
HOH2C
HOH2C
OCH3
OCH3
acetylation
N
N
CH3
CH3
Barium permanganate
HBr
COOH
HOOC
OCH3
CH2Br
BrH2C
OH
N
CH3
Dicarboxylicacid (I)
N
CH3
28
Synthesis:
structure is confirmed by synthesis , e.g., that of Harris and Folkers
CH2OC2H5
CH2OC2H5
CN
CN
C
O
CH2
CH2
C
C
Pyridine
CH3OH
H3C
NH2
H3C
O
N
H
O
ethoxy acetyl acetone
CH2OC2H5
O2N
CH2OC2H5
CN
CN
HNO3
(CH3CO)2 O
H3C
N
OH
H3C
N
OH
1.PCl5
2.H2+Pd -c
29
CH2OC2H5
CH2OC2H5
H2N
H2N
CN
CN
H2 +Pd C
H3C
H3C
N
Cl
OH
1.HNO2
2.HBr
CH2Br
CH2OH
HO
N
CH2OH
BrH2C
OH
1.H2 O
AgCl
H3C
N
H3C
N
Biological function:
these are involved in a number of important metabolic reactions of the
α –amino acids,e.g
Transamination, racemization, decarboxylation and elimination
reactions.
30
REFERENCES:
1.ORGANIC CHEMISTRY NATURAL PRODUCTS VOLUME -2---------O.P AGARWAL
2. ORGANIC CHEMISTRY NATURAL PRODUCTS VOLUME-1------------GURUDEEP CHATWAL
31
THANK
U
32