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CCHHAAPPTTEERR -- IIII

CHAPTER – II

SYNTHESIS OF 1-HEPTA-O-ACETYL--D-MALTOSYL-3-

SUBSTITUTED BENZOTHIAZOLYL CARBAMIDES AND N-HEPTA-O-

ACETYL-β-D-MALTOSYL-O-ALKYL CARBAMATES

ABSTRACT:

1-hepta-O-acetyl-β-D-maltosyl-3-substituted benzothiazolyl

carbamides and N-hepta-O-acetyl-β-D-maltosyl-O-alkyl carbamates have been prepared

by the interaction of Hepta-O-acetyl-β-D-maltosyl isocyanate and 2-amino

benzothiazole/substituted benzothiazoles and various alcohols respectively. These

compounds have been characterized through usual chemical transformations and IR, 1HNMR and Mass Spectral studies. The polarimetric study of the title compounds have

been carried out.

A small and simple benzothiazole nucleus is present in compounds involved

in research aimed at evaluating new products that possess interesting biological activities

such as antitumor, antimicrobial, anti-thelmintic, antileishmanial, anticonvulsant and anti-

inflammatory1. Sugar thioureas containing an N-azolyl substitutent, such as thiazolyl,

thiazoline or benzoxazole ring, have been the subject to attention in connection with the

interest in azole nucleosides analogs as antineoplastic2 and antiviral compounds

3.

Carbamides and their derivatives shows strong antibacterial activity and are

also versatile reagent in organic synthesis4.

Benzothiazoles are bicyclic ring system with multiple applications. In

1950’s a number of 2-amino benzothiazoles were intensively studied as central muscle

relaxants. After that benzothiazole derivatives have been studied extensively and found to

have diverse chemical reactivity and broad spectrum of biological activity.

Although they have been known from long ago to be biologically active5-7

their varied biological features are still of great scientific interest. Benzothiazoles show

antitumor8-10

activity, especially phenyl substituted benzothiazoles. While condensed

pyrimido benzothiazoles and benzothiazolo quinazolines exert antiviral activity11

. Bis-

substituted amidino benzothiazoles acts as potential anti-HIV agents12

. Substituted 6-nitro

and 6-amino-benzothiazoles show antimicrobial activity13

. 2-amino substituted

benzothiazoles also show anti malarial activity14

. Also Schiff base of benzothiazoles

possess antitubercular, anticancer, antitumor, antipyretic, and sterase inhibitory

activities15-16

.

During past few years, in our laboratory N-glucosylated and N-lactosylated

benzothiazolyl thiocarbamides17-18

and carbamides19

have been reported and tested for

their biological activity.

Hence it is quite interesting to synthesized carbamides having

benzothiazolyl substitutent.

Also the addition of alcohols to carbohydrate isocyanate is a general

method for the preparation of linear N-sugar, O-alkyl carbamate. This reaction is

frequently used as a tool for structure determination20

. The exhaustive literature survey

revealed that N-maltosylated benzothiazolyl carbamides and carbamates have not been

prepared earlier. Therefore, synthesis of these two types of compounds, involving the

intereaction of hepta-O-acetyl-β-D-maltosyl isocyanate (I) and 2-amino

benzothiazole/substituted benzothiazoles and alcohols have been carried out. The present

chapter deals with these syntheses.

When the interaction of hepta-O-acetyl-β-D-maltosyl isocyanate (I) and 2-

amino benzothiazole (II) have been carried out in boiling benzene medium for about 4 hr.

and the solvent benzene was distilled off, a semisolid mass was isolated, this when

triturated several times with petroleum ether (60-80°c) afforded a solid. It was

crystallized from ethanol-water, m.p. 190-192°C. The elemental analysis indicated its

molecular formula C34H41O18N3S.

Examination of the Product with m.p. 190-192°C (C34H41O18N3S)

1. Solubility:- The product was found insoluble in water and petroleum ether, while

appreciably soluble in ethanol, acetone, chloroform and benzene.

2. Action of alkaline plumbite solution:- On boiling with alkaline plumbite the

product was found non-desulphurisable.

3. Action of conc. sulphuric acid:- The presence of maltosyl group was confirmed

on the basis of its charring property when warm with conc. sulphuric acid.

4. Optical activity:- The compound was found optically active and its specific

rotation was found to be []D30

= +99.75° (c, 0.948 mol in CHCl3).

5. TLC: The purity of the product was checked by TLC and recorded Rf value 0.78

(Hexane: EtOAc, 1:1).

6. IR, 1HNMR and Mass Spectral Studies:

a) IR spectral analysis21-25

: The IR spectrum of the product distinctly showed the

bands due to υ N-H, υ C=N, υ C=O, υ C-N, and bands due to maltosyl unit.

b) 1HNMR spectral analysis

26-30: The

1HNMR spectrum of the product distinctly

shows signals due to N-H proton aromatic protons and maltosyl protons.

c) Mass spectral analysis31-38

: In its Mass spectrum the molecular ion peaks and

other important fragment peaks are tabulated in table –3(See Page No. 95)

All these facts clearly indicated that the reaction product with m.p.

190-192°C was 1-hepta-O-acetyl-β-D-maltosyl-3-(2)-benzothiazolyl carbamide

(IIIa).

When reaction of hepta-O-acetyl-β-D-maltosyl isocyanate was

extended to several other substituted benzothiazoles the corresponding 1-hepta-O-acetyl-

β-D-maltosyl-3-substituted benzothiazolyl carbamides (IIIb–IIIg) have been isolated

(Table –1).

The reaction may be stated as follows:

OAcO

AcOOOAc

OAc

O

AcOOAc

OAc

N=C=OR

N

S

H2N

OAcO

AcOOOAc

OAc

OO

AcOOAc

OAc

NH-C-NH R

N

S

(I)

Hepta-O-acetyl--D-maltosyl isocyanate

Benzene 4hr,

Reflux

(II)

Substituted bezothiazoles

(III)

1-hepta-O-acetyl--D-maltosyl -3-substituted benzothiazolyl carbamides

Where, R = a) Hydrogen, b) 4-chloro, c) 5-chloro, d) 6-chloro, e) 4-methyl,

f) 5-methyl, g) 6-methyl.

Ac = COCH3

Table 1 : Synthesis of 1-hepta-O-acetyl-β-D-maltosyl-3-substituted

benzothiazolyl carbamides (III).

Sr.

No.

Substituted

benzothiazoles (II)

1-hepta-O-acetyl-β-D-

maltosyl-3-substituted

benzothiazolyl

Yield

(%)

M.P.

(°C)

carbamides (III)

1 2-amino…. -3-(2)-benzothiazolyl …

(IIIa)

89.30 190-192

2 2-amino………….

(4-chloro…..

-3-(2)-4-chloro-

benzothiazolyl … (IIIb)

70.71 186-188

3 2-amino………….

(5-chloro…..

-3-(2)-5-chloro-

benzothiazolyl … (IIIc)

65.53 160

4 2-amino………….

(6-chloro…..

-3-(2)-6-chloro-

benzothiazolyl … (IIId)

80.36 153-154

5 2-amino………….

(4-methyl…..

-3-(2)-4-methyl-

benzothiazolyl … (IIIe)

74.60 175

6 2-amino………….

(5-methyl…..

-3-(2)-5-methyl-

benzothiazolyl … (IIIf)

62.30 183-184

7 2-amino………….

(6-methyl…..

-3-(2)-6-methyl-

benzothiazolyl … (IIIg)

69.70 170-173

Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-alkyl carbamates (v):

Hepta-O-acetyl-β-D-maltosyl isocyanate (I) was reflux with methanol (IVa)

for 3hr. On cooling and mixing with water a white granular solid was obtained. It was

crystallized from ethanol, m.p. 150°C. The elemental analysis indicated it molecular

formula as C28H39O19N.

Examination of product with m.p. 150°C (C28H39O19N):

1. It was found insoluble in water. However it was soluble in ethanol, acetone,

chloroform and benzene.

2. On warming with conc. sulphuric acid it charred.

3. The purity of the product was checked by TLC and recorded Rf Value 0.65

(Hexane: EtOAc, 1:1).

4. Its [α]D30

was found to be +60.32°C (c, 0.667 mol in CHCl3).

5. IR, 1HNMR and Mass Spectral Studies :

a) IR spectral analysis: The IR spectrum of the product clearly indicated the

presence of υ N-H, υ C=O, υ C-O and bands due to maltosyl unit.

b) 1HNMR spectral analysis: The

1HNMR spectrum of the products shows

signals due to N-H proton aliphatic protons and protons due to maltosyl

ring.

c) Mass spectral analysis: The mass spectrum of the product was also

recorded, the molecular ion peaks was also present in mass spectrum. Some

important fragment peaks were distinctly noticed.

All above facts clearly demonstrated the structure of the product with m.p.

150°C as N-hepta-O-acetyl-β-D-maltosyl-O-methyl carbamate (Va).

This reaction of hepta-O-acetyl- β -D-maltosyl isocyanate was also

extended to several other alcohols and the corresponding N-hepta-O-acetyl- β -D-

maltosyl-O-alkyl carbamates (Vb – Ve) have been isolated. (Table No. 2).

The reaction of (I) and alcohols (IV) leading to (V) may be stated as

follows.

OAcO

AcOOOAc

OAc

O

AcOOAc

OAc

N=C=O R-OH

OAcO

AcOOOAc

OAc

O

AcOOAc

OAc

NH-C-O-R

O

(I)

Hepta-O-acetyl--D-maltosyl

isocyanate

(IV)

Alcohols

(V)

1-hepa-O-acetyl--D-maltosyl

-O-alkyl carbamates

Where, R = a) methyl, b) ethyl, c) iso-propyl, d) iso-amyl, e) n-butyl.

Table 2 : N-hepta-O-acetyl- β -D-maltosyl-O-alkyl carbamates (V).

Sr.

No.

Alcohols N-hepta-O-acetyl- β -D-

maltosyl-O-alkyl carbamates

(V)

Yield

(%)

M.P.

(°C)

1 Methyl (IVa) ----O-methyl carbamate (Va) 50.18 150

2 Ethyl (IVb) ----O-ethyl carbamate (Vb) 49.21 164

3 Iso-propyl (IVc) ----O-isopropyl carbamate (Vc) 65.17 170

4 Iso-amyl (IVd) ----O-isoamyl carbamate (Vd) 62.22 175-174

5 n-butyl (IVe) ----O-n-butyl carbamate (Ve) 73.20 153-152

Experimental Part:

The required reagents used in the synthesis of benzothiazole and carbamate

derivatives were prepared as follows:

I) Preparation of Hepta-O-acetyl-β-D-maltosyl isocyanate:

It was prepared according to procedure described earlier. (See Page No. 68)

Alcohols used were of commercial grade and were purified by the

conventional methods.

II) Preparation of 2-amino benzothiazole and substituted

benzothiazoles:

These have been prepared by the oxidative cyclization of the appropriate 1-

aryl thiocarbamides with the help of molecular bromine.

a) Preparation of 1-aryl thiocarbamides39

:

These have been prepared by the interaction of ammonium thiocyanate and

appropriate aryl amine hydrochlorides. Details of typical preparation (where,

aryl=phenyl) are as follows:

Aniline (52ml) and conc. hydrochloric acid (52ml) were warmed in a

500ml of round bottom flask till its hydrochloride was formed. The hydrochloride was

dissolved in water and to this solution was added a solution of ammonium thiocyanate

(40g in 150ml water). After mixing properly the mixture was boiled over gentle bunsen

flame until the boiling solution become turbid due to sepration of phenyl thiocarbamide.

This hot solution was poured with stirring in 250ml of cold water. When 1-phenyl

thiocarbamide was obtained (40g) as a white solid. It was crystallized from boiling water,

m.p. 154°C. Melting points of other aryl thiocarbamides prepared are tabulated below.

Sr. No. 1-aryl thiocarbamides M.P. (°C) Lit. M.P. (°C)

1 1-phenyl thiocarbamide 154 154

2 1-o-tolyl thiocarbamide 160 161

3 1-m-tolyl thiocarbamide 110 111

4 1-p-tolyl thiocarbamide 189 189

5 1-o-Cl-phenyl thiocarbamide 143 143

6 1-m-Cl-phenyl thiocarbamide 140 141

7 1-p-Cl-phenyl thiocarbamide 182 183

b) Preparation of substituted benzothiazoles40-41

:

These have been prepared by oxidative cyclisation of aryl thiocarbamides

with the help of molecular bromine.

To a chloroformic paste of phenyl thiocarbamide (5g in 10ml) was added

gradually a chloroformic solution of bromine (20%) with constant stirring until a slight

excess of bromine was added as evident from an orange red colour. It was then allowed

to stand for 5-6 hrs. The resultant acidic solid (a hydrobromide) was treated with cold

ethanol, the solid, went into solution. On basification with dilute ice cold ammonium

hydroxide, 2-amino benzothiazole was separated out as a white solid (3g) m.p. 128°C.

The other substituted 2-amino benzothiazioles were prepared by the

analogous procedure. Their melting points are listed below:

Sr. No. Benzothiazole M.P. (°C)

1 2-amino benzothiazole 128

2 2-amino-(4-methyl) benzothiazole 185



5 2-amino-(4-chloro) benzothiazole 194



Interaction of 2-amino benzothiazole and hepta-O-acetyl-β-D-maltosyl isocyanate:

Formation of 1-hepta-O-acetyl-β-D-maltosyl-3-substituted benzothiazolyl

carbamides (III):

Experiment No. 1 : Synthesis of 1-hepta-O-acetyl-β-D-maltosyl-3-(2)-

benzothiazolyl carbamide (IIIa).

A benzene solution of hepta-O-acetyl- β -D-maltosyl isocyanate (0.005M,

3.3g, in 15ml) was mixed with the suspension of 2-amino benzothiazole (0.005M, 0.8g in

10ml) and mixture was reflux over boiling water bath 4 hr. After heating, benzene was

distilled off and sticky mass obtained as a residue was triturated several time with

petroleum ether to afford white solid. It was crystallized from ethanol-water, m.p. 190-

192°C. [Found: C, 50.29; H, 4.98; N, 5.14; S, 3.63, C34H41O18N3S; requires: C, 50.30, H,

5.05; N, 5.17; S, 3.94%]

The product was found soluble in ethanol, acetone, chloroform and benzene

while insoluble in water and petroleum ether. It charred when heated with conc. sulphuric

acid. It was non-desulphurisable when boiled with alkaline plumbite solution. It was

found to be optically active and its specific rotation [α]D30

= +99.75° (c, 0.978 mol in

CHCl3). The purity was checked by TLC and recorded Rf value 0.78 (Hexane: EtOAc,

1:1).

IR, 1HNMR and Mass Spectral Studies:

IR spectral analysis:

The main absorption bands observed in the IR spectrum of IIIa (fig. 1) are

listed below.

Absorption observed

(cm-1

)

Assignment Absorption expected

(cm-1

)

3350 N-H stretching 3400 – 3100 23a,24,25

1752 C = O stretching 1750 – 1735 23b, 26

1537 C=N stretching 1689 – 1771 23e

1374 C- N stretching 1350 – 1280 30b

1233 C-O stretching 1210 – 1163 31

1039 & 900 Characteristic of maltose 1100-1000 & 910-90027

769 C-S stretching 800 – 600 26

1H NMR spectral analysis:

The 1HNMR spectrum of IIIa (fig. 2) distinctly displayed signals due to

aromatic protons at δ 7.69 – 7.27 ppm31

, N-H protons at δ 6.30 – 6.21 ppm31

, signals due

to maltosyl protons at δ 5.64 – 3-76. ppm27-28

and acetyl protons at δ 2.23 – 1.90 ppm.32-35

Mass spectral analysis:

The mass spectrum23-37, 38

of IIIa (fig. 3) also recorded. It displayed the

molecular ion peak. Other important fragment peaks with m/z value are tabulated in table

3.

Table 3 : Mass spectral data of IIIa.

Sr.No. Ion m/z

1 M 881

2 [M-C8H6N3SO) = HAM+ 619

3 [HAM – AcOH] 559

4 [TAG – AcOH] 271

5 [TAG – 2AcOH, CH2CO] 169

6 [C6H5O2] 109

Where,

HAM = Hepta-O-acetyl--D-maltosyl.

TAG = Tetra-O-acetyl--D-glucosyl.

Experiment No. 2 : Synthesis of 1-hepta-O-acetyl- β -D-maltosyl-3-(2)-4-chloro

benzothiazolyl carbamide (IIIb).

A hepta-O-acetyl- β -D-maltosyl isocyanate (0.005M, 3.3g) and 2-amino-4-

chloro benzothiazole (0.005M, 1.09g) in 30 ml benzene was refluxed over boiling water

bath for 4 hr. Benzene was removed by distillation and sticky mass obtained as residue

was triturated several times with petroleum ether a white product separated out. It was

crystallized from ethanol-water, m.p. 186-188°C. [Found: C, 47.26; H, 5.20; N, 4.98; S,

3.84, C34H40O18N3SCl; requires: C, 47.28; H, 5.21; N, 5.09; S, 3.87%]

The product when heated with conc. sulphuric acid charring was observed.

It was found non-desulphurisable when boiled with an alkaline plumbite solution. The

specific rotation [α]D30

= +45.32° (c, 0.987 mol in CHCl3). TLC of the product shows Rf

value 0.90 (Hexane: EtOAc, 1:1). The product was found soluble in ethanol, acetone,

chloroform and benzene while insoluble in water and petroleum ether.



The main absorption bands observed in IR spectrum of IIIb (Fig. 4) have

been assigned as follows:

Absorption observed

(cm-1

)


(cm-1

)

3471 N – H stretching 3400 – 3100 23a,24,25

1751 C = O stretching 1750 – 1735 23a,

26

1599 C = N stretching 1689 – 1471 23e

1376 C – N stretching 1350 – 1280 30b

1237 C – O stretching 1210 – 1163 31

1041 & 942 Characteristic of maltose 1100-1000 & 910-900 27

769 C – S stretching 800 – 600 26


The 1HNMR spectrum of IIIb (fig. 5) distinctly displayed signals due to

aromatic protons at δ 7.49 – 7.2631

, N-H proton at δ 6.25 ppm, maltosyl protons at δ 5.62

– 3.74 ppm27-28

and acetyl protons at δ 2.25 – 2.02 ppm32-35.


The mass spectrum23, 37, 38

of IIIb (fig. 6) were also recorded. molecular ion

peak as well as other important fragments with m/z value are tabulate in table – 4.

Table 4 : Mass spectral data of IIIb

Sr.No. Ion m/z

1 M 845

2 [M+ – 2AcOH] 725

3 [M+ -C8H6N3SO] = HAM

+ 619

4 [HAM – AcOH] 559

5 [HAM – C12H16O8] = TAG+ 331


7 [C6H5O2] 109

Where,



Experiment No. 3 : Synthesis of 1-hepta-O-acetyl-β-D-maltosyl-3-(2)-5-chloro

benzothiazolyl carbamide (IIIc).

Hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) and 2-amino-5-

chloro benzothiazole (0.005M, 1.09g) in 20ml benzene was refluxed over boiling water

bath for 4 hr. Benzene was removed by distillation and sticky mass obtained as residue

was triturated several times with petroleum ether while product separated out. It was

crystallized from ethanol-water, m.p. 160°C. [Found: C, 47.26; H, 5.19; N, 5.08; S, 3.85,

C34H40O18N3SCl; requires: C, 47.28; H, 5.21; N, 5.09; S, 3.87%]

The product when heated with conc. sulphuric acid charring was observed.

It was found non-desulphurisable when boiled with alkaline plumbite solution. The

specific rotation [α]D30

= +54.40° (c, 0.990 mol in CHCl3). TLC of the product shows Rf



Experiment No. 4 : Synthesis of 1-hepta-O-acetyl- β -D-maltosyl-3-(2)-6-chloro

benzothiazolyl carbamide (IIId).

A benzene solution of hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M,

3.3g in 25ml) and benzene solution of 2-amino-6-chloro benzothiazole (0.005M, 1.09g in

5ml) was mixed and reaction mixture was refluxed over boiling water bath for 4 hr.

Benzene was distilled off and sticky mass obtained as residue was triturated 3 to 4 times

with petroleum ether to afford, a white product. It was crystallized from ethanol-water,

m.p. 153-154°C. [Found: C, 47.26; H, 5.20; N, 5.10; S, 3.85, C34H40O18N3SCl; requires:

C, 47.28; H, 5.21; N, 5.09; S, 3.87%]

The product was found non-desulphurisable when boiled with alkaline

plumbite solution. It charred when warm with conc. sulphuric acid, its specific rotation

[α]D30

= +65.70° (c, 0.993 mol in CHCl3). TLC of the product shows Rf value 0.87

(Hexane: EtOAc, 1:2). The product was found soluble in ethanol, acetone, chloroform

and benzene while insoluble in water and petroleum ether.

Experiment No. 5 : Synthesis of 1-hepta-O-acetyl- β -D-maltosyl-3-(2)-4-methyl

benzothiazolyl carbamide (IIIe).

A benzene suspension of 2-amino-4-methyl benzothiazole (0.005M, 0.82g)

was added to benzene solution of hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g)

and the reaction mixture was refluxed over boiling water bath for 4 hr. Benzene was

removed by distillation and sticky mass obtained as a residue was triturated with

petroleum ether 3 to 4 times. Finally a white product separated out. It was crystallized

from ethanol-water, m.p. 175°C. [Found: C, 50.86; H, 5.20; N, 5.11; S, 3.84,

C35H43O18N3S; requires: C, 50.90; H, 5.21; N, 5.09; S, 3.87%]

The product charred when heated with conc. sulphuric acid. On boiling

with alkaline plumbite solution, it was found non-desulphurisable. Its specific rotation

[α]D30

= +123.20° (c, 0.991 mol in CHCl3). TLC of the product carried out and recorded

of Rf value 0.79 (Hexane: EtOAc, 1:1). The product was found soluble in ethanol,

acetone, chloroform and benzene while insoluble in water and petroleum ether.

Experiment No. 6 : Synthesis of 1-hepta-O-acetyl- β -D-maltosyl-3-(2)-5-methyl

benzothiazolyl carbamide (IIIf).

2-amino-5-methyl benzothiazole (0.005M, 0.82g) was added to benzene

solution of hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) in 20ml benzene and

reaction was carried out over boiling water bath for 4 hr. Benzene was distilled off and

sticky residue obtained. This on trituration with petroleum ether, a white product was

separated out. It was crystallized from ethanol-water, m.p. 183.184°C. [Found: C, 50.89;

H, 5.20; N, 5.08; S, 3.86, C35H43O18N3S; requires: C, 50.90; H, 5.21; N, 5.09; S, 3.87%]

The product was found non-disulphurisable when boiled with alkaline

plumbite solution. It charred when warm with conc. sulphuric acid. Its [α]D30

was found

to be +141.51° (c, 0.982 mol in CHCl3). The purity was checked by TLC and recorded

Rf value 0.78 (Hexane: EtOAc, 1:1). The product was found soluble in ethanol, acetone,


Experiment No. 7 : Synthesis of 1-hepta-O-acetyl- β -D-glucosyl-3-(2)-6-methyl

benzothiazolyl carbamide (IIIg).

The reaction of hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g in

15ml benzene) and 2-amino-6-methyl benzothiazole (0.005M, 0.82g in 5ml benzene) was

carried out over boiling water bath for 4 hr. Benzene was removed by distillation and the

sticky mass obtain as a residue was triturated with petroleum ether 3 to 4 times. Finally a

white product separated out. It was crystallized from ethanol- water, m.p. 171-173°C.

[Found: C, 50.89; H, 5.20; N, 5.10; S, 3.86, C35H43O18N3S; requires: C, 50.90; H, 5.21;

N, 5.09; S, 3.87%]

The product found non-desulphurisable, when boiled with an alkaline

plumbite solution. It charred on heating with conc. sulphuric acid. Its [α]D30

was found to

be -296.43° (c, 0.933 mol in CHCl3). The purity was checked by TLC and recorded Rf





IR spectrum of IIIg (Fig. 7) exhibited the presence of following bands.

Absorption observed

(cm-1

)


(cm-1

)

3487 N-H stretching 3400 – 3100 23a, 24, 25

1749 C = O stretching 1750 – 1735 23b – 26

1634 C = N stretching 1689 – 1471 23e

1375 C – N stretching 1350 – 1280 30b

1238 C – O stretching 1210 – 1163 31


774 C – S stretching 800 – 600 26


The 1HNMR spectrum of IIIg (fig. 8) displayed the signals due to N-H

proton δ 5.62 ppm, aromatic proton at δ 7.36–7.26 ppm31

. Methyl protons at δ 2.37

ppm32

, maltosyl protons at δ 5.59–3.97 ppm27-28

and acetyl protons at 2.23–2.03 ppm32-36

.


The Mass spectrum of IIIg (fig. 9) was also recorded. The molecular ion

peak as well as other important fragment peaks with m/z value listed in table – 5.

Table 5 : Mass spectral data of IIIg

Sr.No. Ion m/z

1 M 825

2 [M+ – 2AcOH] 705

3 [M+ -C8H6N3SO] = HAM

+ 619

4 [HAM – AcOH] 559

5 [HAM – C12H16O8] = TAG+ 331


Where,

HAM = Hepta-O-acetyl--D-maltosyl

TAG = Tetra-O-acetyl--D-glucosyl

Interaction of Hepta-O-acetyl-β-D-maltosyl isocyanate and various Alcohols:

Formation of N-hepta-O-acetyl-β-D-maltosyl-O-alkyl carbamates (V):

Experiment No. 1 : Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-methyl

carbamate (Va).

Hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) was added to

methyl alcohol (20ml) and the reaction mixture was refluxed over boiling water bath for

3 hr. It was then allowed to cool and pour it in water with vigorous stirring, a white

granular solid was separated out. It was crystallized from aqueous ethnaol, m.p. 150°C.

[Found: C, 48.37; H, 5.59; N, 1.98; C28H39O19N; requires: C, 48.48; H, 5.62; N, 2.02%]

It was found soluble in alcohols, acetone, chloroform and benzene while

insoluble in water and petroleum ether. It charred when warmed with conc. sulphuric

acid. The specific rotation was found to be [α]D30

= +60.32° (c, 0.667 mol in CHCl3). The

purity was checked by TLC, and recorded Rf value 0.65 (Hexane: EtOAc, 1:2).



The main absorption bands observed in the IR spectrum of Va (Fig. 10) are listed below:

Absorption observed

(cm-1

)


(cm-1

)

3492 N – H stretching 3400 – 3100 25a, 31

1750 C = O stretching 1750 – 1735 23d, 31

1375 C – N stretching 1350 – 1280 23e

1237 C – O stretching 1210 – 1163 30b



The 1HNMR spectrum of Va (Fig. 11) distinctly displayed signals due to N-

H proton at δ 7.26 ppm30


, acetyl protons at δ

2.15–2.00 ppm30-35

and methyl protons at δ 1.57 ppm32-35

.


The mass spectrum of Va (Fig. 12) was also recorded M+ as well as other

important peaks with m/z value are tabulated in table 6.

Table 6 : Mass spectral data of Va.

Sr.No. Ion m/z

1 M 693

2 [M+ - C2H4O2 N]= HAM

+ 619

3 [HAM – AcOH] 559

3 [HAM – C12H16O8 ] = TAG 331

3 [TAG – 2AcOH] 211


5 [C6H5O2] +

109

Where,



Experiment No. 2 : Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-ethyl carbamate

(Vb).

Hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) was mixed with

ethyl alcohol (20ml) and the reaction mixture was reflux over boiling water bath for 3 hr.

After heating the reaction mixture was allowed to cool and pour it in ice cold water, a

granular white solid was isolated. It was crystallized from aqueous ethanol, m.p. 164°C.

[Found: C, 49.20; H, 5.75; N, 1.97, C29H41O19N; requires: C, 49.22; H, 5.79; N, 1.98%]

The product charred when heated with conc. sulphuric acid. Its [α]D30

= -

40.50° (c, 0.667 mol in CHCl3). The purity of product was checked by TLC and recorded

Rf value 0.63 (Hexane: EtOAc, 1:1).

Experiment No. 3 : Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-isoporpyl

carbamate (Vc).

Hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) was mixed with

isopropyl alcohol (20ml) and the reaction was carried out over boiling water bath for 3 hr.

After heating the reaction mixture was allowed to cool. It was then pour into ice cold

water with stirring a granular white solid was separated out. It was crystallized from

aqueous ethanol, m.p. 170° C. [Found: C, 49.89; H, 5.93; N, 1.95, C30H43O19N; requires:

C, 49.93; H, 5.96; N, 1.94%]

It was found soluble in ethanol, acetone, chloroform and benzene while

insoluble in water and petroleum ether. It charred when warmed with conc. sulphric acid.

The product was optically active and its specific rotation was found to be [α]D30

= -70.35°

(c, 0.668 mol in CHCl3). The purity of product checked by TLC and recorded Rf value

0.71 (Hexane: EtOAc, 1:1).

Experiment No. 4 : Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-isoamyl

carbamate (Vd).

Hepta-O-acetyl-β-D-maltosyl isocyanate (0.005M, 3.3g) was added to

isoamyl alcohol and the reaction was carried out at 130-150°C. Afterwards, reaction

mixture was allowed to cool and pour in ice cold water, a granular solid separated out. It

was crystallized from ethanol-water, m.p. 174-175°C. [Found: C, 50.96; H, 6.21; N, 1.90;

for C32H47O19N; requires: C, 51.26; H, 6.27; N, 1.86%]

The product was soluble in ethanol, acetone, chloroform and benzene while

insoluble in water and petroleum ether. It charred when heated with conc. sulphuric acid.

The product was optically active and its specific rotation was found to be [α]D30

=

+104.13° (c, 0.674 mol in CHCl3). The purity of the product checked by TLC and

recorded Rf value 0.77 (Hexane: EtOAc, 1:1).

Experiment No. 5 : Synthesis of N-hepta-O-acetyl-β-D-maltosyl-O-n-butyl

carbamate (Ve).

n-Butyl alcohol (20ml) was mixed with hepta-O-acetyl-β-D-maltosyl

isocyanate (0.005M, 3.3g) and reaction was carried out at 120-150°C. Afterwards, the

reaction mixture was allowed to cool and pour into ice cold water, a granular solid

separated out. It was crystallized from aqueous ethanol, m.p. 152-153°C. [Found: C,

50.59; H, 6.09; N, 1.89; C31H45O19N; requires: C, 50.61; H, 6.12; N, 1.90%]

The product was soluble in ethanol, acetone, chloroform and benzene while

insoluble in water and petroleum ether. It charred when heated with sulphuric acid. The

product was optically active and its [α]D30

= +64.62° (c, 0.667 mol in CHCl3). The purity

of the product checked by TLC and recorded Rf value 0.80 (Hexane: EtOAc, 1:1)



The main absorption bands observed in the IR spectrum of Ve (Fig. 13) are

listed below:

Absorption observed

(cm-1

)


(cm-1

)

3483 N – H stretching 3400 – 3100 25a, 31

1745 C = O stretching 1750 – 1735 23d, 31

1367 C – N stretching 1350 – 1280 23e

1242 C – O stretching 1210 – 1163 30b



The 1HNMR spectrum of Ve (Fig. 14) distinctly displayed signals due to N-

H proton at δ 7.23 ppm31


and acetyl protons at δ

2.10–1.92 ppm31-35

.


The mass spectrum of Ve (Fig. 15) was also recorded molecular ion as well

as other important peaks with m/z value are tabulated in table 6.

Table 6 : Mass spectral data of Ve.

Sr.No. Ion m/z

1 M 735

2 [M+ - C2H4O2 N]= HAM

+ 619

3 [HAM – AcOH] 559

3 [HAM – C12H16O8 ] = TAG 331

3 [TAG – 2AcOH] 211


5 [C6H5O2] +

109

Where,

HAM = Hepta-O-acetyl--D-maltosyl

TAG = Tetra-O-acetyl--D-glucosyl

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