A study of the chemical and physical properties of epoxidized and hydrated conjugated linoleic acid

by Lam, Ngor-wai

(Uncorrected OCR) Abstract of the thesis entitled

A STUDY OF THE CHEMICAL AND PHYSICAL

PROPERTIES OF EPOXIDIZED AND HYDRATED

CONJUGATED LINOLEIC ACID

submitted by

Lam NgorWai

for the degree of Master of Philosophy

at The University of Hong Kong

in December 2002

A study was carried out on a synthetic sample of conjugated linoleic acid

[18:2(9Z,llE)] (CLA), which was prepared from ricinoleic acid (isolated from the

castor-oil plant, Ricinus cummunis). The synthesis of CLA involved the substitution

of the hydroxyl group in ricinoleic acid by bromide followed by dehydrobromination

to give the requisite CLA isomer after purification.

CBr4/ CH2CI2/ PPh3 0-5?

i) KOH / EtOH (95 %)

Br Z reflux

R1~R2 ii) BF3-MeOH / MeOH reflux

E Z ~~R2 R1""'----

(1 )

The synthetic 18:2(9Z,11E) was epoxidized usmg either m-

chloroperoxybenzoic acid, methyltrioxorhenium/hydrogen peroxide, dimethyl

dioxirane or Novozyme 43S?hydrogen peroxide to give the corresponding

monoepoxy lYiz. methyl 11,12-E-epoxy-9Z-octadecenoate ~) and methyl 9,1O-Z-

epoxy-llE-octadecenoate (4)] and diepoxy [viz. methyl 9,1O-Z;1l,12-E-

diepoxystearate (5)] CI8 derivatives.

(i)

(ii)

E Z R1~R'1

(1 )

(iii)

o 0

+ R1~R'1 + R~R'1

(5) (6)

(iv)

,0, A.

1~ ~R'1

R

(5)

(i) m-chloroperoxybenzoic acid;

(ii) methyltrioxorhenium, hydrogen peroxide; (iii) dimethyl dioxirane;

(iv) Novozyme 435? hydrogen peroxide.

Ring opening reactions of the resulting monoepoxy (3 and 4) and diepoxy (5)

derivatives in the presence of boron trifluoride etherate were conducted. Compound

3 and 4 gave a mixture of a,~-unsaturated ketones (7a!7b and 8a!8b, respectively).

The monoepoxy ~ and 4) and diepoxy (5) derivatives were treated with sodium

iodide and iodomethane in N,N-dimethylformamide to give a furanoid derivative (9),

~,y-unsaturated ketone (6 and 10) and a,~-unsaturated ketone (7a and 8a) fatty esters.

o Z 1\~2

1""'--- R

R

(3)

1 E

R~~

o

(7a)

1 E

R~R2+ n

o R1~J'~

(7a) (9)

1 E

+R~R2

o

(10)

~ R1E

R1 ~ + ~R2

R2 0

(8a) (8b)

Nal/MellDMF

o 0

R1 E ~ II + 1 _ E II + n

9 R2 R ~R2 R1~O?...R2

(6) (8a) (9)

+

Extending the study to a propargylic epoxy CI8 acetylenic fatty ester [methyl

11,12-E-epoxy-9-octadecynoate (11)], which derived from the epoxidation of methyl

IIE-octadecen-9-ynoate (Santalum album seed oil) with m-chloroperoxybenzoic acid,

was treated with boron trifluoride etherate and tetrabutylammonium

dihydrogentrifluoride led to the production of mixtures of keto-allene (l2a), keto-

acetylene (12b) and fluorohydrins (13, 14a and 14b).

2

+ ~O R

-#

R1

(12b)

OH R2

-I'ff

+ R1~ y

F

(13, threo)

OH R2 F R2

R1~ ..?,# + R1~ ? \,#

F OH

(14a, erythro) (14b, erythro)

The reaction of propargylic epoxy CI8 acetylenic Btty ester (11) with sodium

iodide and iodomethane in N,N-dimethylformamide gave mixtures of keto-allene

(12a), keto-acetylene (12b) and dihydroxy acetylene fatty esters (15).

NallMellDMF

2

o /R + 0 R2

II _ ?.p' IT #"

R1~ R1~"

(12a) (12b)

~OH ~

?

+ R1

OH (15)

Hydration of 18:2 (9Z,IIE) furnished methyl 9,12-epoxy-1O-octadecenoate

(16), a mixture of methyl 9,12-epoxy-1O-hydroxystearate (l7a) and methyl 9,12-

epoxy-ll-hydroxystearate (17b) and methyl 9,1 O-dihydroxy-llE-octadecenoate (18).

+

+

OH R1~R2 OH

(18)

The threo fluorohydrin fatty ester (13) obtained above was subjected to

chromic acid oxidation, which gave methyl ll-fluoro-12-oxo-9-octadecynoate (19).

Cyclization of compound 19 catalyzed by bis(benzonitrile )palladium(II) chloride

gave methyl 8-(4-fluoro-5-hexyl-furan-2-yl)-octanoate (20).

OH R2

~.~

R1- Y F

(13, threo)

chromic acid

PdC!:1lPhCNh

F.

'n 2

R1,JZO>-R

(20)

propylene oxide DMF

All the derivatives were rigorously characterized by a combination of

spectroscopic and spectrometric techniques. In conclusion, CLA can be readily

epoxidized and hydrated.