Autoxidation of resin acids. III. Photo-oxidation of abietic acid


Enoki, A.; Kitao, K.

Journal of the Japan Wood Research Society 21(2): 101-106

1975


The autoxidation of methyl abietate (I) was studied under irradiation with sun light in the air. From the reaction products five n-hexane-soluble products were isolated and identified as methyl 7-oxo-dehydroabietate (II), methyl 7 a-hydroxydehydroabietate (III), 7 a-hydroxy-8 a, 9 a; 13 a, 14 adiepoxide (IV), peroxide (V), and methyl 13 a, 14 a-epoxy-47(8)-dihydroabietate (VI) respectively. Products (II), (III), (IV) were considered to be formed through methyl 7a-hydroperoxypalustrate (X) from the analogy of the results in the nonsensitized photooxidation of methyl palustrate and methyl levopimarate. Along with hexane-soluble products, hexane-insoluble product was obtained which was probably a complex mixture having a fairly large amount of oxygen and was not further studied.

101
(Mokuzai
Gakkaishi
Vol.
21,
No.
2,
P.
101
,
-106
(1975)
(Original
article))
Autoxidation
of
Resin
Acids.
III.t
Photooxidation
of
Abietic
Acid'"
Akio
ENOKI"
and
Koichiro
KITAO"
0.'
IL
(*
3
4R)
t
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P
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o
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9a;
13a,
14a
-s;
71
-
Z*
s
,
l;
(IV),
,;•_71-„2,-
(V),
13a,
14a-
Ar!
r
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(VI)
ni
t
Lit.
L
IL
1-7tz
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Fotwialtiit
LTo)J'E(itiLo;
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)/75'-,t.
The
autoxidation
of
methyl
abietate
(I)
was
studied
under
irradiation
with
sun
light
in
the
air.
From
the
reaction
products
fi
ve
n
-hexane
-soluble
products
were
isolated
and
identified
as
methyl
7-oxo-dehydroabietate
(II),
methyl
7
a-hydroxydehydroabietate
(III),
7
a-hydroxy-8
a,
9a;
13
a,1
,
1a-
diepoxide
(IV),
peroxide
(V),
and
methyl
13
a,
14
a-epoxy-J
7
(
8
)-dihydroabietate
(VI)
respectively.
Products
(II),
(III),
(IV)
were
considered
to
be
formed
through
methyl
7a-hydroperoxypalustrate
(X)
from
the
analogy
of
the
results
in
the
nonsensitized
photooxidation
of
methyl
palustrate
and
methyl
levopimarate.
Along
with
hexane
-soluble
products,
hexane
-insoluble
product
was
obtained
which
was
probably
a
complex
mixture
having
a
fairly
large
amount
of
oxygen
and
was
not
further
studied.
1.
INTRODUCTION
In
the
preceeding
paper
we
reported
on
the
mechanism
and
products
of
the
autoxidation
of
methyl
levopimarate
and
methyl
palustrate,
both
having
homoannular
conjugate
double
bonds,
that,
in
the
nonsensitized
autoxidation,
methyl
dehydroabietate
and
transannular
peroxide
were
main
products."
Also
we
have
found
that
the
transannular
peroxides
are
further
con
-
t
Report
II:
This
Journal,
20,
600
(1974)
Received
May
9,
1974.
The
main
part
of
the
present
paper
was
presented
at
the
7th
sympo-
sium
on
The
Oxidation
Reaction
at
Nagoya
University
in
1973.
*MS
**19l
-
liff'kIW
Wood
Research
Institute,
Kyoto
University,
Uji,
Kyoto
verted
to
diepoxides
and
related
substances.
Several
investigators
have
studied
the
autoxida-
tion
of
abietic
acid
as
well
as
other
resin
acids
of
pine
gum.
However,
until
the
present,
no
clear
information
has
been
obtained
as
to
the
oxidation
products
and
the
reaction
mechanism.
S.
S.
Malevskaya
et
al.
have
reported
that
abietic
acid
takes
up
about
2
moles
of
oxygen
when
oxidized
by
air
in
benzene?
)
Harris
et
al.
proposed
the
autoxidation
mechanism
of
abietic
acid
as
in
the
following
scheme?
)
But
the
support
for
the
theory
has
not
been
satisfactorily
given
becase
no
chemically
pure
oxidation
pro-
ducts
have
been
yet
obtained.
W.
H.
Schuller
et
al.
have
reported
that
the
photosensitized
oxidation
of
abietic
acid
gives
a
diperoxide
of
which
the
structure
has
not
been
clear.')
102.
A.
Dios'
and
K.
KITAO
Mokuzai
Gakkaisla
COOS
COOH
COOH
The
purpose
of
the
present
work
is
to
in-
vestigate
the
non
-sensitized
photooxidation
products
and
the
reaction
mechanism
of
methyl
abietate.
2.
RESULTS
AND
DISCUSSION
A
solution
of
methyl
abietate
n
-hexane
was
exposed
to
sky
light
with
aeration.
The
reaction
was
followed
by
TLC.
The
reaction
mixture,
after
removing
hexane
-insoluble
precipitate,
was
concentrated
and
submitted
to
PLC,
Products
II,
III,
IV,
V
and
VI
were
obtained.
Their
structures
were
elucidated
as
follows.
The
elemental
analysis
and
mass
spectrum
of
compound
(II)
indicated
the
formula
C21F12503.
The
NMR
spectrum
of
the
compound
exhibited
absorption
corresponding
to
three
aromatic
protons
at
o
7.78
(1
H,
d,
J=2
Hz)
and
7.24
(2
H,
m)
methyl
groups
at
(ei
1.27
(3
H,
s)
and
1.21
(3
H,
s)
and
an
isopropyl
group
attached
to
an
aromatic
C
-ring
at
51.21
(6
H,
d,
J=7
Hz)
and
2.89
(1
H,
m),
The
IR
spectrum
of
the
12
20
n
H
COOS
OH
'COOS
OH
OH
compound
showed
a
new
carbonyl
function
in
addition
to
C-18
carbonyl
function.
The
UV
spectrum
of
the
compound
exhibited
the
ab-
sorption
maximum
at
254nm
(e=10800).
On
the
basis
of
the
above
data,
we
propose
the
structure
of
II
for
the
compound.
The
melting
point,
ultraviolet
absorption
maximum
and
specific
rotation
of
compound
(II)
were
identical
with
those
of
methyl
7-oxodehydroabietate
reported
by
P.
F.
Ritchie
et
al.*)
The
elemental
analysis
and
mass
spectrum
of
compound
(III)
indicated
the
formula
Culiao0i.
The
IR
spectrum
of
the
compound
showed
a
hydroxyl
function.
The
NMR
spectrum
of
the
compound
exhibited
absorption
corresponding
to
three
aromatic
protons
at
8
7.10
(1
H,
d,
J=1
Hz)
and
7.02
(2
H,
m),
a
proton
geminal
to
a
hydroxyl
group
at
5
4.56
(1 H,
m)
with
a
half
-
height
width
of
8
cps
characteristic
of
an
equatorial
proton,
an
isopropyl
group
attached
to
an
aromatic
C
-ring
at
5
1.18
(6
H,
d,
J=7
Hz)
and
2.80
(1
H,
m),
methyl
groups
at
S
1.19
16
17
14
10
H
5
4
7
I
R
IV/
038L9)
/
19
1171
(I)
(2g)
,
'R
III)
t622)91
azorphotm
precipitate
(400mg)
IVII
(19m91
`011
'OH
(IV)
11622)9)
R
(III)
(157mg)
COOCH,
Scheme
1.
Ph
otooxidation
products
of
methyl
abietate
(I)
in
n
-hexane.
Vol.
21,
No.
2,
19753
Autoxidation
of
Abietic
Acid
with
Sky
Light
103
(3
H,
s)
and
1.08
(3
H,
s).
The
ultraviolet
absorption
curve
and
specific
absorption
coef-
fi
cient
of
the
compound
was
very
similar
to
these
of
methyl
dehydroabietate.
The
above
data
suggest
that
the
compound
has
the
struc-
ture
of
III.
The
epimeric
methyl
7-hydroxy-
dehydroabietates
have
been
obtained
by
P.
F.
Ritchie
et
al.
6)
But
it
has
not
been
clear
which
is
a
-isomer
or
/9
-isomer
at
C-7
and
the
con-
fi
gurations
of
the
epimers
have
been
arbitrarily
assigned.
The
melting
point
of
compound
(III)
was
identical
with
one
of
them.
The
elemental
analysis
and
mass
spectrum
of
compound
(IV)
indicated
the
formula
C211
-
13205.
The
NMR
spectrum
of
the
compound
exhibited
absorption
corresponding
to
a
proton
geminal
to
a
hydroxyl
group,
the
presence
of
which
was
shown
from
the
IR
spectrum,
at
3
3.82
(1H,
q),
an
epoxy
proton
at
3
2.92
(1H,
s),
methyl
groups
at
3
1.07
(3
H,
s)
and
0.91
(3
H,
s),
methyl
protons
of
isopropyl
group
at
6
0.92
(3
H,
d,
J
=71.1z)
and
0.87
(3H,
d,
J=7
Hz),
a
proton
at
C-5
position
at
a
2.26
(1H,
q)
with
a
half
-height
width
of
18
cps
characteristic
of
an
axial
proton.
We
prepared
two
isomers
of
methyl
8a,
9a;
13a,
14a-diepoxy-abietan-18-oate
(VIII)
and
methyl
819,
95;1313,
145-diepoxy-abietan-18-oate
(IX)
to
compare
the
NMR
spectra
with
the
compound.'
)
The
NMR
spectrum
of
methyl
protons
of
isopropyl
function
of
the
compound
exhibited
the
same
values
of
chemical
shifts
and
coupling
constants
with
those
of
a
-isomer
of
the
isomers,
(VIII)
and
(IX).
The
half
-height
width
of
the
C-7
proton
geminal
to
the
hydroxy
group
is
9
cps,
whereas
that
of
the
C-5
axial
proton
is
18
cps.
This
suggests
the
axial
ori-
entation
of
the
secondary
hydroxyl
group.
No
characteristic
absorption
was
shown
in
the
ultra-
violet
region
of
320-220
nm.
The
above
data
enabled
us
to
propose
the
structure
of
IV
for
the
compound.
The
elemental
analysis
and
mass
spectrum
of
CH
2
c1
2
..
COOCH,
(V)
(120mg)
'excess)
fl
I
ether
COOCH
3
(I)
(600mg)
(equimolar)
compound
(V)
indicated
the
formula
Ca1Hs204.
The
NMR
spectrum
of
the
compound
exhibited
absorption
corresponding
to
two
peroxy
protons
at
6
2.98
(1H,
t)
and
2.07
(1
H,
s),
methyl
groups
at
3
1.16
(3H,
s)
and
0.80
(3H,
s),
methyl
protons
of
isopropyl
group
at
6
0.92
(3H,
d,
J=7
Hz)
and
0.90
(3H,
d,
J=7
Hz).
The
IR
spectrum
of
the
compound
exhibited
no
hydroxyl
and
carbonyl
functions
except
C-18
carbonyl
function.
The
compound
was
also
obtained
by
the
treatment
of
methyl
abietate
(I)
with
excess
m-chloroper-
benzoic
acid
in
methylene
chloride.
But
compound
(V)
could
not
be
obtained
by
the
treatment
of
methyl
13a,
14a-epoxy-/(
0
-dihydroabietate(VI)
or
methyl
135,
14/3-epoxy-SM-dihydroabietate
(VII)
with
m-chloroperbenzoic
acid.
The
UV
spectrum
of
the
compound
showed
no
charac-
teristic
absorption
curve
in
the
region
of
220-
320
nm.
The
above
data
enabled
us
to
propose
the
structure
of
V
for
the
compound
to
which
the
configurations
at
C-7,
C-8,
C-13
and
C-14
was
arbitrarily
assigned.
The
signal
appearance
of
C-14
peroxy
proton
at
such
high
fi
eld
is
due
to
the
shielding
of
the
cyclopropane
group.
If
the
compound
is
diepoxide,
such
a
high
fi
eld
signal
appearance
of
C-14
epoxy
proton
can
not
be
explained,
and
diepoxide
must
be
yielded
by
the
treatment
of
the
monoepoxides
(VI)
or
(VII)
with
m-chloroperbenzoic
acid.
The
elemental
analysis
and
mass
spectrum
of
compound
(VI)
indicated
the
formula
Call
-
1320a.
In
the
IR
spectrum,
the
compound
possessed
no
hydroxyl
function.
The
NMR
spectrum
of
the
compound
exhibited
absorption
correspond-
ing
to
a
vinyl
proton
at
d
5.73
(1H,
m),
an
epoxy
proton
at
5
2.96
(1
H,
s),
methyl
groups
at
6
1.20
(3H,
s)
and
0.80
(3H,
s),
methyl
pro-
tons
of
isopropyl
group
at
5
0.96
(3H,
d,
J=7
Hz)
and
0.91
(3H,
d,
J=7
Hz).
We
prepared
a-
and
5
-isomers
of
methyl
13,
14-eproxy-41
M-
dihydroabietate
by
the
treatment
of
methyl
abietate
(I)
with
equimolar
m-chloroperbenzoic
COOCH,
(VI)
(56mg)
s
'COOCH
3
(VI/)
(8mg)
Scheme
2.
Treatment
of
methyl
abietate
with
ra-zhloroperbenzoic
acid.
104
A.
ENOKI
and
K.
KITAO
Mok
II
z
i
Gakkaishi
LI
II)
'0011
14.
situ)
R
=
COOCH
3
„Ei
Ft
III)
;TV
'00H
Scheme
3.
acid
to
assign
the
configurations
of
compound
(VI)
at
C-13
and
C-14.
Although
the
NMR,
IR
and
mass
spectra
of
the
isomers
could
not
clarify
which
of
the
isomers
a-
or
B
-isomer,
the
major
product
of
the
isomers
may
be
a
-isomer
and
the
minor
product
of
the
isomers
may
be
B
-isomer
because
of
the
steric
requirements
of
methyl
abietate
(I)
and
the
known
predominance
of
a
-attack
on
the
C
-ring
of
the
resin
acids!
)
.
The
NMR
spectrum
and
value
of
TLC
of
compound
(VI)
were
identical
with
those
of
the
major
product
of
the
isomers
but
not
the
minor
product
of
the
isomers.
The
above
observation
suggests
that
the
structure
of
the
compound
is
VI.
The
white
amorphous
solid
which
precipitated
during
the
photooxidation
was
insoluble
in
hexane
but
easily
soluble
in
methanol.
Preli-
minary
TLC
revealed
that
it
is
neither
a
single
substance
nor
simple
mixtures.
Therefore
we
did
not
try
any
further
study.
Its
NMR
showed
very
little
absorption
in
the
region
of
5-8
ppm.
Elemental
analysis
showed
roughly
6
to
7
oxygen
atoms
per
C-21.
IR
showed
a
fairly
large
amount
of
OH
and
CO=
as
compared
to
methyl
7a-hydroxydehydroabietate
(III).
The
UV
spectrum
sugggested
the
presence
of
a
very
small
amount
of
conjugated
double
bond.
The
formation
of
epoxide
(VI)
seems
to
pro-
ceed
in
accordance
with
the
following
equation
-OR
-
DOH
,
DR
*
IR
(III)
although
we
have
obtained
little
information
on
the
reaction
mechanism
of
epoxide
(VI)
from
the
photooxidation
experiment.
C
C
1
13
1
14
+
/
ROOH
+
ROE
0
The
hydroperoxides
might
occure
during
the
process
of
the
formation
of
(II),
(III),
(IV)
and
etc.
The
formation
mechanism
and
the
configra•
tion
of
peroxide
(V)
at
C-7,
8,
13,
and
14
are
currently
under
investigation,
and
the
results
will
be
published
at
a
later
date.
We
have
disussed
in
the
preceeding
paper
that
in
the
photooxidation
without
a
sensitizer,
methyl
palustrate
and
methyl
levopimarate
have
yielded
methyl
dehydroabietate
and
diepoxides
which
have
been
formed
through
transannular
peroxides
as
the
main
products.'
)
It
is
inferred
from
the
analogy
of
the
observa-
tion
mentioned
above
that
the
formation
of
(II),
(III),
and
(IV)
might
proceed
according
as
Scheme
3.
It
seems
that
at
fi
rst
methyl
7a-hydroperoxypalustrate
(X)
occurs
as
the
intermediate
to
(II),
(III),
and
(IV)
and
the
de-
hydrogenation
and
diepoxidation
of
the
diepoxi•
dation
of
the
C
-ring
of
(X)
proceed
according
with
the
same
mechanisms
as
those
of
methyl
palustrate
in
the
sky
light
irradiation.
Vol.
21,
Vo.
2,
1975)
Autoxidation
of
Abietic
Acid
with
Sky
Light
105
3.
EXPERIMENTAL
The
NMR
spectrum
was
recorded
on
a
Hitachi
R-
22
spectrometer,
TMS
being
used
as
an
internal
stan-
dard.
The
mass
spectrometry
was
conducted
by
using
a
Shimazu-LKB
9000
gas
chromatograph-mass
spec-
trometer,
The
UV
spectrum
was
measured
by
using
a
Hitachi
-124
spectrometer.
The
IR
spectrum
and
optical
rotation
were
measured
by
using
a
JASCO
IR-
S
spectrophotometer
and
a
JASCO
DIP
-SL
automatic
polarimeter.
3.1
Abietic
acid
Abietic
acid
was
prepared
from
commercial
rosin
by
the
amine
method
of
Harris/2;
(a)n
—110°,
m
p
170-173
°
C,
A
t
E
n
n
H
nm
(e):
241(23000).
Methyl
abietate
(I)
was
prepared
by
esterification
with
diazomethane
in
ether.
3.2
Photooxidation
of
methyl
abietate
(I)
A
pyrex
fl
ask
containing
2
g
of
methyl
abietate
dis-
solved
in
800
ml
of
n
-hexane
was
placed
on
the
roof
for
sky
light
irradiation
and
aerated.
The
reaction
of
the
photooxidation
was
followed
by
stopping
the
re-
action
at
several
points
and
analysing
the
products
by
TLC
(cyclohexane:
ether
=
3
:
2
and
cyclohexane:
ether=20
:
1).
The
temperature
of
the
solution
was
kept
below
30°C
during
the
photoreaction.
3.3
Separation
of
oxidation
products
When
the
solution
was
irradiated
with
sky
light
for
60hr,
the
reaction
was
stopped.
0.8
g
of
the
amorphous
precipitate
which
was
yielded
during
the
photooxida-
tion
was
isolated
from
the
solution
by
fi
ltration.
After
the
fi
ltration,
the
solvent
was
removed
in
vacuo
and
Leg
of
the
oxidation
products
soluble
in
n
-hexane
was
gained.
The
hexane
-soluble
oxidation
product
was
submitted
to
preparative
layer
chromatography
on
Merk
Silica
gel
PF-254
with
cyclohexane-ether
(3
:2)
and
with
chloroform
-ether
-ethanol
(5
:
1
:
0.1).
Products
moved
on
the
layer
in
the
order,
(VI),
(II),
(V),
(III),
(IV).
Products
were
isolated
by
ether
elution.
Methyl
7-oxodehydroabietate
(II),
methyl
7a-hydroxy-
dehydroabietate
(III),
7
a-hydroxy-8a,9
a;
13a,
14
a-
diepoxide
(IV),
peroxide
(V),
and
methyl
13
a,
14
a-
epoxy
-
4
7
(a)-dihydroabietate
(VI)
were
obtained
in
yield
of
52,
357,
162,
338
and
19
mg
respectively.
3.4
Methyl
7-oxodehydroabietate
(II)
Recrystallization
from
aqueous
methanol
furnished
pure
(II):
mp
68-69°C;
[alr
4
+6°,
2=
1
nm
(a):
254
(
1
0800);
MS
Mje:
328
(M
.
");
NMR
(CCI4)
ii:
7.78
(1H,
d,
J=2
Hz,
C-14
aromatic
proton),
7.24
(2
H,
m,
C-11
and
C-12
aromatic
protons),
3.62
(3H,
s,
methoxy
protons),
1.27
(3H,
s,
C-19
or
C-20
methyl
protons),
1.21
(311,
s,
C-20
or
C-19
methoxy
protons),
1.21
(6H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
2.89
ppm
(1H,
m,
C-15
proton
of
isopropyl
group).
Anal.
Calcd,
for
C2rH2a0a:
C,
76.79;
H,
8.59.
Found:
C,
76.35;
11,
9.20.
3.5
Methyl
7
a-hydroxydehydroabietate
(III)
Compound
(III)
was
recrystallized
from
aqueous
methanol
in
fi
ne
needles;
mpI11-112°C;
(ajg
c1
•+15
°
;
MS
mle:
330
(Mt),
IR
idtla
cm
-1
:
3600
(-OH),
1735
(CO);
=
Amer
nm
(e):
275
(500),
266
(620),
258
(600);
NMR
(CCI4)
5:
7.10
(1
H,
d,
J=1
Hz,
C-14
aromatic
proton),
7.02
(2H,
m,
C-11
and
C-12
aromatic
protons),
4.56
(1
H,
m,
C-7
proton),
3.60
(3H,
s,
methoxy
pro-
tons),
2.80
(1
H,
m,
C-15
proton
of
isopropyl
group),
1.19
(3
H,
s,
C-19
or
C-20
methyl
protons),
1.18
(6
H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
1.08
ppm
(3
H,
s,
C-20
or
C-19
methyl
protons).
Anal.
Calcd.
for
Call
-1300a:
C,
76.32;
H,
9.15.
Found:
C,
75.89;
I-1,
9.75.
3.6
7a-Hydroxy-8a,
;
19a,
14a-diepoxide
(IV
)
Product
(IV)
could
not
be
crystallized;
MS
m/e
:
364
(M+);
IR
4
1
,
3
j,
cm
-1:
3600
(-OH),
1740
(C18-.0)
;
NMR
(CCI
4
)
3:
3.82
(1H,
q,
C-7
proton),
3.62
(3H,
s,
methoxy
protons),
2.92
(1
H,
s,
C-14
epoxy
proton),
1,07
(3
H,
s,
C-19
methyl
protons),
0.91
(3
H,
s,
C-20
methyl
protons),
0.92
(31-1,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group)
and
0.87
ppm
(3H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group).
Anal.
Calcd.
for
C21
H3203:
C,
69.20;
H,
8.85.
Found.
C,
69.80;
H,
9.05.
3.
7
Peroxide
(V)
Recrystallization
from
ether
furnished
pure(V):
mp
58,5-59.5°C;
MS
m/c:
348
(M+);
IR
v
I
M
cm
-1
:
1735
(Cisz0);
no
characteristic
absorption
in
the
ultra-
violet
region
of
220-320
nm,
NMS
(CCI4)
3:
3.60
(3H,
s,
methoxy
protons),
2.98
(1
H,
t,
Wo=4
cps,
C-7
proton),
2.07
(1
H,
s,
C-14
proton),
1.16
(3H,
s,
C-19
methyl
protons),
0.92
(3H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
0.90
(3
I-1,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
0.80
ppm
(3
H,
s,
C-20
methyl
protons).
Anal.
Calcd.
for
Call
-Isaac
C,
72.38;
H,
9.26.
Found.
C,
72.22;
H,
9.54.
3.8
Methyl
13a,14a-epoxy-4
7
(
5
)-dihydroabietate
(VI)
Recrystallization
from
ether
furnished
pure
(VI)
;
mp
58-59°C;
IR
4
B
.;
cm
-1
:
1750
(Cia=0);
no
charac-
teristic
absorption
in
the
ultraviolet
region
of
220-
320
nm;
NMR
(CC14)
3:
5.73
(1
H,
m,
C-7
vinyl
proton),
3.60(311,
s,
methoxy
protons),
2.96
(1H,
s,
C-
14
epoxy
proton),
1.20
(3
H,
s,
C-19
methyl
protons),
0.96
(3
H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
0.91
(3
H,
d,
J=7
Hz,
methyl
protons
of
iso-
propyl
group),
0.80
ppm
(3H,
s,
C-20
methyl
protons);
MS
7ri/
e:
332
(M
4
).
Anal.
Calcd.
for
C21113203:
C,
75.86;
1-1,
9.70.
Found:
C,
75.30;
H,
9.52.
3.9
Hexane
-insoluble
oxidation
products
The
amorphous
precipitate
produced
in
the
photo
-
oxidation
of
methyl
abietate
in
n
-hexane
was
isolated
by
fi
ltration
and
dried
(800
mg).
The
white
amorphous
solid
melted
at
69
to
76°C.
The
NMR
spectrum
(CCI4)
of
the
solid
showed
a
broad
peak
in
the
region
of
5.0-
6.3
ppm
(the
peak
area
in
the
region
of
5.0-6.3
ppm
:
106
A.
ENOKI
and
K.
KITAo
(Mokuzai
Gakkaithi
the
peak
area
of
methoxyl
group
at
3.6
ppm=2
:
3),
but
the
peak
disappeared
by
the
addition
of
deuterium
oxide
(D20),
and
showed
little
absorption
correspond-
ing
to
aromatic
protons
in
the
region
of
6.5-8.5
ppm.
The
IR
spectrum
showed
the
strong
absorption
of
hydroxyl
and
carbonyl
functions
in
the
3.2
and
5.8
#
regions.
The
UV
absorption
spectrum
showed
a
dis-
cernible
sohulder
at
233
nm
and
if
the
molecular
weight
is
380,
c
is
3080.
Anal.
Calcd.
for
Csi.H8306
C,
66.30;
11,
8.48
and
for
C2iI13207:
C,
63.61;
H,
8.14.
Found:
C,
64.52;
H,
8.50.
3.
10
Treatment
of
methyl
abietate
with
m-chloro-
perbenzoic
acid
3.10.1
Methyl
13a,14a-epoxy-4
7
(
8
)-dihydroabietate
and
methyl
133,
143-eposy-4
7
(
3
)-dihydroabietate:
A
solution
of
400
mg
of
m-chloroperbenzoic
acid
(85
%)
in
20
ml
of
anhydrous
ether
was
added
to
a
stirred
solution
of
600
mg
of
methyl
abietate
(I)
in
10
ml
of
andydrous
ether
by
portions
at
room
temperatures
(about
25°C).
The
mixture
was
stirred
for
an
addi-
tional
10
minutes
and
treated
with
2
%
NaOH.
The
ether
solution
was
washed
with
water,
concentrated
under
reduced
pressure
and
submitted
to
preparative
layer
chromatography
on
Merk
Silica
gel
PF-254
with
cyclohexane-ether
(2
:
1).
Then
spots
were
eluted
with
ether
to
give
56
mg
and
8
mg
of
isomers,
methyl
13,
I4
-epoxy
-P(0)
-d
ihydroabietates.
The
major
product
of
the
isomers
may
be
a
-isomer,
methyl
13a,
14a-
epoxy-4
7
(
8
O-dihydroabietate
(VI)
and
the
minor
product
of
the
isomers
may
be
t
9
-isomer,
methyl
13,8,
14A-
epoxy-if
7
(
8
)-dihydroabietate
because
of
the
steric
hin-
drance
with
C-20
methyl
group
and
the
known
predominance
of
a
-attack
on
the
C
-ring
of
the
resin
acids
e)
The
NMR
and
mass
spectra
and
the
valu'e
of
TLC
of
the
major
product
were
identical
with
those
of
compound
(VI)
obtained
in
the
photooxida-
tion
of
methyl
abietate
(I).
Methyl
13,8,
14
1
9-
epoxy-4
7
(
8
)-dihydroabietate
could
not
be
crystallized;
MS
?rile:
332
(M+);
IR
v1
1
,
3
j
cm
-
t:
1745
(CO);
=
no
characteristic
ultraviolet
absorp-
tion
in
the
region
of
220-320
nm;
NMR
(CCI
4
)
5.80
(1H,
m,
C-7
vinyl
proton),
3.60
(3
H,
s,
methoxy
proton),
2.90
(1H,
s,
C-14
epoxy
proton),
1.20
(3H,
s,
C-19
methyl
protons),
0.92
(3
H,
d,
J=7
Hz,
methyl
protons
of
isopropyl
group),
0.90
(3
H,
d,
J=7H
;
methyl
protons
of
isopropyl
group),
0.73
ppm
(3
H,
s,
C-20
methyl
protons).
The
IR
and
mass
spectra
of
the
A
-isomer
was
very
similar
to
those
of
the
a
-
isomer.
Both
of
the
isomers
did
not
change
by
the
treatment
of
them
(37
mg)
with
m-chloroperbenzoic
acid
(20
mg)
in
methylene
chloride.
3.10.2
Peroxide
(V):
A
solution
of
1.2
g
of
a-
chloroperbenzoic
acid
in
15
ml
of
methylene
chloride
was
added
all
at
once
to
a
stirred
solution
of
1
g
of
methyl
abietate
in
50
ml
of
methylene
chloride,
The
mixture
was
allowed
to
stand
for
3
hr
at
room
tem
perature
and
treated
with
2
%
NaOH.
The
ether
solution
was
washed
with
water,
concentrated
under
reduced
pressure
and
submitted
to
preparative
layer
chromatography
on
Merk
Silica
gel
PF-254
with
cyclohexan-ether
(3
:
2).
Spots
were
eluted
with
ether
to
give
200
mg
of
peroxide
(V).
The
NMR
and
mass
spectra
of
the
peroxide
were
identical
with
those
of
peroxide
(V)
obtained
by
the
photooxidation
of
methyl
abietate
(I).
REFERENCES
1)
A.
Enoki
and
K.
Kitao:
Mokuzai
Gakkaishi,
20,
342
(1974)
2)
S.
S.
Malevskaya
and
E.
V.
Kazeeva:
Zhur.
Pri-
klad.
Khim.,
21,
854
(1948)
3)
P.
W.
Sandermann:
"
Naturharze
Terpentinol
Tal-
101,"
Springer-Verlag,
Berlin
(1960)
4)
W.
H.
S
huller
,
J.
C.
Minor
and
R.
V.
Lawrence:
/
&
EC
Product
Research
and
Development,
3
(2),
100
(1964)
5)
P.
F.
Ritchie,
T.
F.
Sanderson
and
L.
F.
Mcburney
:
J.
Amer.
Chem.
Soc.,
75,
2610
(1953)
6)
J.
C.
Sircar
and
G.
S.
Fisher:
Tetrahedron
Letters,
1968,
5811.
7)
G.
C.
Harris
and
T.
F.
Sanderson:
J.
Amer.
Chem.
Soc.,
70,
334
(1948)