Application of 2d-nmr spectroscopy in the structural determination of a new tobacco cembranoid

Tetrahedron Printed

Letters,Vol.25,No.l2,op Great Britain

in

APPLICATION

1299-1302,1984

OF ZD-NMR

SPECTROSCOPY

IN THE STRUCTURAL

A NEW TOBACCO

Toshiaki

Research

Abstract.

Nishida,

Inger

Department,

Wahlberg,

Swedish

Recent

studies a wide

have

array

shown

that

the

of diterpenoids

Nordfors,

Company,

cuticular

Carmen

P.O.

amount.

These

cembranoids

cembranoid

dials

the

isolation

(2, -- 3) being

(11, which

and structure

is a plausible

Vogt and Curt

Box 17007,

S-104

The new compound from

by flash

An analysis

and flower

components

using from

of most

R. Enzell

tobacco -

and present

2D-NMR

spectroscopy,

the 42,6R-diol

2.2

@_(

Sweden.

the structure

varieties

and (lS,2E,4R,6R, in a substantial

flowers

of Greek

chromatography

3

data

atoms

over showed

are

was obtained

tobacco4

in a 2.1 mg yield

by HPLC

silica that

at 1665 and 1625 cm -l; two oxygen

-

of a new tobacco

-

2

(11, C20H3203,

of its spectral

[IR bands

The remaining

.OO Ltd.

OF

62 Stockholm,

the (1&2E,4~,6~,7E,llE)-

the major

derived

1

followed

leaf

class,

determination,

metabolite

7$X${

(83 g) derived

+

(2, to give rise to the majority of the other tobacco -- 3) have been postulated by biotransformations such as oxidations, acid-induced rearrangements and dehydrations.

We now report

two

wax of the

of the cembrane

7E,llE)-2,7,11-cembratriene-4,6-dials

group

DETERMINATION

Proton-proton shift correlated ZD-NMR spectroscopy has been used to determine of a new tobacco cembranoid as (1~,2E,4~,6~,7E)-4,6-dihydroxy-2,7,12(20)-cembratrien-l1one (1). has been veriEed by ch;mical means. _ This assignment

contains

$3.00 Press

CEMERANOIDl

Kerstin

Tobacco

0040-4039/84 81984 Peryamon

using

gel and HPLC 1 contains

signals

accommodated

at 6

a column

5.69 and 6.00 by a secondary

fraction

packed

on Spherisorb

an 0x0 group

1299

from

and Spherisorb

with

an exocyclic

‘H NMR spectrum

and a tertiary

extract

PrepPak-500/C18

5 Nitrile

conjugated in the

C (6.2 g) of
with

hydroxyl

5 columns. methylene

(CDC13)]. group

1300

I

sa,Ha

\

Hbss H-19

H-7

Table

H-16 H-l7

1 H-lOb

H-6

$2

9.7 Hz

=

-31,14a

=

21,14b

=

$15

= =

J2,3 -?5a,5b &a,6 &b,6 36,7 -37,19 29a,9b J9a,lOa <9a,lOb

6.7 Hz 15.9Hz Hz

1.3 Hz

=

7.1 Hz

= =

9.3 Hz

=

1.3 Hz

= -14.4

=

Hz

10.0 Hz 4.1 Hz 4.2 Hz

29b,lOa

=

29b,lOb JIOa,lob

7.1 Hz = = -14.6 Hz

J13a,13b

= -17.2

J13a,14a

=

?13a,l4b

=

lom5 Hz

?13b,14a

=

loa

%3b,14b

JJk

4.0 Hz

= -14.4

=

I

9.6 Hz

Hz

6.6 Hz

Hz

3.9 Hz

= = -14.0

Hz

-?14a,14b 315,16

=

6.7 Hz

515,17

=

6.7 Hz

JZOa,ZOb

=

1.7 Hz

Fig.

la.

300 MHz

Fig.

lb.

Contour

‘H

is composed period,

NMR

plot of the

tl,

echo”shaping

spectrum

of 1 run in C6D6. ‘H - ‘H shift correlation (Jeener)

of 512 x 512 data was incremented function”

point

spectra,

in 256 steps. 7

was used

each

The mixing

in both

time

spectrum

consisting pulse

dimensions.

of 1 run in C6D6. The map of 96 transients. The evolution

was reduced

to 45’

and a pseudo-

1301

[OH-absorption presence that

of two additional

C NMR signals

double

bonds,

_1 is carbomonocyclic. The occurrence of an isopropyl

group

cm-‘)

and two methyl

group

and the other

diterpenoid

groups, being

of the

Proton-proton the

13

in the IR spectrum;

Jeener-spectrum

couplings

which

of appropriate spectrum the

H-l

were

in Fig.

peaks

bonds

are

to form

carbon

atom

and the demonstrated

; IR bands at 1384 and 1369

carrying

1.21 and 1.691, reinforced

at - 6

between

delineated H-l

the correlation

and the

spectrum. (Table

fragments these

was used to confirm

two protons

due to low intensities

The coupling

not conjugated,

spectroscopy

1 (C6D6)

in the CDC13

of structural

group

ZD-NMR

and H-15,

was undertaken.

formulation

signals

results

and one is trisubstituted,

at - 6 0.85 and 0.92 to the

These

the tertiary our view

that

hydroxyl _1 is a

class.

not ascertained

cross

doublets

one is attached

(methyl

correlated shown

between

at C-20,

vinylic

67.9 (d) and 73.5 (s)].

one is disubstituted

(methyl

of which

cembrane shift

of which

at 6

the

can only be combined

at C-14

shift

-via the

a 4,6-dihydroxy-2,7,12(20)-cembratrien-11-one

all protons

being

results

carbon

in 1; the

the two protons

revealed

an analysis

information

1,2-disubstituted

576 Thus,

assignment.

and between

peaks,

the aid of these

1) and chemical

A and B. Since

of almost

of the cross

With

this

thus

by the presence of the lD-

obtained

and trisubstituted

atom

carrying

allowed double

the tertiary

hydroxyl

structure.

H? H-#CH2~ C-CH3 Y

A

B

H%

The present cembranoid ZD-NMR _1 where region

study,

have

in which

the

spectroscopy coupled

over

protons

chemical

traditional

have

shifts

for the

been determined

small

first

decoupling chemical

and coupling

time,

constants

illustrates

the

experiments.

shift

differences,

of ail protons

advantage

This is particularly e. g. those --

in a tobacco

of homoscalar-correlated true

resonating

for cases

like

in the methylene

of the spectrum.

With the gross

of -1 at hand, llS)-2,7,12(20)-cembratriene-4,6,11-trio1 assigned concluded

to C-2 that

structure

to C-8

a comparison (4)’ proved -

for -1 were close 1 has a 2E,42,6R,7E-stereochemistry.

This assignment

and C-18

was readily

cembratriene-4,6-dial 2,7,12(20)-cembratrien-11-one,

(519 with -

by treatment

CuC12

in chloroform. is formed

fruitful.

to those

verified

which

of the

13

C NMR spectra

Thus,

since

the

of the corresponding

of -1 and (lS,ZE,42,6R,7E, chemical signals

shifts

of the signals

for ft, it was

of (lS,2E,4S,65,7E,llS)-11-hydroperoxy-2,7,12(20)lo The major

by dehydration,

product,

proved

(1). _ This route

(12,2E,45,6R,7E)-4,6-dihydroxy-

to be identical

to the new tobacco

isolate

to -1 may resemble that occurring in tobacco, a conclusion supported by the fact that the 11%hydroperoxide 5, which is a plausible metabolite of the 4S,6R-diol 1, has recently been isolated from _ tobacco (Scheme 1). An alternative route to 1 would involve regioselective oxidation of the 45,6R,llSand/or

42,6R,llR-trio1 -

(4, 6) both of which

are tobacco

constituents.

478

1302

Scheme

Acknowledgements. Morris,

University

References 1.

Part

of Manchester,

2

1. Wahlberg

3.

1 was a gum,

Tobacco

and C.R. which

and for valuable

2

Tabakforsch., (c 0.15,

University,

and to Dr. G.A.

advice.

in press.

CHC13);

0.85

: 320

277 (1, C17Hz503),

and C4H50),

(M,

at 3602,

3480,

3090,

0.21, 302 (2, C20H3002),

95 (31, C7H11

and C3H30)

and 43 (100,

(d, 3 = 6.8 Hz) (H-16/H-17),

1665, 287 (1,

259 (41, 241 (2), 231 (3, C16Hz30),

and C7HqO),

55 (33, C4H7

(d, J = 6.8 Hz)/0.92

bands

IR (CHC13)

[m/z?%, composition)] --

MS

137 (131, 121 (181, 109 (20, C8H13

69 (29, C5H9

(CDC13):

Be&age

[a] D -16’

284 (0.8, Cz0Hz80),

(4, C14Hz20),

-14.6

of software

Oxford

Chemistry.

Enzell, had

1384 and 1369 cm -l;

C19Hz702),

C6H9),

for gifts

to Dr. R. Freeman,

and notes

61 in the series

1625,

We are grateful

1.

206

and C6H70),

C2H30

1.21 (s, H-181,

81 (28,

and C3H7);

‘H NMR

1.65 (dd, 2 = 1.3 and

Hz, H-5a),

1.69 (d, -J = 1.5 Hz, H-191, 2.18 (dd, J = 7.1 and -14.6 Hz, H-5b), 4.66 (ddd, 3 = 1.3, 7.1 and 9.4 Hz, H-61, 5.50 (dq, -J = 1.5 and 9.4 Hz, H-7), 5.4-5.6 (overlapping signals, H-2 and H-31, 5.69 (t, J = 1.6 Hz, H-20a)

(C-2), lo),

139.1 203.4

(C-181,

(C-31,

(C-11),

16.0 (C-19)

4.

I. Wahlberg,

5.

A. Bax,

147.3

R. Arndt,

R. Freeman

A. Bax and R. Freeman,

7.

A. Bax,

I. Wahlberg, (1982)

35.0 (C-131,

I. Wallin,

C. Vogt,

Morris,

J. Magn.

and G.A.

67.9 (C-61, 27.0

13C NMR (CDCI

128.4

(C-141,

(C-71,

137.7

32.4 (C-151,

): 6 46.0

(C-83,, 28.5

19.5/20.9

(C-l),

(C-91,

128.4

36.8 (C-

(C-16/C-17),

31.4

(C-20).

I. Forsblom, and G.A.

R. Freeman

45.3 (C-5;,

(C-121,

and 122.3

6.

8.

and 6.00 (d, J = 0.9 Hz, H-20b);

73.5 (C-41,

Reson.

Morris,

C. Narbonne,

T. Nishida

J. Magn.

44 (1981)

J. Magn. T. Nishida,

and C.R.

Reson.

Enzell,

42 (1981)

164.

43 (1981)

333.

Acta

Chem.

Stand.,

in press.

542.

Reson. C.R.

Enzell

and J.-E.

Berg,

Acta

Chem.

Stand.,

836

147.

9.

I. Wahlberg,

10.

To 10 mg of 5 in 3 ml of chloroform was added 5 mg of CuC12x2H20. The reaction mixture was stirred at room temperature for 24 h, washed with water, dried and concentrated. The residue was separated by HPLC (Received

K. Nordfors,

(Spherisorb in

C. Vogt,

5 Nitrile, UK 21

T. Nishida

hexane/ethyl

December

1983)

and C.R.

acetate

Enzell,

40:60)

Acta

to afford

Chem.

Stand.,

1.2 mg of 1. -

837

(1983)

653.