Erymelanthine, a new type of erythrina alkaloid containing a 16-azaerythrinane skeleton

Tetrahedron Letters,Vol.24,No.46,pp Printed in Great Britain

5@67-5070,1983

A NEW TYPE OF ERYTHRINA

ERYMELANTHINE,

16-AZAERYTHRINANE

Ermias Institut

Dagne

fiir Organische

Gerhard-Domagk-Stral3e

Summary: represents

the first member

a 16-azaerythrinane

As part we have

isolated

279

Kenya

1380, nm

1340,

dd, J=12+5 3.55

Hz, H-4

Hz, H-14),

1 differs

3.75

ever,

occurs

two singlets

312

(12); IR

(m, H-10

species with

to occur

from EthiopiaA

erysovine

in southern

properties:

!M+, C,8H20N203,

CDC13):

(CHC13): UV

6 1.91

eq

(m, H-IO,,),

3.96

(2) Ethiopia,

2950,

1720,

(361, 281

(EtOH) Amax(

(dd, J=10+2

1590,

270

4.00

3.31

1430,

2.51

(br.

(s, 0CH3),

(m, H-31,

Hz, H-21,

(loo),

(3000), 230

Hz, H-4,,),

(m, 2H, H-11),

[ali

160-161°C;

297

(s, C02CH3),

6.61

mp

79%),

(dd, J=l2+10

1, 3.10

alkaloids

of a second

attached

in the spectrum

atom.

4

5.76

8.00

(d, J=l

so far from Erythrina Its MS exhibits

of the 1,6-diene

series5,

to rings A, B and C correspond

of erysovine

in the aromatic

region.

having

shifts

chemical

isolated

nitrogen

for an alkaloid

for the protons

observed

containing

(br. d, J=l Hz, H-17).

pattern

those

melanacantha,

alkaloid

(l) along

and spectral

930, 820/cm;

from all the other

fragmentation

1, FRG

3

(d, J=lO Hz, H-l),

ties by the presence

signals

1100,

2.77

eg)'

6.10

8.50

Bonn

a tree known

193

49),

(400 MHz,

(m, 2H, H-8),

(br. s, H-7),

der Universitat

of Erythrina

erymelanthine

MS: m/z

1230,

'H NMR

(8000);

1, D-5300

and Tanzania.

(C15H13N2,

1290,

und Biochemie

on the alkaloids

physical

(c = 0.11, MeOH); (28), 221

Steglich*

of a new type of erythrina

of E. melanacantha,

1 has the following +87O

A

SKELETON'

from the seeds of Erythrina

a new alkaloid

northern

CONTAINING

skeleton.

of our studies

from the seeds Somalia,

isolated

Erymelanthine,

ALKALOID

and Wolfgang Chemie

OO40-4039/83 $3.00 + .OO 01983 Pergamon Press Ltd.

Whereas between

5067

(2). A dramatic in 2 and other

spe-

the normal and the 'H NMR closely

difference, erythrina

to how-

alkaloids

6.5 and 7.0 ppm may be observed

506 8

for H-14

and H-17,

(6 8.00 and 8.50, pyridine

unit

positions.

the corresponding respectively).

signals

This may be explained

in ring D, substituted

From

the coupling

by a carbomethoxy

constant

ring.

at 6 8.50 is broadened

by benzylic

be shown

experiments.

as could

thrinane

derivative

occupy

by decoupling

and is in full accord

at unusually

group

the aromatic

coupling This

of a

at one of the a-

a- and B'-positions

with

low field

by the presence

Hz between

that

atC(11)

protons

of J=l

can be concluded The signal

these

of 1 appear

signals

it

of the pyridine with

the protons

excludes

a 15-ery-

a 16-azaerythrinane

structure

B

for erymelanthine.

.

1

Structure melanthine

2 is further

with

C(1)

to C(11)

both

alkaloids.

Table

Carbon 1

2 3 4 5 6 7 8 10 11

2

those

supported

recently

by comparison

published

in rings A, B and C exhibit The chemical

1. I3 C NMR data

shifts

of the

nearly

identical

6

124.9

131.7 75.4 40.4 66.5 145.7 123.4 56.1 42.3 21.3

d d d t s

in the pyridine

shifts

for for

ring of 1

(2) in CDCl3

1 =

c

J=l56 Hz 154 137 126 -

: t t t

a) Sharp singlet in H-coupled d) Qa, 3JcH= 4.5 Hz.

chemical

(1) and erysovine

1 =

No.

NMR data of ery-

for erysovine 6 (table 1). Signals

of the carbons

of erymelanthine

"C

163 134 132 125

1%mm

125.6 132.0 75.9 41.4 66.8 142.4 122.4 56.8 44.0 24.2

spsctrum-I

12 13 14 15 17 CO,CH, CO,CH, OCH,

134.0 140.4 122.1 149.6 150.4 165.9 52.8 56.5

s

-

:a

158 171 141 135

itI s

b) Dt, 3JCH= 3 Hz; c) d,

3

125.2 131.5 111.0 145.6 112.5 55.7

JCH= 11 Hz;

5069

are in close 6 149.6 and ring occur split

agreement

150.4, which as a singlet

into triplets

further

support

by

C NMR

Jj

I

spectrum

4ax

12 Hz) for these

region

adds

vage

1

coupling

gives

respectively, with

to two signals

support

biosynthetic between

to this

C(16)

1 must

and C(17)

of E. melanacantha

erythrina diol

have

alkaloids

proposed

melanthine

seems

The possibility

to advocate that

ammonia

10

work-up

with

acantha

by a procedure

2 with lends

two pathwpys

a is an artefact was excluded

at 1720/cm. J3

constants

I

4es

(5 and

stereochemistry.

in the 220-260

involve

nm

extradiol

by formation

ammonia.

clea-

of the pyridine

The co-occurrence

of

to this hypothesis.

for the conversion which

cleavage.

involve The

of aromatic either

isolation

intraof ery-

pathway. formed

by isolating

ammonia

may

support

[C(16)-C(17)]

the latter

omitting

165.9 in the

assignment.

followed

into a- and B-erythroidines,

[C-(15)-C(16)I or extradiol

lends

at C(15).

of an IR band

the same

at

further

This

at 6 52.8 and

possess

to erymelanthine

l and 2 in the seeds

9

group

from the coupling

stereochemical

of the intermediate

et al.

being

at C(11).

of i and 2 particularly

route

The signals

a Since 1 and 2 show the same values

ring by condensation

Barton

the protons

7

of the pyridine

the latter

for the presence

constants,

of the CD spectra

systems.

of the carbomethoxy

rise

spectrum.

coupling

of erysovine

of similar

at C-3 may be deduced

H NMR

further

A plausible

and doublet, 3JCH

data

to the a- and a '-positions

and is responsible

in the

The similarity

correspond

group

The stereochemistry and

literature

for the positioning

The carbomethoxy 13

with

during

from

intermediate

1 from the seeds the extraction.

2 during of E. -- melan-

5070

Acknowledgment: Alexander

von Humboldt-Stiftung.

availablethrough

References

a grant

The Bruker

from the Deutsche

to Professor

E. Dagne

acknowledges

a fellowship

from the

WM 400 NMR spectrometer

was made

Forschungsgemeinschaft.

and Notes

1) Dedicated 2)

E. D. gratefully

Sir Derek

and W. Steglich,

Barton

on the occasion

Phytochemistry,

of his

65

th

birthday.

in press.

3) The seeds

of -* E melanacantha were collected in April 1982 in south Ethiopia from trees growing in the province of Borana, 58 km west of Negelle town at

an altitude Tadesse

of 980 m above

of the Biology

description

of this plant

E. Milne-Redhead Crown

Agents,

4) Recently atom

sea level.

Department,

an erythrina

folius:

M. Juichi, (1981).

555

5) R.B. Boar 6) A.S.

alkaloid,

R.M.

(Eds.), Flora --

erythramide,

group

Y. Fujitani,

and D.A. Widdowson,

Chawla,

was

identified

University. Polhill

by Ato Mesfin

For a botanical and B. Verdcourt

of Tropical

in

East Africa, -____

1971, p. 552.

in form of a carboxamino

16,

Ababa

see: J.B. Gillet,

and R.M. Polhill

London

The plant

Addis

T. Shingu

J. Chem. - --

S. Chunchatprasert

possessing

has been

an extra

B, 1970,

Jackson,

nitrogen

from Cocculus

and H. Furukawa,

Sot.

and A.H.

isolated

lauri-

Heterocycles,

1591.

Org. s.

Reson.

11,

39

(1983). 7) E. Breitmaier

and G. Bauer,

13

C-NMR-Spektroskopie,

G. Thieme,

Stuttgart

1977,

p. 367. 8) S.F. Dyke and S.N. Quessy The Alkaloids, 9) D.H.R.

a, IO)

Vol.

Barton,

R.D. Bracho,

C.J.

Manske

and R.G.A.

Rodrigo

Fress,

New York

Potter

and D.A. Widdowson,

(Eds.),

1981, p. 11. J.C.S. ---

Perkin

2278.

Cf. the formation H.-G.

in R.H.F.

17, Academic

Floss,

(Received

of gentianine

U. Mothes

in Germany

from gentiopicroside

and A. Rettig,

1 September

1983)

2. Naturforsch.

or swertiamarine: 19 b, 1106 --

(1964).

I,