Altamisin, a new sesquiterpene lactone from ambrosia cumanensis H.B.K.

TetrahedronLettersNo. 17, pp 1513 - 1514,

ALTAMISIN, FROM

1978.

Bert;=mon Press. Printedin Great Britain.

A NEW SESQUITERPENE AMBROSIA

CUMANENSIS

LACTONE H,B,K,

J. Barges*, M.T. Manresa, J.L. MartZin, C. Pascual y P. Vdzquez Departamento de QuPmica Orgdnica. Universidad Aut6noma de Madrid. Canto Blanco. Madrid-34. Spain. (Receivedin UK 22 February1978;

acceptedfor publication9 March 1978)

In this communication we report the isolation and structure determination of altamisin (I), a new sesquiterpene lactone whose structure 1 is related to that of the psilostachyins . Chloroform extraction of the aerial part of Ambrosia cumanensis H.B.K. 2 , collected from the outskirts of San Salvador (Central America) and known locally as Altamisa, after chromatography on Kieselgel 60, four crystalline products.

gave, The

first, C17H2405, m.p. 101-102° (n-hexane), CalD +34.90, was a new sesquiterpene lactone which we propose to name altamisin. The other three products were identified as psilostachyin , psilostachyin B and psilosta1 chyin C .

Altamisin contained one a,8 '-unsaturated y-lactone (Xmax 212 nm, -1 E 12,700); IR band at 1768 cm (Nujol). A second IR carbonyl absorption at 1725 cm -1 corresponded to the absorption expected for either a 6-lactone or an ester function. The presence of one tertiary hydroxyl group was indicated by an IR signal at 3530 cm -1 and a sharp singlet integrating for one proton at 64.88 in the NMR spectrum in deuterated dimethylsulfoxide. As expected, the signal disappeared on the addition to the NMR sample.

1513

of D20

1514

No. 17

The NMR for an

spectrum

of altamisin

a,f?'-unsaturated

psilostachyins';

a doublet

the C-6 lactonic

proton.

Hz) were

typical

spectrum

also

group ched

trum

spectrum

and a fragmentation

cleavage

of the C2-C3

The evidence ture

blished,

group,

biogenetic

configuration

stereochemistry

to

(J = 3.5

to a methyl

3 H, 61.72).

NMR methyl

group

atta-

methyl

group

The NMR spec-

ester:

a quartet

61.24, J = 7 Hz).

showed

a molecular

with

ion at m/e

the presence

(e.g., m/e

308

of the

Although

is fully

considerations

isolated

in accordance

the configuration suggest

that

since

from the genus

with

struc-

at C-5 was not estaaltamisin

has

the same

all pseudoguaianolides

Ambrosia

possess

the same

at this centre.

REFERENCES

1.

T.J. Mabry, 22,

1139

H.E. Miller,

X,

1629

hedron ~ 2.

P.C.

L.R. Tether,

Standley

and W. Renold,

H.E. Miller,

H.B.

W. Renold,

and T.J. Mabry, Kagan

Tetrahedron M.V.

Lak-

J. Org.

and H.E. Miller,

Chem.

Tetra-

(1966).

and S. Calderbn,

de El Salvador",

2nd Edition,

anemdfilos

San Salvador,

Kagan

W. Herz

(1966); T.J. Mabry,

22, 1943 cc

"Pblenes

H.B.

(1966); H.B. Kagan,

shimikantham,

e-

221, 59 %, allylic

bond).

at C-5 as psilostachyin,

and psilostachyins

the

The

group.

of an ethyl

(3 H,

to C-l

and 6.16

and of a second

singlet,

in accordance

so far described

I for altamisin.

evidence in

of one tertiary

assigned

characteristic

attached

at 65.46

methylene

was

of altamisin

pattern

side chain

found

characteristic

which

J = 7 Hz) and a triplet

The mass

further

(1 H, J = 9 Hz) was assigned

broadened

signals

provided

of the type

doublets

a hydroxyl

(slightly

also displayed

thyl ester

signals

bearing

bond

(2 H, 64.10,

64.70

at

Moreover,

3 H, 61.21),

to a carbon

on a double

system

of the C-11 exocyclic

exhibited

(singlet,

in CDC13

y-lactone

1975.

"Lista preliminar San Salvador,

de El Salvador",

de las plantas

1941;

Editorial

J.A.

Lagos,

Universitaria,