A new sesquiterpene hydrocarbon from laurencia glandulifera

Tetrahedron LettersNo.40,pp, 3619-3624,1965, PergamenPressLtd. Printedin GreatBritain.

A NEW SESQUITERPENEHYDROCARBORFROM LAURBFICIA GLAIVDULIFSRA1

Toehi Irie, Yumiko Yasunari,Teruaki Suzuki, Borio Imai, gtauro Kurosawa,and Tadashi kfaaaamune D8partmentof Chemistry,Faoulty of Science,HokkaldoUniversity, Sapporo,Japan {Received21 &aguet1965) In the preoedingpaper* we reportedon the 8truOtur8of laurenoin, a oompoundoontainingbromtne obtainedfrom LaurenoiaKIandulifera Ktftzing.W&i18 Obata and Fukush13pointed out the presenceof a sesqulterpenehydrooarbonin the

same

algae, a new hydrocarbon,C15H20, was

isolatedon our further examinationand designatedlaurena. In this paper, the hydrocarbonwill be shown to have structureI on the basis of argumentsmentionedin the following. Laurene (I) was obtainedin ca. 0.11% yield by ohromatographyof a neutral fractionobtainedby steam distillationof methanol extraotsof the e8an88d.4 The hydrocarbon,b.p. 131-133°/21 mm, (EtOH),hz

[m]i3+48.7'

253 (2SOf, 259 (280). 265 (280) and 274 mp (& 240),3=

1653, 1512, 1017, 875, 812 and 725 cm-1, was analyzedfor C15A20.5 The n.m.r. speotrum (60 ?&cIc., in CC14) shored peaks at 3.01 (4H, s),6 5.19 (2H, q, Y = 1 c.p.s.1, 7.69 (3H, 8). 8.71 (3H, 8) and 9.322(3H, d, J = 7 c.p.8.). All

these

spectraldata indicatedthe presenceof a

tolyl (pyobablyp-substituted), a terminalmethylene,a secondarymethyl and a tertiarymethyl group. In view Of the number Of 8it8S Of unSatwation of laurene,another carbon ring must be present in the molecule.

3619

3620

3

No.40

4

5

6

7

8

9

kw

3

4

5

6

-I

8

9

10T ,

Fig. 1. n.m.r. Spectra of laureneand isolaurene(60 MC., in 0X4) Oxidationof I with oemiwn tetroxidein ether-pyridine affordeda &lYCOl (II), C15h220*, [a]i3+40°, $ z3 and

3520, 3380, 1508, 1012, 975

812 cm-l, n.m.r. 3.05 (4H, I). 5.95 (2H, n), 7.73 (3H, 81, 8.54 (3H,

II)and 9.382(38, d, J - 7 a.p.8.). When treatedwith periodicacid, II wan convertedto a ketone (III),C14H180, [a)E3+70°, which was found to have a fire-memberedring carbonylgroup ($_

1737 om-1) and probably

a methylenegroup adjacentto the carbonglgroup ($_

1410 cm-').

The n.m.r. spectrumof III showed peaks at 2.70-2.99 (4li,m; aromatic protons),7.66 (3H, s; aromatiomethyl), 8.64 (3H, s; tertiarymethyl) and 9.042 (3H, d; eeaondarymethyl). This ketone showed a positive Cotton effect and gave a crystallinesemicarbazone, m.p. 227-229'. Treatmentof I with silicicacid In petroleumether yielded an isomerichydrocarbon,iaolaurena(IV), C15H20, b-p. 140-142'/21 mm, -1 gfilm max 1510, 1015, 819 and 720 cm . While the n.m.r. @I;" +1013,7O, spectrumof IV exhibitedabsorptioneat 3.04 (4H, s), 7.76 (3H, 8) and 8.67'2(3H, 8) which were comparableto those due to aromaticprotons (3.01x 1. an aromaticmethyl group (7.69-t)and a tertiarymethyl group (8.712) IofI respectively,the signals due to the methylene (5.197)

3611

No.40

C7H7-h

c7H7 \ 0

-R

III

I

\

CH

IV

CH VI

V

and the secondary methyl groups (9.327)

of I were replaced by those at

s)-', which were attributable to methyl groups

8.30 (3H, 8) and 8.63T(3H, attached to olefinic carbon.

Hence, the isomerizatlon Involves migration

of the exo-cyclic double bond to an endo-cyolic one to zhloh two methyl groups are attached and, therefore, the terminal methylens and the secondary methyl groups must be located on vicinal carbons In I, as far as no skeletal change occurs during the isomerization.

This was sup-

ported by the formation of a ditertlary glyool (V), m.p. 114-116', ,)CHCl _ 3 3320, 1512, 1069, 1017 and 810 cm-', on treatment of IV with osmium tetroxlde; that is, the n.m.r. spectrum of V exhibited two sharp signals at 8.82 and 8.902

due to the methyl groups on vlcinal carbons

bearing hydroxyl group instead of those at 8.30 and 8.63P

in IV.

All these results indicate that I Is the most preferable structure for laurene,

8

since the possibility of formula VI is ruled out by the

presence of optical activity In isolaurene.

It is evident on the basis

of the high 'L-value of the secondary methyl signal in the n.m.r. spectrum of laurene or the glycol II that the secondary methyl group Is cis oriented to the tolyl group. 9 -

No.40

The

structure

X for laureoe has now been oonfirmedby the synthesis

(VII) was methylated of the ketone III. 2-(p-Tclyl)-oyclcpentanone10 rith methyl iod2de and sodium amide to yield 2-methyl-2-(p-tolyl)-cyclopentanons.(VIfI),b.p. 124-126'/5.5 mm, 4:

1737, 1408 and 810 cm-',

n.m.r. 2.90 (48, a), 7.72 (3B, 8) and 8.72% (3R, 8). The treatmentof VIII with methyl lithium in ether affordedatereoisomereof 1,2-dimethyl2-(~-tolyl)-cyclopentanol (IX). On acid dehydration,both the cis- and the ax-isomer (X), $ E3

I1 gave the same 2,3-dimethyl-3-(g-tolyl)-oyclopentene

1505, 1072, 1020 and 820 cm", n.m.r. 2.93 (4R, a), 4.57

(Ui, m), 7.70 (3H, a), 8.55 (38, d, J I 2 a.p.8.) and 8.582 (3R, 8). On hydroborattcn,the oyolopenteneX gave mainly m-2,3-dimethyl-3-(p3630, 3460 and 1042 cm-l, n.m.r.

tolyl)-cyalopentanol (X),12 $=3

3.00 (4R, e), 7.72 (3H, 8). 8.60 (3H. 8) and 9.387 (3H, d, J = 7 c.P.s.).

1

D

C7H7

C7H7 @

6H

VII R=H VIII R - CH

3

IX

X C7H1--_ H XI

ij

NO.40

3623

This alcohol was oxidised with chromic oxide-pyrldlne to yield m-2,3dimethyl-3-(p-tolyl)-cyclopentenone

(XII), ?z13

1737, 1515 end 1410 cm-l,

n.m.r. 2.70--2.99 (4H, m), 7.66 (3H, 8). 8.84 (3H, 8) and 9.047 J = 7 c.P.s.), the semicarbasone, m.p. 214-215'.

(3H, d,

The-infrared and n.m.r.

spectra and Rf-values on the thin layer ohromatograms of the s-ketone

XII

and its semicarbasone thus obtained were completely identical with these of the ketone III and its semicarbazone obtained from laurene.

Acknowledgments

-

The authors wish to thank to Dr. Iemasa Yamads

of Department of Botany, this Faculty, for collection of the seaweed and to Mr. Shigeso Shimokawa for measurments of the n.m.r. spectra.

REFERENCES

(1)

Part III of "Constituents from Marine Plants"; Part II, reference 2.

(2)

T. Irie, 1. Suzuki and T. Masamune, Tetrahedron Letters, 1091 (1965).

(3)

Y. Obata and S. Fukushi, J. Aaricult. Chem. Sot. Japan, 27, 331 = (1953).

(4)

The seaweed was collected in August at Oshoro Bay, Hokkaido.

(5)

Satisfactory analyses were obtained for the new compounds ilsted in this report.

(6)

8: singlet, d: doublet, q: quartet, and m: multiple&.

(7)

The absorption at 8.632

appears in the extraordinarily high field

as that due to methyl group attached to olefinic carbon, and this abnormality would be caused by magnetic anisotropy of benzene ring, cf. reference 9.

(8)

Laurene might be probably a precursor of aplysin, a sesquiterpene containing bromine isolated from Sea rat (Aplysla kurodai Raba) by S. Yamamura and Y. Hirata (Tetrahedron, I.'& 1485 (1963)). since Sea rat feeds on Laurencia. (Professor Jun Tokida, the Faculty of Fisheries, this University, private communication).

No.40

3621

(9)

C'f. 0. L. Chetty and S. Dev, Tetrahedron Letters, 73 (1964) and J. A. Steele, L.

A.

Cohen and E. losettig, J. Amer. Chem. Sec.. 2,

1134 (1963). (10) X. Pislor and C. B. Hammermesh, u.,

2.

1590 (1955).

(11) The terms "cis" and "trans" refer to the relative configuration of methyl groups in vioinal carbons Cl and C2. One isomer in the spectrum of which a peak due to the methyl group on Cl appeared at was assigned -tie-compound, and another which showed the corresponding peak at 9.132 was assigned 8.857

(12) Rydroboration involves cis addition from the less hindered side of the double bond, H. C. Brown and G. Zweifel. u., El, 247 (1959); $2, 2544 (1961); g,

393 (1964).