No. 7 2705

Chem. Pharm. Bull. 35( 7 )2705-2716(1987)

Acid-Induced Rearrangement of Triterpenoid Hydrocarbons

Belonging to the Hopane and Migrated Hopane Series

HIROYUKI AGETA,* KENJI SHIOJIMA and YOKO ARAI

Showa College of Pharmaceutical Sciences, 5-1-8 Tsurumaki,Setagaya-ku, Tokyo 154, Japan

(Received December 5, 1986)

The acid-catalyzed rearrangement of triterpenoid monoenes belonging to the hopane and

migrated hopane series with sulfuric acid and boron trifluoride etherate was investigated. By

selecting the reaction conditions, a variety of the monoenes of these series, including three new

compounds, 9ƒÀH-fern-7-ene (3c), 8ƒÀH-fern-9(11)-ene (4b), and adian-5(10)-ene (5b), were obtained.

For comparison, oleanenes and migrated oleanenes were also subjected to the same reaction.

Keywords•\acid-induced rearrangement; triterpenoid hydrocarbon; hopane, migrated

hopane; 9ƒÀ-fern-7-ene; 8ƒÀ-fern-9(11)-ene; adian-5(10)-ene; sulfuric acid; boron trifluoride

Introduction

The acid catalyzed rearrangement of triterpenoid monoenes is one of their most interesting features. Analyses of the reaction products have been used to establish the structures of the carbon skeletons of the so-called migrated triterpenoids, such as friedelin, 1)

glutinone (alnusenone),2) multiflorenol, 3) bauerenol,4) butyrospermol,5) and various kinds of triterpenoid hydrocarbons of the migrated hopane series.6,7) On the other hand, systematic investigations of the reaction products were also reported for friedel-3-ene with mineral8,9) and Lewis acid.10,11 ) In addition, experiments have been conducted on 3,4-epoxides of

friedelane,12) shionane,13) and D: A-friedolupane14) with boron trifluoride etherate. The

present paper deals with a mineral acid (H2SO4)- and a Lewis acid (BF3-etherate)-catalyzed rearrangement of triterpenoid monoenes having hopane and migrated hopane (neohopane, fernane, adianane and filicane) skeletons under various conditions (concentration of acid, temperature and reaction time). For comparison, some oleanenes and migrated oleanenes were also treated under similar conditions.

Results

Rearrangements of Hopenes with Sulfuric Acid

A similar reaction has been reported for zeorini 15) and hydroxyhopanone.16) The reaction

products of hop-22(29)-ene (1a)17,18) and hop-21-ene (1b)17) under various conditions are

shown in Table I. Treatment of la under mild conditions (1 N, 20 •Ž, 12 h) gave hop-17(21)-

ene (1c)17) in more than 90% yield with a small amount of neohop-13(18)-ene (2b).1.7) With 2 N

sulfuric acid, la afforded lc and 2b in various ratios according to the reaction temperature.

Interestingly, the temperature giving the highest yield of 2b was found to be 30 40 •Ž. With

4 N sulfuric acid at 20 •Ž for 96 h, la gave 2b in 95% yield.

The reaction products from lb were almost the same as those of la under similar

conditions. On the other hand, the reaction products mentioned above, lc or 2b, needed more

2706 Vol. 35 (1987)

drastic conditions as shown in Table I. In conclusion, the products formed from la, b, c and

2b were found to be mixtures of lc and 2b, and no other hydrocarbon was found. In addition ,

the fact that the ratios of reaction products lc and 2b formed from la or 2a with 2 N sulfuric

acid, were different, suggests that they were not simply an equilibrium mixture.

Rearrangements of Hopenes with BF3-Etherate

Next, la and lb were treated with boron trifluoriae-etherate in ether and in ether-acetic

acid (1 : 1). The reaction products under various conditions are summarized in Table II. In

ether solution, both la and lb gave lc as the sole product, and la was found to be more

reactive than lb. In ether-acetic acid solution, the formation of 2b was also observed. Thus,

boron trifluoride-etherate in ether was a very good reagent to produce lc from la or lb.

Rearrangement of Migrated Hopenes with Sulfuric Acid

Treatment of filic-3-ene (6)7) with sulfuric acid in acetic acid-benzene under very mild

conditions (1/4 N, 20 •Ž, 12 h) gave adian-5-ene (5a)7) and adian-5(10)-ene (5b)7 together with

unchanged starting material. Under more severe condition (1/2 N, 20 •Ž, 12 h) the products

were 5a, b and fern-8-ene (3b).6) Moreover, with 1 N sulfuric acid (20 •Ž, 12 h) 3b was formed

in a very pure state from 6, while with 2 N and 4N sulfuric acid at the same temperature, 6 gave

almost the same equilibrium mixture of 3b and a new compound, 8ƒÀH-fern-9(11)-ene (4b), in

the ratio of 2: 1. At a higher temperature (2 N, 40 •Ž, 12 h) 6 gave 4b, 3b, 2b and lc with

a second new compound, 9ƒÀH-fern-7-ene (3c). At 50 •Ž with 2 N sulfuric acid, 6 gave a mixture

of 4b, 3b, 2b and lc. Thus, treatment of a migrated hopene (6), yielded various kinds of

compounds, 5a, b, 4b, 3b, c, 2b and lc, according to the concentration of acid used and the

reaction temperatures.

TABLE I. Rearrangement Products from Hopenes

with H2 SO4

TABLE II. Rearrangement Products from Hopenes

with BF3-Etherate

No. 7 2707

Other natural compounds, adian-5-ene (5a),7 fern-9(11)-ene (4a),6) fern-7-ene (3a)7 and

neohop-12-ene (2a)19 were also subjected to rearrangement reactions. Compound 5a or 3a

gave the equilibrium mixture of 4b and 3b under the conditions used. Compound 4a furnished

3b under mild conditions (1 N, 20 •Ž, 12 h) and the mixture of 4b and 3b with stronger acid

(2 N, 20 or 30 •Ž, 12 h). However, at a higher temperature (2 N, 40 •Ž, 12 h), 4a gave 4b, 3b, c,

2b and lc as in the case of 6. At 50 •Ž with 2 N sulfuric acid, 4a gave a mixture of 2b and lc, as

in the case of la or lb (Table I). One of the reaction products (also found in some ferns), 3b,

seemed to be rather resistant to the acid, but at 2 N, 50 •Ž, or 4 N, 20 •Ž the products were very

similar to those formed from 6 under the same conditions. The other reaction product, 3c or

4b, yielded the mixture of 4b and 3b under the usual conditions.

Finally, 2a was found to be rather unstable to acid, giving 2b exclusively under mild

conditions. It was also found that 2a changes readily to 2b during chromatography on neutral

alumina.

Structures of New Reaction Products, 3c, 4b, and 5b

Compound 3c, mp 195-197 •Ž, was shown to have the molecular formula C3oHSO by

mass (MS) and elemental analysis. The MS fragments of 3c were similar to those of 3a, but

their relative intensities were remarkably different. The 1H-chemical shifts of eight methyls

and one olefinic proton of 3c were assigned, as shown in Table V, while those of three methyl

signals (C-25, C-26 and C-27) were found to. be different from those of the corresponding

TABLE III. Rearrangement Products from Migrated Hopenes with H2SO4

2708 Vol. 35 (1987)

TABLE IV. Physical Constants and Mass Fragments of the Compounds

No. 7 2709

signals of 3a. These observations suggested 3c to be 901-fern-7-ene, a 9H-isomer of 3a. To confirm the structure of 3c, 7-oxofern-8-ene (3d), prepared from 3b by CrO3 oxidation, was reduced by the Wolff-Kishner method, to give two isomeric hydrocarbons, one of which was

proved to be identical with 3a and the other with 3c [mp, relative retention time (RtR), and infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectra].

Compound 4b, mp 197-198 °C, was also indicated to have the molecular formula C30H5o by MS and elemental analysis. The fact that the fragmentation pattern of 4b (Table

IV) was indistinguishable from that of 4a, suggested that 4b is an isomer of 4a. The 1H-chemical shifts of four singlet methyl signals (C-23, C-24, C-27, and C-28) of 4b were very similar to those of 4a, while the other two (C-25 and C-26) were extraordinarily different. This observation was explained by considering the structures of 4a to be 8aH-fern-9(11)-ene (ring B boat), and 4b to be 801-fern-9(11)-ene (ring B chair), because the anisotropic effects of the 9(11)-double bond on the C-25 and C-26 methyls are different. Oxidation of 4b with 5e02

gave ferna-7,9(11)-diene (4c), which was identified by direct comparison with an authentic sample.6) Meanwhile, treatment of 4b with Cr03 afforded 8$H-fern-9(11)-en-l2-one (4e),

confirming the structure of 4b. The 1H-chemical shifts of methyl groups of 4e and its isomer

TABLE V. 11-1-Chemical Shifts (6) in CDC13 Solution (JEOL FX 100)

Assignments were confirmed by the CDC13--C6136 solvent shift method. All signals, unless otherwise stated, are singlets. Coupling constants are shown in parentheses.

2710 Vol. 35 (1987)

4d6) were assigned, as shown in Table V; one methyl signal (C-26) of 4e was observed 0.09 ppm

to lower fiels than that of 4d. Moreover, the olefinic proton signal of 4e was observed as a

singlet, while that of 4d was a doublet (J= 2.7 Hz). These observations clearly demonstrated

that 4e has the 8ƒÀH structure and 4d 8aH, because the bond angle of 801-11H had been

estimated as 50° and that of 8cxH-11H as 90°.20)

Finally, compound 5b, mp 208 209 °C, was also shown to have the molecular formula

C30HSO by high-resolution MS spectrum. The fragmentation pattern of 5b (Table IV)

indicated the compound to have a double bond in ring A or B. The 1H-N MR spectrum (Table

V) indicated the double bond to be tetrasubstituted and the chemical shifts of six singlet and

two doublet methyl signals were reasonably assigned when 5b was considered to be adian-

5(10)-ene2) This identification was confirmed by direct comparison (mp, RtR, and IR and 1H-

NMR spectra) with a sample derived from 5a via adian-1(10),5-diene (5c).71

Rearrangement of Migrated Hopenes with BF3-Etherate

The reactions of filic-3-ene (6)7) with boron trifluoride-etherate in ether solution were

much slower than those with sulfuric acid, and a considerable amount of the starting material

remained unreacted after 12 h, as shown in Table VI. Although the products were generally a

mixture of adian-5-ene (5a), adian-5(10)-ene (5b) and fern-7-ene (3a), the formation of 3a and

the absence of fern-8-ene (3b) were in contrast to the case with sulfuric acid. Treatment of 6 in

ether-acetic acid (1 : 1) with BF3-etherate (20%, 20 •Ž, 1 h) gave fern-9(11)-ene (4a) and fern-8-

ene (3b). In both benzene and chloroform solutions, the products from 6 were neohop-13(18)-

ene (2b) and hop-17(21)-ene (lc), together with a large amount of oily mixtures. Fern-9(11)-

ene (4a) was less reactive and no rearrangement had occurred under any of the conditions

TABLE VI. Rearrangement Products from Migrated Hopenes with BF3-Etherate

a) Oily by-products of lower molecular weight (GC-MS) were also formed.

No. 7 2711

mentioned above.

Rearrangements of Oleanenes and Migrated Oleanenes with Sulfuric Acid The reaction products formed from olean-18-ene (11), olean-12-ene (12a), friedel-3-ene

(16), multiflor-9(11)-ene (14a) and multiflor-7-ene (13a)21) with sulfuric acid under various conditions are summarized in Table VII. Compounds 11 and 12a gave mixtures of 12a, olean-13(18)-ene (12b), 18aH-olean-12-ene (12c) and 11. The formation of the former three was already known,22) but that of the last compound was found for the first time here. Compound 12a was found to be stable to acid, as compared with 2a. Compound 16 afforded glutin-5(10)- ene (15b) first under mild conditions, and the 12a in high yield. Compounds 14a and 13a also gave 12a as the main product. These observations indicate that the formation of 12a, b, c does

TABLE VII. Rearrangement Products from Oleanenes and Migrated

Oleanenes with H2SO4

TABLE VIII. Rearrangement Products from Friedelene with BF3-Etherate

a) Oily by-products of lower molecular weight (GC-MS) were also formed.

2712 Vol. 35 (1987)

not represent an equilibrium mixture as reported earlier.22)

Rearrangements of Friedel-3-ene (16) with BF3-Etherate The products formned from 16 with boron trifluoride-etherate under various conditions

are shown in Table VIII. In ether or acetic acid-ether solution, the reactions were rather slow, and the products were always 15a, b and 12a, together with the starting material. Thus, the formation of multiflorane derivative was not observed, in contrast to the case of the migrated

Chart 1

No. 7 2713

hopane (6). On the other hand, in benzene or chloroform solution, the reactions proceeded much more quickly and gave mixtures of four kinds of oleanane derivatives, 12a, b, c and 11. This situation was rather similar to the results with 16 in sulfuric acid, although the main

product was 12b with BF3 and 12a with acid.

Discussion

The acid-induced rearrangement of monoenes of the hopane and oleanane series with

sulfuric acid and boron trifluoride-etherate in ether are summarized in Charts 2 and 3. The

rearrangement of hopenes (la and lb) proceeds in a biogenetical direction (la•¨lb•¨lc•¨2b)

to give mixtures of lc and 2b, while that of the migrated hopenes (6, 5a, 4a, 3a and 2a)

proceeds in the opposite direction to biogenesis [2b(2a)•¨3a•¨3b•¨4a•¨5b(5a)•¨06] to afford

similar mixtures of lc and 2b. This situation is also similar in the oleanane series, but the final

products are 11 and 12a, b, c. The only exception was the formation of 13b from 12a (Table

VII).

The reaction products with sulfuric acid and with boron trifluoride-etherate are rather different. In the former case the products are generally the stable tetrasubstituted monoenes

(1c, 2b, 3b and 5b) except for 5a and the two new products (3c and 4b), and most of them do not occur naturally, while in the latter case some trisubstituted monoenes (3a, 4a and 5a) are formed and they are identical with natural products.

Chart 2. Direction of Rearrangement in the Hopane Series (•¨H2504,

－－→BF3)

a) Naturally occurring compounds.

Chart 3. Direction of Rearrangement in the Oleanane Series (•¨H2SO4,

－－BF3)

a) Naturally occurring compounds.

2714 Vol. 35 (1987)

When the reactions of the hopenes and the migrated hopenes are compared with those of the oleanenes and the migrated oleanenes, the latter compounds are much more reactive than the former. The reaction of the 3-ene (6) gave various kinds of fernene derivatives (3b, c and 4b with acid; 3a, b and 4a with BF3) and no neohop-12-ene (2a), while that of 16 gave olean-12-ene (12a) and no multiflorane derivatives with sulfuric acid as well as with BF3-etherate. It is noteworthy that, in the hopane series, fernene derivatives are widely distributed among fern

plants, while in the oleanane series, olean-12-ene derivatives are the most common natural products. The treatment of filic-3-ene (6) (or other migrated hopenes) with sulfuric acid and boron trifluoride-etherate can afford almost all kinds of known hopenes and migrated hopenes, such as 5a, b, 4a, b, 3a, b, c, 2b and lc, according to the conditions used. In many cases, the optimum conditions to produce a desired compound in high yield were found, as summarized in the Tables.

Experimental

Melting points were measured with a Yanagimoto microapparatus and are corrected. The [a]Ds were observed in

CHC13 solution (c = 0.3-0.6) at 22-24 C. 1H-NMR spectra were taken at 100 MHz by the FT method with

tetramethylsilane as an internal standard. MS spectra were recorded (direct inlet) at 70/eV and the relative intensities

of peaks are reported with reference to the most intense peak higher than m/z 100. Gas liquid chromatography (GLC)

was performed on a 1 m glass column containing Chromosorb G AW DMCS with 1.4% SE-30 at 260°C under N2.

Cholestane was used as an internal reference (its retention time was set at about 3.5 min), and the RtR values of

compounds are given (Table IV).

The starting materials were obtained as described below. Physical constants including MS fragments of the

starting materials and the reaction products are shown in Table IV, and 1H-NMR data in Table V.

Hop-22(29)-ene (la) and Hop-21-ene (lb) Hydroxyhopanone23) obtained from Dammar (Gum Copal C2)

was reduced by the Wolff-Kishner-Barton method to give hydroxyhopane, mp 256-258 •Ž, 1.0 g of which was

dehydrated by boiling with Ac20 (30 ml) and anhyd. K2CO3 (3.0 g) for 1 h. The products were separated into la

(0.63 g) and lb (0.27 g) by chromatography on 20% AgNO3-impregnated silica gel, and the pure products were

obtained after recrystallization from Me2CO.

Neohop-12-ene (2a), Fern-7-ene (3a), Fern-8-ene (3b), Adian-5-ene (5a), and Filic-3-ene (6) An n-hexane ex-

tract of the dried leaves (1.3 kg) of Adiantum monochlamys EATON (Pteridaceae),7,19) collected in August, was

chromatographed on silica gel and 20% AgNO3-silica gel. The corresponding fractions were recrystallized from

Me2CO. 2a 90 mg, 3a 450 mg, 3b 470 mg, 5a 470 mg, 6 310 mg.

Fern-9(11)-ene (4a) The dried leaflets (1.2 kg) of Dryopteris crassirhizoma NAKAI (Aspidiaceae),6) collected in

August, were treated as described above. 4a 410 mg.

Olean-l8-ene (11), Olean-12-ene (12a), Multiflor-7-ene (13a), Multiflor-9(11)-ene (14a), and Friedel-3-ene (16)

Specimens obtained from the rhizomes of Polypodium niponicum METT.21) were used.

General Procedure of Reaction with Sulfuric Acid The starting material was dissolved in C6H6 and added to

H2SO4 in AcOH at below the reaction temperature. The amount of the materials used was 1-4 mmol.

The solution was allowed to react in a isothermal apparatus (NKS LP-45-2, •} 0.5 •Ž) (10-50 •Ž) or in a

Coolnics Mixer (0 •Ž) under a nitrogen atmosphere, then added to ice-water, and extracted with n-C6H14. The extract

was washed with aqueous Na2CO3 and water, dried and evaporated to dryness. The residue was checked by GLC, gas

chromatography-mass spectrometry (GC-MS) and 1H-NMR spectroscopy to analyze the components qualitatively

and quantitatively. In many cases, the residue was chromatographed on neutral alumina and on 20% AgNO3-silica

No. 7 2715

gel to separate individual components. The products were recrystallized from Me2CO and identified by comparison

of melting points, RtR, and IR and 1H-NMR spectra with those of authentic samples.

General Procedure of Reaction with BF3-Etherate The starting material (1-4 mmol) was dissolved in fresh

BF3-etherate solution (v/v%) and treated in the same way as above.

9ƒÀH-Fern-7-ene (3c)•\Fern-9(11)-ene (4a) (120 mg) was treated with 2N H2SO4 solution (20 ml) at 40 •Ž for

12 h. The oily products were separated by repeated chromatographies on alumina (1 kg) followed by 20% AgNO3-

silica gel (40 g), with n-C6F114 eluent, to give 3b 44 mg, 2b 40 mg, 4b 8 mg, 3c 12 mg, and lc 4 mg in order of elution. 3c,

plates, mp 195-197 •Ž, was obtained by recrystallization from Me2CO. IR v KBr max cm-1: 820 (CH =C). Anal. Calcd for

C30H50: C, 87.73; H, 12.27. Found: C, 87.60; H, 12.42.

7-Oxofern-8-ene (3d) A solution of 1 g of fern-8-ene (3b) (1 g) in AcOH (80 ml), C6H6 (60 ml), and CHC13

(15 ml) was treated with Cr03 (0.4 g) in AcOH (50 ml) at room temperature overnight. The oily products were

extracted with Et20 and chromatographed on silica gel (100 g). The amount of the starting material recovered was

400 mg, and the fraction eluted with n-C6H14-C6H6 was purified by preparative thin layer chromatography [silica gel,

n-C61-114-Et0Ac (9 : 1)] followed by recrystallization from Me0H to give 3d, mp 185-186 •Ž. IR vKBr max cm-1: 1645.

UV ƒÉEtOH max nm (ƒÃ): 257 (10700). MS m/z. Calcd for C30H48O: 424.3704 (M+). Found: 424.3687.

Wolff-Kishner Reduction of 3d A solution of 10 mg of 3d in diethylene glycol was treated with Na (50 mg)

and anhydrous hydrazine (2.5 ml) at 210 •Ž for 15 h. The oily hydrocarbons (7 mg) obtained by Florisil chromatog-

raphy were found to be a mixture of 3a and 3c (1 : 4) by GLC and IR and 1H-NMR spectral examination.

8ƒÀH-Fern-9(11)-ene (4b) Fern-9(11)-ene (4a) (500 mg) was treated with 1 N H2SO4 solution (200 ml) at 20 •Ž

for 12 h in a nitrogen atmosphere. The oily products were separated by chromatography on alumina (Woelm grade I,

800 g, n-C6H14) to give 3b (320 mg), and 4b (130 mg), the latter of which was recrystallized from Me2CO to give plates,

mp 197-198 •Ž. IR vKBr max cm-1: 815 (CH =C). Anal. Calcd for C30H50: C, 87.73; H, 12.27. Found C, 87.79; H, 12.27.

Ferna-7,9(11)-diene (4c)•\A solution of 10 mg of 801-fern-9(11)-ene (4b) in AcOH (10 ml) was treated with

Se02 at 95 •Ž for 1.5 h. An n-C6H14 solution of the product was passed through a silica gel (5 g) column followed by

recrystallization from Me2CO to give 4c, plates, mp 201-202 •Ž. IR vKBr max cm -1: 3030, 1633, 1614, 822, 817, 795

(CH =C-C =CH). UV ƒÉEtOH max (ƒÃ): 232 (12900), 239 (14900), 248 (9800).

12-0xo-8fill-fern-9(11)-ene (4e) Compound 4b (50 mg) was oxidized with Cr03 (30 mg) in a AcOH (20 ml)

solution under reflux for 1 h. The product was chromatographed on a silica gel (5 g) column with n-C6H14-C6H6 to

give 32 mg of 4e, which was recrystallized from Me2CO to give plates, mp 188-190 •Ž. IR KBr max cm-1 : 1670 (CO),

1620, 860 (CH =C). UV ƒÉEtOH max nm (ƒÃ): 241 (10600). MS m/z. Calcd for C30H480: 424.3704 (M+). Found: 424.3708.

Adian-5(10)-ene (5b) Filic-3-ene (6) (60 mg) was treated with BF3-etherate (4 ml), Et20 (18 ml), and AcOH

(18 ml) at 20 •Ž for 12 h. The oily products were separated by repeated chromatography on 20% AgNO3-silica gel to

give the following fractions, in order of elution (n-C6H14): 3b 10 mg, 5b 10 mg, 4a 14 mg, 3a trace, 5a 8 mg, 6 12 mg.

Pure 5b, mp 208-209 •Ž, needles, was obtained by recrystallization from Me2CO. MS m/z. Calcd for C301150.

410.3912. Found: 410.3901.

Adiana-1(10),5-diene (Sc) A solution of 250 mg of adian-5-ene (5a) in C6H6 (10 ml) and AcOH (40 ml) was

heated with Se02 (270 mg) in a water bath for 1 h. The product was extracted with ether and passed through a silica

gel (20 g, contained a small amount of Ag powder) column in n-C6H14 to give 220 mg of 5c, which was recrystallized

from Me2CO, mp 209-210 •Ž. IR vKBr max cm1 : 821, 815. UV ƒÉEtOH max nm (ƒÃ): 232 (14800), 240 (16000), 248. (11000).

Catalytic Hydrogenation of 5c •\ A solution of 100 mg of Sc in EtOAc (8 ml) and AcOH (2 ml) was

hydrogenated with Pt02 for 4 h. The crystalline products were separated by chromatography on 20% AgNO3-silica

gel (10 g) to give 5 mg of 5b and 75 mg of 5a.

References and Notes

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2) J. M. Beaton, F. S. Spring, R. Stevenson and J. L. Stewart, Tetrahedron, 2, 246 (1958).

3) P. Sengupta and H. N. Khastgir, Tetrahedron, 19, 123 (1963).

4) F. N. Lahey and M. V. Leeding, Proc. Chem. Soc., London, 1958, 342.

5) W. Lawrie, W. Hamilton, F. S. Spring and H. S. Watson, J. Chem. Soc., 1956, 3272.

6) H. Ageta, K. Iwata and S. Natori, Tetrahedron Lett., 1963, 1447.

7) H. Ageta, K. Iwata and S. Natori, Tetrahedron Lett., 1964, 3413. The compound named isoadianene, mp

193.5-195 •Ž, [cdp - 108°, which was reported in this paper as adian-5(10)-ene, was found to be somewhat

impure 8fili-fern-9(11)ene by GLC and 'H-NMR spectral analysis. We would like to correct the description and

to discard the name isoadianene.

8) J. L. Courtney, R. M. Gascoigne and A. Z. Szumer, Chem. Ind. (London), 1956, 1479.

9) J. L. Courtney, R. M. Gascoigne and A. Z. Szumer, J. Chem. Soc., 1958, 881.

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12) M. TOri, T. Tsuyuki and T. Takahashi, Bull. Chem. Soc. Jpn., 50, 3381 (1977).

2716 Vol. 35 (1987)

13) K. Tachibana, M. Tori, Y. Moriyama, T. Tsuyuki and T. Takahashi, Bull. Chem. Soc. Jpn., 50, 1552 (1977). 14) Y. Yokoyama, Y. Moriyama, T. Tsuyuki and T. Takahashi, Bull. Chem. Soc. Jpn., 54, 234 (1981). 15) D. H. R. Barton, P. de Mayo and J. C. Orr., J. Chem. Soc., 1958, 2239. 16) H. Fazakerley, T. G. Halsall and E. R. H. Jones, J. Chem. Soc., 1959, 1877. 17) G. V. Baddeley, T. G. Halsall and E. R. H. Jones, J. Chem. Soc., 1960, 1715. 18) H. Ageta, K. Iwata and K. Yonezawa, Chem. Pharm. Bull., 11, 408 (1963). 19) H. Ageta, K. Shiojima and Y. Arai, Chem. Commun., 1968, 1105. 20) E. W. Garbisch, Jr., J. Am. Chem. Soc., 86, 5561 (1964). 21) H. Ageta and Y. Arai, Phytochemistry, 22, 1801 (1983). 22) G. Brownlie, M. B. F. Fayez, F. S. Spring, R. Stevenson and W. S. Strachan, J. Chem. Soc., 1956, 1377. 23) W. J. Dunstan, H. Fazakerley, T. G. Halsall and E. R. H. Jones, Croat. Chim. Acta, 29, 173 (1957).