Total synthesis of (±)-cis-5-hydroxycalamenene

Article abstract of DOI:10.1080/00397910802026204

A total synthesis of (±)-cis-5-hydroxycalamenene 1 has been achieved from tetralone 5, which in turn was prepared from 5-methoxy-α-tetralone 3. Grignard reaction of compound 5 with isopropylmagnesium chloride, followed by dehydration and aromatization, provided the substituted naphthalene 7 whose conversion to (±)-cis-5-hydroxycalamenene 1 was accomplished by demethylation, formylation, and hydrogenation. Copyright Taylor & Francis Group, LLC.

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Total Synthesis of (±)- Cis -5-
Hydroxycalamenene
Po S. Poon Ng a & Ajoy K. Banerjee a
a Centro de Química, Instituto Venezolano de
Investigaciones Científicas (IVIC) , Caracas,
Venezuela
Published online: 18 Aug 2008.
To cite this article: Po S. Poon Ng & Ajoy K. Banerjee (2008) Total Synthesis of (±)-
Cis -5-Hydroxycalamenene, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 38:13, 2261-2268, DOI:
10.1080/00397910802026204
To link to this article: http://dx.doi.org/10.1080/00397910802026204
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Synthetic Communications1, 38: 2261–2268, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802026204
Total Synthesis of ( )-Cis-5-Hydroxycalamenene
Po S. Poon Ng and Ajoy K. Banerjee
´
Centro de Quımica, Instituto Venezolano de Investigaciones
´
Cientıficas (IVIC), Caracas, Venezuela
Abstract: A total synthesis of (ꢀ)-cis-5-hydroxycalamenene 1 has been achieved
from tetralone 5, which in turn was prepared from 5-methoxy-a-tetralone 3.
Grignard reaction of compound 5 with isopropylmagnesium chloride, followed
by dehydration and aromatization, provided the substituted naphthalene 7 whose
conversion to (ꢀ)-cis-5-hydroxycalamenene 1 was accomplished by demethyla-
tion, formylation, and hydrogenation.
Keywords: (ꢀ)-cis-5-hydroxycalamenene; Grignard reaction; 5-methoxy-a-
tetralone; Terpene
INTRODUCTION
(ꢀ)-Cis-5-hydroxycalamenene 1 is a phenolic sesquiterpene, isolated[1,2]
from the essential oil of European liverwort Bazzonia tricrenta and trilo-
bata, for which the cis-structure was assigned on the basis of compre-
1
hensive spectral studies. The H NMR spectrum of the trans isomer,
prepared by the acid-catalyzed cyclization[3] of the phenolic sesquiterpene
Xanthorrihal 2,[4] was distinctly different from that of natural product
5-hydroxycalamenene 1. Furthermore, the (ꢀ)-cis-5-hydroxycalamenene
1 has also been detected as a principal component in the essential oil
of Myrica rubra var. tree,[5] and the stereostructure of 1 was revised to
be (1R, 4R)-cis-5-hydroxycalamenene by X-ray crystallographic analysis
of its p-bromobenzoate derivative.[6]
Received in the USA January 17, 2008.
Address correspondence to Ajoy K. Banerjee, Centro de Quimica, IVIC,
Apartado 20632, Caracas 1020-A, Venezuela. E-mail: abanerje@ivic.ve,
ppoonng@ivic.ve
2261

2262
P. S. P. Ng and A. K. Banerjee
Recently, the antioxidant and antimicrobial activities[5,7] of the essen-
tial oils from leaves, bark, and root of Myrica rubra, which result from
the large content of 5-hydroxycalamenene, have been reported. In
Scheme 1. (i) CH3MgBr, (CH3CH2)2O; (ii) HCl 6 N; (iii) H2, Pd=C 5%; (iv)
NaClO2, t-BuOOH, CH3CN, H2O; (v) i-PrMgCl, THF; (vi) HCl 6 N; DDQ,
CH2Cl2; (viii) HBr 48%, CH3COOH; (ix) (CH2O)n, MgCl2, (CH3CH2)3N,
THF; (x) H2, Pd=C 10%, 500 psi.

Total Synthesis of ( )-Cis-5-Hydroxycalamenene
2263
addition, 5-hydroxycalamenene exhibit strong antifungal activity against
P. oryzae.[8]
Because of their notable biological activities, two groups have
attempted synthetic studies of the (ꢀ)-cis-5-hydroxycalamenene 1.
In 1982, Sangaiah and Rao[9] first reported the total synthesis of 5-
hydroxycalamenene in which the relative stereochemistry of the isopropyl
and methyl group remained unspecified. Tanaka and Adachi[10] reported
the synthesis of (ꢀ)-cis-5-hydroxycalamenene 1 and confirmed the
stereochemistry of the naturally occurring compound 1. The synthetic
routes of the published procedures are lengthy.
In a continuation of our earlier work[11] on terpene compounds, we
set out to develop a simple and concise route for the synthesis of (ꢀ)-
cis-5-hydroxycalamenene 1 (Scheme 1).
RESULTS AND DISCUSSIONS
Tetralene 4, prepared[11] from tetralone 3, was oxidizedwith sodium
chlorite and tert-butyl hydroperoxide[12] to obtain tetralone 5 in 60%.
This method afforded the most satisfactory result compared to the other
reagents such as CrO3-MeCOOH,[13] pyridinium chlorochromate,[14] and
pyridinium dichromate[15] because of the difficult workup of the envir-
onmentally hazardous chromium residues. Tetralone 5 was treated with
isopropyl magnesium chloride in tetrahydrofuran to obtain the
compound 6.
This supposedly straightforward transformation proved to be much
more complicated than we had anticipated. Considerable difficulty was
encountered in finding proper conditions to effect the 5!6 conversion.
The best result was obtained by treatment of tetralone 5 with isopropyl
magnesium chloride in tetrahydrofuran (3 equivalents). The difficulty
encountered in the Grignard reaction may be due to the 5-methoxy group
which hindered attack of the bulky Grignard reagent on the carbonyl
group to afford the alcohol in high yield. The resulting alcohol
was treated with hydrochloric acid (6 N) to afford product 6. Dehydro-
genation with 2,3-dichloro-5,6-dicyano benzoquinone (DDQ) gave the
compound 7, which on demethylation with hydrobromic acid and acetic
acid furnished the naphthalene 8. Its conversion into the aldehyde 9 in
80% yield was achieved by heating with paraformaldehyde, magnesium
chloride, and triethylamine.[16] To complete the synthesis of hydroxycala-
menene, all that was required the conversion of the formyl group to a
methyl and partial hydrogenation of the aromatic ring containing the
isopropyl group. These were effectively accomplished by carrying out
the catalytic hydrogenation of compound 9 with Pd=C (10%) under

2264
P. S. P. Ng and A. K. Banerjee
high pressure (500 psi) at room temperature. The resulting compound
was identified as (ꢀ)-cis-5-hydroxycalamenene 1, whose spectroscopic
1
properties (NMR H and 13C) were identical with those reported.[2,10]
CONCLUSIONS
In conclusion, an efficient synthesis of (ꢀ)-cis-hydroxycalamenene has
been developed from 5-methoxy-a-tetralone. The present method has
two merits compared with the published synthesis[9,10]: (a) our procedure
involves 10 steps, while the reported method requires 16 steps and (b)
the overall yield of our procedure is higher (8%) if compared with pub-
lished yield (5.5%). The present synthetic route proceeds via intermedi-
ates, which can be utilized for the synthesis of other representative
members of this group (calamenenes) of natural products.
EXPERIMENTAL
Unless otherwise stated, IR spectra were taken on Nicolet FT instrument.
1H NMR and 13C NMR spectra were recorded on Brucker AM 300-Hz
instrument in CDCl3 using tetramethylsilane (TMS) as internal standard.
Mass spectra were run on gas chromatograph Hewlett Packard 5890
Quadrupolar 5972 Series S. Column chromatography was performed
on silica gel (Merck grade 60, 70–230 mesh). All organic extracts were
washed with brine, dried (MgS04), and evaporated under reduced press-
ure. The spectral and analytical data of all new compounds have been
reported in the Experimental section. Microanalyses were carried out at
the Chemistry Department, IVIC, Caracas.
3,4-Dihydro-8-methoxy-4-methylnaphtha len-1(2H)-one 5
To
a stirred solution of compound 4 (0.10 g, 0.56 mmol) in
CH3CN=H2O (3:1, v=v) (8 ml), tert-butyl hydroperoxide (0.4 ml=2.8 mmol,
70% aqueous solution) and sodium chlorite (0.076 g, 0.67 mmol) were
added. The reaction mixture was heated at 50ꢁC for 12 h, then diluted
with sodium sulfite solution (10%), and extracted with dichloro-
methane. The organic extracts were washed with water and saturated
aqueous NaHCO3, dried, and chromatographed (hexane=ether 1:1) to
obtain the tetralone 5, a colorless liquid (0.063 g, 60%). nmax (KBr)
1676.08 cmꢂ1 (CO); m=z: 191 (Mþ þ 1), 190 (Mþ), 161 (Mþ-COH),
133 (Mþ-COH-C2H4); NMR 1H d: 1.32 (d, 3H, CH3, J ¼ 7.1 Hz),
1.8–1.9 (m, 1H), 2.1–2.2 (m, 1H), 2.6–2.7 (m, 2H), 3.0–3.1 (m, 1H),

Total Synthesis of ( )-Cis-5-Hydroxycalamenene
2265
3.86 (s, 3H, OCH3), 6.81 (d, 1H, J ¼ 8.4 Hz), 6.85 (dd, 1H, ArH,
J ¼ 7.8 Hz, J ¼ 8.0 Hz), 7.39 (dd, 1H, ArH, J ¼ 7.9 Hz, J ¼ 7.2 Hz)
ppm; NMR 13C d: 20.97, 29.56, 33.62, 37.45, 55.93, 109.88, 119.41,
121.58, 134.02, 151.59, 160.00, 197.64 ppm. Anal. calcd. for C12H14O2:
C, 75.76; H, 7.42. Found: C, 76.01; H, 7.56.
1,2-Dihydro-4-isopropyl-5-methoxy-1-methylnaphthalene 6
To the isopropylmagnesium chloride (2 M, 0.65 ml, 1.26 mmol) in dry
tetrhydrofuran (5 ml), tetralone 5 (0.16 g, 0.84 mmol) was added dropwise
and stirred over 48 h at room temperature. The reaction mixture was
poured into saturated aqueous ammonium chloride and extracted with
diethyl ether. To the resulting organic extract, hydrochloric acid (6 N,
8 ml) was added and stirred for 3 h at room temperature. The aqueous
phase was extracted with ether, and the combined extracts were dried
and concentrated. The residue on chromatographic purification (hexa-
ne=ether 9:1) yielded the olefin 6 as a light yellow liquid (0.11 g, 57%).
nmax (KBr) 1676.08 cmꢂ1 (CO); m=z: 216 (C15H20O, Mþ), 173 (Mþ
-C3H7), 158 (Mþ-C4H9); NMR 1H d: 1.05 (2d, 6H, -CH(CH3)2,
J ¼ 6.7 Hz), 1.16 (d, 3H, CH3, J ¼ 7.0 Hz), 1.9–2.0 (m, 1H), 2.2–2.3
(m, 1H), 2.70 (sept., 1H, -CH(CH3)2, J ¼ 6.8 Hz), 3.80 (s, 3H, OCH3),
5.85 (t, 1H, J ¼ 4.7 Hz), 6.72 (d, 1H, J ¼ 8.2 Hz), 6.82 (d, 1H,
J ¼ 7.5 Hz), 7.12 (t, 1H, ArH, J ¼ 7.9 Hz) ppm; NMR 13C d: 18.74,
22.40, 22.82, 29.88, 30.46, 33.65, 55.40, 110.07, 118.90, 120.54, 123.90,
127.21, 143.15, 145.32, 156.25 ppm. Anal. calcd. for C15H20O: C, 83.28;
H, 9.32. Found: C, 83.55; H, 9.48.
8-Isopropyl-5-methylnaphtalen-1-ol 8
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (0.30 g, 1.33 mmol) was
added to a solution of compound 6 (0.24 g, 1.11 mmol) in dichloro-
methane (6 ml) at 0–5ꢁC. The mixture was stirred at room temperature
for 1 h, concentrated, and chromatographed rapidly (hexane) to provide
the oily naphthalene 7 (0.20 g, 75%); m=z: 214 (C15H18O, Mþ), 199 (Mþ-
CH3), 184 (Mþ-CH2O); NMR 1H d 1.31 (2d, 6H, -CH(CH3)2,
J ¼ 6.7 Hz), 2.62 (s, 3H, C5-CH3), 3.95 (s, 3H, OCH3), 4.46 (sept.
1H, J ¼ 7.1 Hz), 6.88 (d, 1H, ArH, J ¼ 7.6 Hz), 7.25 (d, 1H, ArH,
J ¼ 7.4 Hz), 7.34 (d, 1H, ArH, J ¼ 7.4 Hz), 7.39 (t, 1H, ArH, J ¼ 8.1 Hz),
Hz), 7.58 (dd, 1H, ArH, J ¼ 8.4 Hz, J ¼ 1.0 Hz) ppm; NMR 13C d: 20.40,
24.83, 30.87, 55.34, 105.73, 117.53, 122.37, 124.15, 125.06, 127.04, 131.57,
135.22, 144.55, 158.19 ppm.

2266
P. S. P. Ng and A. K. Banerjee
A solution of hydrobromic acid 48% (11 ml) was added slowly to a
stirred solution of naphthalene 7 (0.13 g, 0.61 mmol) in acetic acid
(2 ml) at room temperature and then was refluxed for 1 h. The reaction
mixture was diluted with water and extracted with ether. The extracts
were washed with water and NaHCO3 (5%), dried, evaporated, and chro-
matograhed (hexane) to yield 8 (0.11 g, 91%) as a colorless oil. m=z: 200
(C14H16O, Mþ), 185 (Mþ-CH3), 157 (Mþ-C3H7); NMR 1H d: 1.34 (d, 6H,
-CH(CH3)2, J ¼ 6.9 Hz), 2.67 (s, 3H, CH3), 3.05 (sept., 1H, -CH(CH3)2,
J ¼ 6.9 Hz), 5.37 (s, 1H, OH), 6.80 (d, 1H, ArH, J ¼ 7.4 Hz), 7.25 (d,
1H, ArH, J ¼ 7.4 Hz), 7.28 (dd, 1H, ArH, J ¼ 7.4 Hz, J ¼ 8.3 Hz), 7.53
(d, 1H, ArH, J ¼ 8.5 Hz), 7.86 (s, 1H, ArH) ppm; NMR 13C d: 19.91,
23.97, 34.43, 108.62, 115.81, 116.86, 124.52, 124.74, 127.15, 132.69,
134.14, 145.47, 151.53 ppm. Anal. calcd. for C14H16O: C, 83.96; H,
8.05. Found: C, 84.18; H, 8.17.
1-Hydroxy-8-isopropyl-5-methylnaphtalene-2-carbaldehyde 9
To napthol 8 (0.08 g, 0.4 mmol) dissolved in dry tetrahydrofuran (15 ml)
under nitrogen, magnesium chloride (0.076 g, 0.8 mmol), triethylamine
(0.12 ml, 0.8 mmol), and paraformaldehyde (0.036 g, 1.2 mmol) were
added and heated under reflux for 4 h. The reaction mixture was cooled
to room temperature, acidified with hydrochloric acid (1 N), and
extracted with CH2Cl2. The organic phase was washed with NaHCO3
(5%), dried, concentrated, and chromatographed (hexane) to obtain
aldehyde 9, pale yellow oil(0.06 g, 65%). nmax (KBr) 1643.28 cmꢂ1
(CO); m=z: 228 (C15H16O2, Mþ), 213 (Mþ-CH3), 185 (Mþ-C3H7), 170
1
(Mþ-2COH); NMR H d: 1.33 (d, 6H, -CH(CH3)2, J ¼ 6.9 Hz), 2.65 (s,
3H, CH3), 3.05 [sept. 1H, -CH(CH3)2, J ¼ 6.9 Hz], 7.40 (s, 1H, ArH),
7.44 (d, 1H, ArH, J ¼ 8.7 Hz), 7.47 (d, 1H, ArH, J ¼ 8.0 Hz), 8.12 (s,
1H, ArH), 9.95 (s, 1H, CHO), 12.58 (s, 1H, OH) ppm; NMR 13C d:
19.68, 23.84, 34.25, 114.10, 115.65, 118.58, 124.74, 125.50, 131.38,
134.20, 135.33, 146.55, 161.87, 196.41 ppm. Anal. calcd. for C15H16O2:
C, 78.92; H, 7.06. Found: C, 79.18; H, 7.21.
( )-Cis-5-hydroxycalamenene 1
A solution of the aldehyde 9 (0.06 g, 0.26 mmol) in ethyl acetate (25 ml)
was stirred overnight with palladium-charcoal (10%, 0.03 g) under
hydrogen at 500 psi. Removal of catalyst by filtration and evaporation
of the solvent gave a residue, which was chromatographed (hexane=ether
ether 9:1) to obtain (ꢀ)-cis-hydroxycalamenene 1 as viscous liquid
(0.04 g, 72%). nmax (KBr) 3450 cmꢂ1 (OH); m=z: 218 (C15H22O, Mþ),

Total Synthesis of ( )-Cis-5-Hydroxycalamenene
2267
203 (Mþ-CH3), 175 [Mþ-CH(CH3)2], 147 [Mþ-CH(CH3)2-CO]; NMR 1H
d: 0.97 (2d, 6H, -CH(CH3)2, J ¼ 6.7 Hz), 1.28 (d, 3H, CH3, J ¼ 6.8 Hz),
1.5–1.7 (m. 4H), 1.8–1.9 [m, 1H, -CH(CH3)2], 2.20 (s, 3H, CH3), 2.7–2.8
(m, 2H), 4.60 (s, 1H, OH), 6.81 (d, 1H, C8-H, J ¼ 7.9 Hz), 6.92 (d, 1H,
C7-H, J ¼ 7.9 Hz) ppm; [lit.[1,10] 0.91 (d, 3H), 0.94 (d, 3H), 1.29 (d,
3H), 1.6 (m, 2H), 1.8 (m, 2H), 1.97 (m, 1H), 2.18 (s, 3H), 2.8 (m, 2H),
4.59 (s, 1H, OH), 6.72 (1H, JAB ¼ 8 Hz), 6.92 (d, 1H, JAB ¼ 8 Hz)
ppm]; NMR 13C d: 15.59, 19.51, 19.61, 21.71, 27.30, 32.66, 33.77,
36.26, 40.11, 118.41, 119.60, 122.84, 127.60, 141.18, 151.37 ppm. Anal.
calcd. for C15H22O: C, 82.51; H, 10.16. Found: C, 82.73; H, 10.31.
ACKNOWLEDGMENT
We thank LOCTI for partial financial support.
REFERENCES
1. Andersen, N. H.; Bissonette, P.; Liu, C. B.; Shunk, B.; Ohta, Y.; Tseng, C. L.;
Moore, A.; Huneck, S. Sesquiterpenes of nine European liverworts from the
genera Anastrepta, Bazzania, Jungermannia, Lepidozia, and Scapania. Phyto-
chemistry 1977, 16, 1731.
2. Konecny, K.; Streibl, M.; Vasickova, S.; Budesinsky, M.; Saman, D.;
Ubik, K.; Herout, V. Constituents of the liverwort Bazzania trilobata of
Czech origin. Coll. Czechoslovak Chem. Commun. 1985, 50, 80–93.
3. Tanaka, J.; Adachi, K. Studies on aromatic sesquiterpenes, V: Synthesis
of Xanthorrhizol and cyclization of its intermediate. Nippon Kagaku
Kaishi 1983, 1505.
4. Rimpler, H.; Kochendoerfer, L.; Hansel, R. Xanthorrhizol, A new sesquiter-
pene from Curcuma xanthorrhiza. Z. Naturforsch 1970, 25B, 995.
5. Zhong, R.; Zhang, Z.; Wang, Y.; Zeng, Q.; Peng, H. Chemical composition
and antioxidant components of essential oils from leaves, bark and root of
Myrica rubra. Linchan Huaxue Yu Gongye 2006, 26, 1–5.
6. Nagashima, F.; Momosaki, S.; Watanabe, Y.; Takaoka, S.; Huneck, S.;
Asakawa, Y. Sesquiterpenoids from the liverworts Bazzania trilobata and
Porella canariensis. Phytochemistry 1996, 42, 1361–1366.
7. Zhong, H.; Zhang, Z.; Wang, Y.; Xiao, Z.; Zeng, Q.; Peng, H. Chemical
component identification and antioxidant activity of essential oil of Myrica
rubra leaves. Huanan Ligong Daxue Xuebao Ziran Kexueban 2006, 34, 49–53.
8. Scher, J. M.; Speakman, J.; Zapp, J.; Becker, H. Bioactivity guided isolation
of antifungal compounds from the liverwort Bazzania trilobata (L.)
S. F. Gray. Phytochemistry 2004, 65, 2583–2588.
9. Sangaiah, R.; Krishna Rao, G. S. Studies in terpenoides, part LV: Synthesis
of 5-hydroxycalamenene, a phenolic sesquiterpeno from Bazzania tricrenata.
Ind. J. Chem. Sect. B. Org. Chem. Includ. Med. Chem. 1982, 21B, 13–15.

2268
P. S. P. Ng and A. K. Banerjee
10. Tanaka, J.; Adachi, K. Studies on aromatic sesquiterpenes, XII: Synthesis
of (ꢀ)-cis-5-hydroxycalamenene. Bull. Chem. Soc. Jpn. 1990, 63, 272–274.
11. Poon, P. S.; Banerjee, A. K. Alternative procedure for the synthesis of
Mansonone F and Biflorin precursor. Nat. Prod. Res. 2006, 20, 629–635.
12. Burnham, J. W.; Duncan, W.; Eisenbraun, E. J. Effects of allylic substituents
in the chromic acid oxidation of tetralins. J. Org. Chem. 1974, 39, 1416–1420.
13. Silvestre, S. M.; Salvador, J. A. Allylic and benzylic oxidation reactions with
sodium chlorite. Tetrahedron 2007, 63, 2439–2445.
14. Corey, E. J.; Suggs, J. W. Pyridinium chlorochromate: Efficient reagent
for oxidation of primary and secondary alcohols to carbonyl compounds.
Tetrahedron Lett. 1975, 2647.
15. Chdambaram, N.; Chandrasekaran, S. Tert-butyl hydroperoxide-pyridinium
dichromate: A convenient reagent system for allylic and benzylic oxidations.
J. Org. Chem. 1987, 52, 5048.
16. Hansen, T. V.; Skattelbol, L. One pot synthesis of substituted catechols
from the corresponding phenols. Tetrahedron Lett. 2005, 46, 3357.