Total synthesis of achlisocoumarins I-II from Achlys triphylla

Article abstract of DOI:10.1016/j.tet.2014.01.009

A concise and efficient total synthesis of achlisocoumarin I-II has been completed featuring a construction of the isocoumarin skeleton in a single step and the geranyl coupling with bromoarene ring at -10 C exclusive of any chelating ligand.

Full text of DOI:10.1016/j.tet.2014.01.009

Accepted Manuscript
Total Synthesis of Achlisocoumarins I-II from Achyls triphylla
Aamer Saeed, Parvez Mahesar
PII:
S0040-4020(14)00025-8
10.1016/j.tet.2014.01.009
TET 25183
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 30 September 2013
Revised Date: 22 December 2013
Accepted Date: 6 January 2014
Please cite this article as: Saeed A, Mahesar P, Total Synthesis of Achlisocoumarins I-II from Achyls
triphylla, Tetrahedron (2014), doi: 10.1016/j.tet.2014.01.009.
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Total Synthesis of Achlisocoumarins I-II from Achyls triphylla
Aamer Saeed* and Parvez Mahesar
*Email: asaeed@qau.edu.pk
Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan.

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Total Synthesis of Achlisocoumarins I-II from Achyls triphylla
Aamer Saeed and Parvez Mahesar
Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan.
Abstract:
A concise and efficient total synthesis of achlisocoumarin I-II has been completed featuring a
construction of the isocoumarin skeleton in a single step and the geranyl coupling with
bromoarene ring at -10 °C exclusive of any chelating ligand.
Keywords:
Achlisocoumarin I-II, Achlys triphylla, isocoumarin
1. Introduction.
Achlys triphylla (berberidaceae), also called vanilla leaf, deer's foot or sweet after death, is an
erect perennial plant that sprouts from a creeping rhizome. The dried plants are strongly
aromatic and are used as an air freshener and mosquito repellent.1 Mizonu and co-workers
isolated thee phenolic isocoumarin derivatives from the underground parts of Achlys triphylla
named as achlisocoumarin I (E)-3-(4-hydroxyphenethyl)-7-(3,7-dimethylocta-2,6-dienyl)-6,8-
dihydroxyisocoumarin) (1), achlisocoumarin II 3-((E)-4-hydroxystyryl)-7-((E)-3,7-
dimethylocta-2,6-dienyl)-6,8-dihydroxyisocoumarin (2) and achlisocoumarin III (E)-3-(3,4-
dihydroxystyryl)-6,8-6,8-dihydroxyisocoumarin respectively. Compounds I and II are the first
examples of isocoumarin scaffold having a 7-geranyl substituent.2 Few years later, another
Email: asaeed@qau.edu.pk., aamersaeed@yahoo.comTel +92-51-9064-2128; Fax:
+92-51-9064-2241

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isocoumarin derivative achlisocoumarin IV (E)-6,8-dihydroxy-3-(2-(8-hydroxy-2-methyl-2-
(4-methylpent-3-enyl)-2H-chomen-5-yl)vinyl)isocoumarin was isolated by Iinuma et.al3
4
Isocoumarins are physiologically important secondary metabolites such as hiburipyranone,
5
6
8
9
ochatoxin A, 185322, bacilosarcin B,7 paraphaeosphaerins and NM-3 the synthetic
analogue of cytogenin.10
The excellent biological activities coupled with simple structure have attracted the attention of
many synthetic groups towards the total synthesis of this class of natural products. Different
11
strategies employed include metal catalyzed domino reaction,
iron(III) catalyzed
cyclization of 2-alkynylaryl esters,12 Sonogashira coupling of iodobenzoic acid esters and
subsequent cyclization,13 Cu(I)-catalyzed intramolecular sequential C–C coupling, and
rearrangement of 1-(2-halophenyl)-1,3-diones,14 tandem cyclization of halo benzoic acid ester
catalyzed by copper,15 Ugi multicomponent reaction,16 transition metal free arylation and
17
18
cyclization, rhodium catalyzed oxidative coupling of benzoic acids and alkynes, solid
19
20
phase synthesis,
heterocyclic ketene with dihydroxy 1,3-dione
and ligandless Pd-
catalyzed oxidative coupling of benzoic acids and vinylarenes. 21
To the best of our knowledge there has been no previous report on the total synthesis of
achlisocoumarin I and II. The only related synthesis is that of 3-(4-methoxyphenethyl)-6,8-
dimethoxyisocoumarin by Ohta et. al involving ortho-lithiation of corresponding N,N'-
diethyl-2-phenacylbenzamide.22
2. Results and discussion
The retrosynthetic analysis shown in Scheme 1 provides a general strategy for easy
access to the achlisocoumarins I & II through a reaction sequence involving carbon-carbon
coupling of methyl protected target molecule via metal exchange of isocoumarin 11 or 13
followed by nucleophilic substitution with geranyl bromide. The isocoumarin skeleton can be
constructed by condensation of homopthalic acid 10 with suitable esters in a single step. The

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homopthalic acid 10 is obtained from phenylacetic acid 7 via formylation and oxidation
sequence. The latter is accessible from 4-bromo-3,5-dihydroxybenzoic acid by the standard
homologation sequence.
O
OH
O
HO
O
O
O
O
13
OH
O
1 or 2
C-C
O
C-C
C-O
O
O
O
COOH
H
FGI
COOH
OH
11 or 13
O
Br
Br
Br
O
O
+
O
O
O
O
10
O
+
Vilsmeier
formylation
Cl
C-C
Br
O
O
HO
Br
COOH
COOH
Br
O
3
OH
Scheme 1 Retrosynthetic analysis of achlisocoumarins I and II
To achieve the destination molecules 1 and 2, we planned to initiate from
commercially available starting material 4-bromo-3,5-dihydroxybenzoic acid 3 to afford the
4-bromo-3,5-dimethoxyhomophthalic acid (10), as the key intermediate according to the route
outlined in the Scheme 2. Thus, the free hydroxyls as well as the carboxylic function in acid 3
were protected by treating with dimethyl sulfate (DMS) in the presence of K2CO3 in aprotic
solvent to afford the ester 4 in high yield, 23 which upon lithium aluminum hydride reduction
furnished the benzyl alcohol 5 in good yield. 24 The primary alcoholic function was converted
to benzyl nitrile by two successive nucleophilic substitutions with PBr3 and KCN in excellent
yields. 25-26 Hydrolysis of nitrile under basic conditions lead to the formation of corresponding
phenylacetic acid 7 in good yield. 27

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Next the methyl ester of phenylacetic acid 7 was subjected to the Vilsmeier-Haack
28
formylation. Thus, reaction with DMF/POCl3 adduct at 55 °C afforded the formyl ester
8
which was oxidized to the acid 9 using hydroxylamine hydrochloride, 30% H2O2 and 37%
29
HCl in acetonitrile to furnish the product in high yield.
The saponification of ester 9
furnished the desired homopthalic acid 10 in high yield.30
Cyclocondensation of the homopthalic acid 10 with methyl 3-(4-methoxyphenyl)
propanoate and (E)-methyl 3-(4-methoxyphenyl)acrylate separately at elevated temperature
afforded the entire bromoisocoumarin framework 11 and 12 respectively. The significance of
this transformation is that it ended up with whole carbon skeleton in excellent yields in a
single step 31 and is the first application of such condensation of esters with homopthalic acid
in the total synthesis of natural isocoumarins (Scheme 3).

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After having successful isocoumarin formation, the next step ahead was coupling reaction of
geranyl bromide with bromoisocoumarins to afford products 13 and 14 respectively. To this
end, the reaction between isocoumarin 11 and geranyl bromide was chosen for the
optimization of conditions. The different reaction conditions employed for optimization for
this coupling are listed in Table 1. In this investigation different conditions of solvents,
temperature and additives were employed. Consequently the use of tetramethylethylene
diamine (TMEDA) as a chelating agent to trap the metal to generate the anion at lower
concentration followed by coupling with geranyl bromide, was found unsatisfactory due to
poor yield of the products. Combination of TMEDA alongwith CuI to enhance the coupling
activity lead to the self-coupling product instead of the desired hetero coupled product. Using
CuI exclusive of TMEDA the results were still unacceptable for this transformation (entries 1-
7). The best conditions for the coupling protocol were found to be the use of neat
n-butyllithium in dry THF at -10 °C (entry 10).
Table 1 Optimization of coupling reaction.

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Entry Conditions
n-BuLi, TMEDA, -78 °C, ether
n-BuLi, TMEDA, CuI,-78 °C, ether
Yield (%)
1
2
3
4
5
6
7
8
9
10
40
55
NR
42
58
33
62
70
80
80
n-BuLi, CuI, -78 °C, ether
n-BuLi, -78 °C, ether
n-BuLi, TMEDA, -78 °C,THF
n-BuLi, TMEDA, CuI,-78 °C,THF
n-BuLi, CuI, -78 °C, THF
n-BuLi, -78 °C, THF
n-BuLi, -40 °C, THF
n-BuLi, -10 °C, THF
The bromoisocoumarins 11 and 12 were individually subjected to our optimized coupling
conditions which lead to the formation of desired products 13 and 14 in good yields (scheme
4).

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Finally the demethylation was carried out to divulge the title compounds 1 & 2
respectively. The complete cleavage of O-methyl ethers in compound 13 was achieved by
treating with ethanethiol / anhydrous aluminum chloride in dry dichloromethane to unveil the
title compound 1 in good yields.32 In order to evade the malodorous ethanethiol, in case of 14
the use of methionine as sulfur nucleophile and methansulfonic acid as solvent at room
temperature 33 was preferred to give the product 2 in excellent yield (Scheme 5).
3. Conclusion
We have accomplished the first total syntheses of naturally occurring achlisocoumarins I-II
starting from 4-bromo-3,5-dihydroxybenzoic acid via 4-bromo-3,5-dimethoxyhomophthalic
acid as the key intermediate. Significant features of the synthesis include the first application
of the direct condensation of esters with homopthalic acid to afford complete isocoumarin
skeleton and the geranyl coupling with bromoarene ring at -10 °C without any chelating
ligand.
4. Experimental Section
4.1. General

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All reactions were performed under nitrogen in oven-dried or flame-dried glassware using dry
solvents and standard syringe techniques. All reagents were of commercial quality purchased
from Sigma-Aldrich or Merck. Melting points were recorded using a digital Gallenkamp
(SANYO) model MPD.BM 3.5 apparatus and are uncorrected. 1H NMR and 13C NMR spectra
were determined in CDCl3 solution at 300 and 75.5 MHz respectivelhy using a Bruker AM-
300 spectrophotometer. All chemical shifts (δ) were referenced to solvent peak (for 1H NMR,
the residual solvent peak at 7.28 ppm and for 13C NMR at 77.0 ppm respectively). FTIR
spectra were recorded on an a Bio-Rad-Excalibur Series Mode FTS 3000 MX
spectrophotometer. Mass Spectra (EI, 70eV) were taken on a GC-MS, Agilent technologies
6890N with an inert mass selective detector 5973 mass spectrometer and elemental analyses
were conducted using a LECO-183 CHNS analyzer. Thin layer chomatography (TLC) was
conducted on 0.25 mm precoated silica gel plates (60 F254, Merck). Purification was carried
out either with silica gel column chromatography or preparative thin layer chomatography
using petroleum ether / AcOEt (7:3) as eluent. Visualization of chomatograms was made with
UV at 365 and 254 nm. Rf values were calculated using the solvent system petroleum ether
AcOEt (7:3).
4.1.2 Methyl 4-bromo-3,5-dimethoxybenzoate (4).
To the stirred solution of 4-bromo-3,5-dihydroxybenzoic acid (3) 24.0 g, 0.103 mol) in
dry acetone (100 mL), K2CO3 (20.0g, 0.145 mol) and dimethyl sulfate (20 mL, 0.309 mol)
was added with caution. The reaction mixture was refluxed for 24 h. On completion of
reaction (TLC control) the reaction mixture was filtered off and the filtrate was concentrated
in vacuo. Recrystallization from ethanol afforded methyl 4-bromo-3,5-dimethoxybenzoate 4
as colourless prisms. (24.5g, 92 %) Rf = 0.65; Mp 124-126 oC (lit34b 100-102 oC) (νmax (KBr):
1
1723, 1601, 1588 (C=C) cm–1. H NMR (300 MHz, CDCl3) δ 6.72 (2H, s, H-2, H-6), 3.78
(3H, s, COOCH3), 3.62 (6H, s, OCH3) ppm. 13CNMR δ (CDCl3): 179.2 (C=O), 157.7 (C-3,5),

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134.5 (C-1), 125.3 (C-4), 113.2 (C-2,6), 58.3 (COCH3), 63.2 (OCH3) ppm. Anal. Calcd for
C10H11BrO4: C, 43.44; H, 4.02; Found: C, 43.32; H, 4.01; GC-MS m/z 273.9, 275.9.
4.1.3 4-Bromo-3,5-dimethoxybenzyl alcohol (5).
A solution of LiAlH4 (4.43g, 0.12 mol) in freshly distilled dry THF (45 mL) was added drop
wise to a stirred solution of ester 4 (5.48 g, 0.02 mol) in THF (80 mL). The reaction mixture
was stirred at 0 °C for 15 min, left out to reach the ambient conditions and stirred for 8 h. On
completion the reaction mixture was treated with a saturated ammonium chloride solution
(140 mL), stirred for 1 h, acidified with dil. hydrochloric acid and extracted with ethyl acetate
(3 ×25 mL). The extract was dried, evaporated and product was recrystallized with petroleum
ether to afford 4-bromo-3,5-dimethoxybenzyl alcohol 5 as colourless prisms. (4.42g, 90 %) Rf
o
= 0.35; Mp 96-97 C (lit34a 100-102 °C); IR (KBr) νmax: 3362 (O-H), 3024 (C=C-H), 1574
(C=C) cm–1; 1H NMR (300 MHz, CDCl3) δ 6.50 (2H, s, H-2, H-6), 4.57 (2H, s, ArCH2), 3.75
(6H, s, OCH3), 2.48 (1H, s, OH) ppm. 13CNMR δ (CDCl3): 158.3 (C-3, 5), 142.7 (C-1), 121.7
(C-4), 112.5 (C-2, 6), 63.3 (OCH3), 62.0 (OCH3), 42.1 (CH2) ppm. Anal. Calcd for
C9H11BrO3: C, 43.70; H, 4.48; Found: C, 43.70; H, 4.24; GC-MS m/z 245.9, 247.9.
4.1.4 4-Bromo-3,5-dimethoxybenzyl bromide.
Phosphorus tribromide (7.44 g, 2.60 mL, 0.027 mol) was added to a stirred solution of 3,5-
dimethoxybenzyl alcohol (5) (6.64 g, 0.027 mol) in dry benzene (45-50 mL) and the reaction
mixture was stirred for 4 h. The reaction mixture was then poured into ice cold water, the
organic layer was separated, dried and evaporated to dryness. Recrystallization from
petroleum ether afforded 4-bromo-3,5-dimethoxybenzyl bromide as colourless prisms.
o
1
(7.29g 88%) Rf = 0.6; Mp 79-80 C; IR (KBr) νmax: 3018 (C=C-H), 1575 (C=C) cm–1; H
NMR (300 MHz, CDCl3) δ 6.55 (2H, s, H-2, H-6), 4.45 (2H, s, ArCH2), 3.81 (6H, s, OCH3)
13
ppm. CNMR δ (CDCl3): 158.3 (C-3,5), 139.3 (C-1), 158.3 (C-3,5), 116.7 (C-4), 107.1 (C-

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2,6), 62.0 (OCH3), 39.9 (CH2) ppm. Anal. Calcd for C9H10Br2O2: C, 34.87; H, 3.25; Found:
C, 34.55; H, 3.12; GC-MS m/z 307.9, 309.9
4.1.5 4-Bromo-3,5-dimethoxybenzyl cyanide (6).
4-Bromo-3,5-dimethoxybenzyl bromide (10.1 g, 0.033 mol) was dissolved in a mixture of
ethanol (150 mL) and water (150 mL) and potassium cyanide (2.8g, 0.05mol) was added
slowly and resulting mixture was refluxed for 2 h. On completion, the reaction mixture was
poured into ice-cold water and extracted with ethyl acetate (3× 50 mL). The extract was dried
and rotary evaporated to afford the 4-bromo-3,5-dimethoxybenzyl cyanide (6), recrystallized
from petroleum ether as colourless prisms. (7.1g, 85%) Rf = 0.4; Mp 120-121 oC (lit34a. 125-
1
126 oC); IR (KBr) νmax: 3015 (C=C-H), 2267 (C≡N), 1577 (C=C) cm-1; H NMR (300 MHz,
13
CDCl3) δ 6.43 (2H, s, H-2, H-6), 3.78 (6H, s, OCH3) 3.65 (2H, s, ArCH2) ppm. CNMR δ
(CDCl3): 137.7 (C-1), 158.3 (C-3,5), 121.3 (CN), 115.8 (C-4), 110.4 (C-2,6), 63.4 (OCH3)
39.9 (CH2) ppm. Anal. Calcd for C10H10BrNO2: C, 46.90; H, 3.94; N, 5.47; Found: C, 46.65;
H, 3.83; N, 5.23; GC-MS m/z 254.9, 256.9
4.1.6 4-Bromo-3,5-dimethoxyphenylacetic acid (7).
4-Bromo-3,5-dimethoxybenzyl cyanide (6) (2.65 g, 0.0104 mol) was dissolved with stirring in
a mixture of water (7.5 mL), dioxane (10 mL) and methanol (10 mL). Aqueous KOH (6.8g in
5mL H2O) was added and the mixture was refluxed for 48 h. After the completion of reaction,
the mixture was poured into ice cold water and then extracted with ethyl acetate (20 mL). The
extract was discarded and aqueous layer was acidified with dilute HCl. Precipitates were
filtered out and recrystallized from ethanol to afford 4-bromo-3,5-dimethoxyphenyl acetic
acid (7) as light brown solid. (2.42g 85 %) Rf = 0.4; Mp 132-133 oC; IR (KBr) νmax: 3234 (O-
H), 3010 (C=C-H), 1706 (carboxylic C=O), 1573 (C=C) cm–1; 1H NMR (300 MHz, CDCl3) δ
3.58 (2H, s, ArCH2), 3.77 (6H, s, OCH3), 6.44 (2H, s, H-2, H-6), 11.41 (1H, s, COOH)

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ppm.13CNMR δ (CDCl3): 176.5 (C=O), 157.4 (C-3,5), 135.1 (C-1), 116.3 (C-4), 106.5 (C-
2,6), 63.0 (OCH3), 44.3 (CH2), ppm. Anal. Calcd for C10H11BrO4: C, 43.66; H, 4.03; Found:
C, 43.42; H, 3.95; GC-MS m/z 273.9, 275.9
Methyl 4-Bromo-3,5-dimethoxyphenyl acetate.
Compound (7) (3.01 g, 0.011 mol) in dry methanol (125 mL) was treated with conc. H2SO4 (1
mL) and the reaction mixture was refluxed for 8 h. After completion, the reaction mixture was
concentrated to 55 mL and extracted with ethyl acetate (2x50 mL). The extract was washed
with saturated brine, dried and concentrated. The crude oil was vacuum distilled to afford
methyl 4-bromo-3,5-dimethoxyphenyl acetate as yellow oil. (2.4g, 78 %) Rf = 0.8; Mp 43-44
1
°C; IR (KBr) νmax: 3022 (C=C-H), 1731 (ester C=O), 1582 (C=C), 1133 (C-O) cm–1 ; H
NMR (300 MHz, CDCl3) δ 6.22 (2H, s, ArH), 3.74 (6H, s, OCH3), 3.65 (3H, s, COCH3) ppm.
13CNMR δ (CDCl3): 171.4 (C=O), 158.2 (C-2,5), 130.7 (C-1), 113.0 (C-4), 101.8 (C-2,6),
62.3 (OCH3), 52.6 (COCH3), 42.3 (CH2) ppm. Anal. Calcd for C11H13BrO4: C, 45.70; H, 4.53;
Found: C, 45.60; H, 4.31; GC-MS GC-MS m/z 288.10
4.1.7 Methyl 2-(4-bromo-2-formyl-3,5-dimethoxyphenyl)acetate (8).
Freshly distilled phosphorous oxychloride (1.62 g, 0.0105 mol) was added drop wise to the
stirred solution of methyl 4-bromo-3,5-dimethoxyphenyl acetate (2.60g, 0.009 mol) in dry
DMF (15mL) at 55 °C. The reaction mixture was heated to 100°C for 2 h cooled to room
temperature and stirred overnight. Then the reaction mixture was poured into an aqueous
solution of sodium acetate (10%, 10 mL) and shaked vigorously to afford formyl acetate (8)
as yellow precipitates, recrystallized from ethanol. (2.18g, 77 %) Rf = 0.45; Mp 56-57 °C; IR
(KBr) νmax: 3032 (C=C-H), 1725 (ester C=O), 1685 (aldehyde C=O), 1568 (C=C), 1033 (C-
O) cm–1; 1H NMR (300 MHz, CDCl3) δ 10.23 (1H, s, CHO), 6.24 (1H, s, Ar), 3.78 (6H, s,
OCH3), 3.62 (3H, s, COCH3), 3.43 (2H, s, ArCH2) ppm. 13CNMR δ (CDCl3): 196.6

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(Aldehydic C=O), 170.8 (C=O), 154.6 (C-5), 159.8 (C-3), 149.8 (C-1), 123.8 (C-2), 115.3 (C-
4), 108.2 (C-6), 63.5 (OCH3), 55.8 (COCH3), 42.7 (CH2) ppm. Anal. Calcd for C12H13BrO5:
C, 45.45; H, 4.13; Found: C, 45.31; H, 4.01; GC-MS m/z 315.9, 317.9
4.1.8 3-Bromo-2,4-dimethoxy-6-(2-methoxy-2-oxoethyl)benzoic acid (9).
A stirred solution of 4-bromo-3,5-dimethoxy-2-oxophenyl acetate (8) (3.15g 10 mmol),
hydroxylamine hydrochloride (1.75 g, 25 mmol), 30% H2O2 (50 mmol), 37% HCl (30 mmol)
in acetonitrile (50 mL) was refluxed at 80°C for 5 h. On completion of reaction the excess
hydrogen peroxide was deactivated by the addition of saturated aqueous Na2S2O3 (300 mL).
The organic layer was extracted with ethyl acetate (3×50 mL) dried, concentrated and the
residue was purified on a silica gel column using n-hexane/ethyl acetate (80∶20) as eluent.
Evaporation of the solvent gave the analytically pure 3-bromo-2,4-dimethoxy-6-(2-methoxy-
2-oxoethyl)benzoic acid (9) (2.49 g, 75 %) Rf = 0.32; IR (KBr) νmax: 3273 (O-H), 3042 (C=C-
H), 1733 (ester C=O), 1717 (carboxylic C=O), 1581 (C=C), 1043 (C-O) cm–1; 1H NMR (300
MHz, CDCl3) δ 11.03 (1H, s, COOH), 6.24 (1H, s, Ar), 3.62 (3H, s, COCH3), 3.78 (6H, s,
OCH3), 3.43 (2H, s, ArCH2) ppm. 13CNMR δ (CDCl3): 170.8 (ester C=O), 168.6 (acid C=O),
159.8 (C-3), 154.6 (C-5), 149.8 (C-1), 123.8 (C-2), 115.3 (C-4), 108.2 (C-6), 63.5 (OCH3),
55.8 (COCH3), 42.7 (CH2) ppm. Anal. Calcd for C12H13BrO6: C, 43.27; H, 3.93; Found: C,
43.01; H, 3.88; GC-MS m/z 331.9, 333.9.
4.1.9 3-Bromo-6-(carboxymethyl)-2,4-dimethoxybenzoic acid (4-Bromo-3,5-dimethoxy
homophthalic acid) (10).
A stirred solution of 3-bromo-2,4-dimethoxy-6-(2-methoxy-2-oxoethyl)benzoic acid (9) (1.74
g, 5.23 mmol) in ethanol (15 mL) was treated with aqueous KOH (5%, 21 mL). The reaction
mixture was refluxed for 1 h and then ethanol was evaporated. The aqueous layer was
acidified with dilute hydrochloric acid to afford crude 4-bromo-3,5-dimethoxyhomophthalic

15
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acid (10), recrystallized from ethyl acetate as brown needles. (1.31g 79%) Rf = 0.25; IR (KBr)
νmax: 3213 (O-H), 3027 (C=C-H), 1727 (carboxylic ArCO), 1718 (carboxylic ArCH2-CO),
1587 (C=C), 1045 (C-O) cm–1; 1H NMR (300 MHz, CDCl3) δ 11.47 (1H, s, COOH), 11.03
(1H, s, COOH), 6.21 (1H, s, –Ar), 3.72 (6H, s, –OCH3), 3.51 (2H, s, ArCH2), 6.21 (1H, s, Ar)
ppm. 13CNMR δ (CDCl3): 205.3 (ArC=O), 171.1 (CH2-C=O), 136.2 (C3, C5), 135.5 (C2),
133.0 (C6), 125.0 (C4), 124.4 (C1), 55.4 (2×OCH3), 39.7 (CH2), ppm. Anal. Calcd for
C11H11BrO6: C, 41.40; H, 3.47; Found: C, 41.22; H, 3.25; GC-MS m/z 317. 9, 319.9, 285.9,
207.0
4.1.10 7-Bromo-6,8-dimethoxy-3-(4-methoxyphenethyl)isocoumarin (11).
A stirred mixture of methyl 3-(4-methoxyphenyl)propanoate (0.73g, 3.38 mmol) and 4-
bromo-3,5-dimethoxyhomophthalic acid (10) (0.62g, 1.97 mmol) was heated under reflux at
an internal temperature of 200 °C for 5 h, under argon. After the completion of reaction, the
heating bath was removed and the reaction was allowed to cool. The reaction mixture was
diluted with ethyl acetate and subjected directly to preparative thin layer chromatography
using petroleum ether and ethyl acetate (7:3) as eluent to afford isocoumarin (11) as brownish
1
semisolid. (0.64g, 78%) Rf 0.5; IR (KBr)
ν
max: 3045, 2940, 1714, 1583 cm–1; H NMR (300
MHz, CDCl3) δ 7.22 (d, J = 7.5 Hz, 2H), 6.90 (s, 1H, H-4), 6.84 (d, J = 7.4 Hz, 2H), 6.15 (s,
1H, H-4), 3.82 (s, 9H 3×OCH3), 2.77–2.03 (m, 4H, Ar). 13C NMR δ 163.7, 160.9, 158.6,
157.0, 151.3, 136.5, 132.5, 128.6, 114.5, 111.9, 110.2, 108.3, 105.5, 60.6, 56.7, 56.0,
37.6,32.8. Anal. Calcd for C20H19BrO5: C, 57.29; H, 4.57; Found: C, 57.07; H, 4.32; GC-MS
m/z 418.2, 339.1, 296.9, 204.9.
4.1.11 (E)-7-Bromo-6,8-dimethoxy-3-(4-methoxystyryl)isocoumarin (12).
A stirred mixture of methyl (E)-3-(4-methoxyphenyl)acrylate (0.73 g, 3.38 mmol) and 6-
(carboxymethyl)-2,4-dimethoxy-3-methylbenzoic acid (10) (0.62 g, 1.97 mmol) was heated
under reflux at an internal temperature of 200 °C for 5 h. After the completion of reaction

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purified in a manner similar to 11 to afford (12) as a brown solid. (0.62g yield 76%) Rf 0.7;
m.p. 70-72 oC; IR (KBr) max: 3045, 2940, 1714, 1583 cm–1; 1H NMR δ 7.65 (d, J = 15.0 Hz,
ν
1H) 7.65 (d, J = 7.5 Hz, 2H), 6.90 (d, J = 6.7 Hz, 2H) 6.69 (s, 1H), 6.34 (d, J = 15.0 Hz, 1H),
13
6.17 (s, 1H), 6.10 (s, 1H), 3.84 (s, 9H). C NMR δ 163.7, 160.8, 160.0, 157.1, 150.3, 136.0,
132.0, 129.3, 1 28.7, 116.9, 114.5, 112.6, 111.4, 109.1, 108.7, 60.6, 56.7, 56.0. Anal. Calcd
for C20H17BrO5: C, 57.57; H, 4.11; Found: C, 57.23; H, 3.98; GC-MS m/z 416.3, 339.1,
296.9, 204.9.
4.1.12 (E)-7-(3,7-Dimethylocta-2,6-dien-1-yl)-6,8-dimethoxy-3-(4-methoxyphenethyl)-1H-
isochromen-1-one (13).
n-Butyllithium (2.5 mL, 2.3M in hexanes) was added dropwise to the stirred solution of
isocoumarin (11) (2.21 g, 5.30 mmol) in THF (20 mL) at –10 °C during 15 min. After an
additional 20 min, geranyl bromide (2.00 g, 9.20 mmol) was added dropwise over 5 min. The
solution was kept cold for 1 h and allowed to warm slowly to room temperature. After 24 h
the reaction was quenched by addition of water, the resulting solution was extracted with
ethyl acetate, and the combined organic extracts were washed with brine. The organic phase
was dried, evaporated in vacuo, and purified by column chromatography (10% ethyl acetate
in hexanes) yielding the corresponding arene (13) (1.65 g, 83%) as a yellow oil. (1.53g, 63%)
Rf 0.58; IR (KBr) ν
max: 3045, 2940, 1714, 1583 cm–1; 1H NMR (300 MHz, CDCl3) δ 7.13 (d,
J = 7.5 Hz, 2H, Ar), 6.78 (s, 1H, H-5), 6.84 (d, J = 7.4 Hz, 2H,Ar), 6.13 (s, 1H, H-4), 5.57 (t,
J = 6.2 Hz, 2H), 5.04 (m, 2H), 3.82 (s, 6H, 2×OMe), 3.75 (s, 3H, OMe), 3.60 (d, J = 6.2 Hz,
2H), 2.77 (t, 2H, J = 6.1 Hz, CH2), 2.24 (t, J = 7.7 Hz, 2H), 2.07 (t, J = 8.0 Hz, 2H), 1.89 (d, J
= 0.6 Hz, 3H), 1.80 (d, J = 0.9 Hz, 6H).13C NMR δ 165.0, 160.9, 158.6, 151.3, 136.1, 135.5,
132.5, 130.9, 128.7, 128.5, 124.5, 123.6, 123.4, 114.7, 114.4, 111.6, 105.7, 105.5, 60.6, 56.7,
56.4, 38.8, 37.6, 32.8, 27.0, 24.8, 17.9, 16.5. Anal. Calcd for C30H36O5: C, 75.60; H, 7.61;
Found: C, 75.31; H, 7.23; GC-MS m/z 476.4, 461.2, 355.1, 334.1, 316.4, 220.2.

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4.1.13 7-((E)-3,7-Dimethylocta-2,6-dien-1-yl)-6,8-dimethoxy-3-((E)-4-methoxystyryl)-1H-
isochromen-1-one (14).
Compound 14 was prepared from 12 according to procedure analogous to that adopted for the
conversion of 11 to 13, as a brown oil. (0.2g, 80%) Rf 0.56; IR (KBr) νmax: 3045, 2940, 1714,
1
1583 cm–1; H NMR (300 MHz, CDCl3) δ 7.28 (d, J = 7.5 Hz, 2H, Ar), 7.21 (d, J = 7.5 Hz,
2H, Ar), 7.03 (d, J = 15.2 Hz, 1H), 6.85 (d, J = 15.2 Hz, 1H), 6.70 (s, 1H, H-5), 6.29 (s, 1H,
H-4), 5.89 (m, 1H), 5.22 (m, 1H), 3.82 (s, 6H, 2×OCH3), 3.82 (s, 6H, 2×OCH3), 3.48 (m, 2H),
2.17 (m, 4H), 1.81 (m, 9H); 13C NMR δ 164.8, 160.8, 160.0, 158.1, 150.3, 136.1, 135.0,
132.0, 131.0, 129.3, 128.7, 124.5, 123.7, 123.4, 116.9, 114.5, 111.4, 110.6, 104.2, 60.6, 56.7,
56.0, 38.8, 27.0, 24.8, 17.9, 16.6. Anal. Calcd for C30H34O5: C, 75.92; H, 7.22; Found: C,
75.72; H, 7.12; GC-MS m/z 476.2, 461.2, 355.134.1, 316.4, 220.2.
4.1.2 (E)-7-(3,7-dimethylocta-2,6-dien-1-yl)-6,8-dihydroxy-3-(4-hydroxyphenethyl)
isocoumarin (1).
The trimethoxy isocoumarin (13) (0.293 g, 0.617 mmol) was dissolved in ethane thiol (2.5
ml) and the solution was cooled to 0 °C. Anhydrous aluminum chloride (0.230 g, 0.187
mmol) was added in thee portions with intervals of 30 min. each. After the addition was
complete, the reaction mixture was stirred further at 0 °C for 1h. The reaction was quenched
with 10 % NaHCO3 and extracted with ethyl acetate; sodium chloride was added to enhance
the layer separation. The combined organic layers were washed once with brine, dried and
concentrated to the target molecule as brownish amorphous solid (1) (0.20 g, 77%), Rf 0.3; IR
(KBr) ν
max: 3425 (OH), 3065, 2925, 1712, 1567 cm–1; 1H NMR (300 MHz, CDCl3) δ 7.01 (d,
J = 7.5 Hz, 2H, Ar), 6.73 (d, J = 7.5 Hz, 2H, Ar), 6.44 (s, 1H, H-5), 6.07 (s, 1H, H-4), 5.44 (t,
J = 6.1 Hz, 1H), 5.25 (t, J = 6.6, 1H), 3.43 (m, 2H, CH3), 3.39 (m, 2H, CH2), 3.35 (m, 2H,
CH2), 2.81 (t, 2H, J = 6.1 Hz, CH2), 2.79 (t, J = 6.2 Hz, 2H, CH2), 1.89 (m, 3H), 1.78 (brs,

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6H, 2×CH3); 13C NMR δ 164.9, 163.7, 159.8, 156.0, 151.3, 136.1, 135.0, 132.0, 131.0, 129.3,
124.5, 123.4, 118.6, 116.8, 105.5, 102.4, 100.8, 38.8, 37.7, 32.8, 27.0, 24.9 , 23.1, 18.0, 16.5.
Anal. Calcd for C27H30O5: C, 74.63; H, 6.96; Found: C,74.52; H, 6.78; GC-MS m/z 434.4,
461.2, 327.1, 287.1, 222.8, 220.2.
4.1.14 7-((E)-3,7-dimethylocta-2,6-dien-1-yl)-6,8-dihydroxy-3-((E)-4-hydroxystyryl)-1H-
isochomen-1-one (2).
The trimethoxy isocoumarin (14) (0.417 g, 0.88 mmol) was dissolved in methansulfonic acid
(1.7 mL) and D,L-methionine (143 mg, 0.96 mmol) was added to the solution under stirring at
room temperature. After 10 h the reaction mixture was diluted with water (10 mL) and
extracted with ethyl acetate (5×30 mL). The combined organic layers were separated, dried
and the solvent evaporated under reduced pressure to afford solid which on preparative thin
layer chromatography on silica gel (benzene-MeOH 14:3) gave the target compound (2) as
sticky brown semisolid. (0.32g, 86%) Rf 0.5; IR (KBr) νmax: 3425 (O-H), 3065, 2925, 1712,
1
1567 cm–1; H NMR δ 7.14 (d, J = 7.5 Hz, 2H, Ar), 7.03 (d, J = 15.2 Hz, 1H-olefinic), 6.89
(d, J = 7.5 Hz, 2H, Ar), 6.69-5.57 (m, 4H, H-4, H-5, H-olefinic), 5.23 (m, 1H), 5.23 (d, J =
6.2 Hz, 2H, CH2), 2.10–1.93 (m, 4H), 1.89-1.79 (brs, 7H, 2×CH3, H-olefin), 1.61 (s, 3H,
CH3); 13C NMR δ 164.0, 163.0,159.7, 159.3, 150.3, 136.1, 135.0, 132.0, 131.0, 130.0, 127.7,
124.5, 123.5, 118.7, 117.0, 116.3, 111.4, 101.5, 100.4, 38.8, 27.0, 24.8, 23.1, 18.0, 16.53.
Anal. Calcd for C27H28O5: C, 74.63; H, 6.96; Found: C, 74.41; H, 6.89; GC-MS m/z 432.1,
326.1, 309.0, 222.8, 220.2.
Acknowledgements
We are grateful for the generous financial support from the Higher Education Commission of
Pakistan under the project No.20-Miscel/R&D/00/3834.
References and notes

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1.
2.
3.
Gilky, H. M.; Dennis, R. J.; In Handbook of Northwestern Plants Oregon State
University Press, 2001; p 161.
Mizuno, M.; Yoshida, S.; Iinuma, M.; Tanaka, T.; Lang, F. A.; Goto, K. Chem.
Pharm. Bull. 1990, 38, 2075.
Iinuma, M.; Tosa, H.; Tanaka, T.; Mizuno, M.; Lang, F. A. J. Nat. Prod. 1993, 56,
1638.
4.
5.
Uchida, K.; Watanabe, H.; Mori, K. Biosci. Biotech. Biochem. 1997, 61, 1564.
Van der Merwe K.J.; Steyn P.S.; Fourie L.; Scott D.B.; Theron J.J. Nature, 1965, 205,
1112.
6.
Kawano, T.; Agata, N.; Kharbanda, S.; Avigan, D.; Kufe, D. Cancer Chemoth. Pharm.
2007, 59, 329.
7.
Azumi, M.; Ogawa, K.; Fujita, T.; Takeshita, M.; Yoshida, R.; Furumai, T.; Igarashi,
Y. Tetrahedron 2008, 64, 6420.
8.
Wijeratne, E. M. K.; Paranagama, P. A.; Gunatilaka, A. A. L. Tetrahedron, 2006, 62,
8439.
9.
Bauta, W. E.; Lovett, D. P.; Cantrell, W. R.; Burke, B. D. J. Org. Chem.2003, 68,
5967.
10.
a) Saeed, A. J. Heterocyclic Chem. 2004, 41, 975. b) Saeed, A. Zeit. Naturforsch. C,
2003, 58C, 691.
11.
12.
Cai, S. J.; Wang, F.; Xi, C. J. J. Org. Chem. 2012, 77, 2331.
Speranca, A.; Godoi, B.; Pinton, S.; Back, D. F.; Menezes, P. H.; Zeni, G. J. Org.
Chem. 2011, 76, 6789.
13.
Roy, S.; Roy, S.; Neuenswander, B.; Hill, D.; Larock, R. C. J. Comb. Chem. 2009, 11,
1128.

20
ACCEPTED MANUSCRIPT
14.
15.
Ge, Z. Y.; Fei, X. D.; Tang, T.; Zhu, Y. M.; Shen, J. K. J. Org. Chem. 2012, 77, 5736.
Fan, X. S.; He, Y.; Cui, L. Y.; Guo, S. H.; Wang, J. J.; Zhang, X. Y. Eur. J. Org.
Chem. 2012, 673.
16.
17.
Faggi, C.; Garcia-Valverde, M.; Marcaccini, S.; Menchi, G. Org. Lett. 2010, 12, 788.
Liu, L.; Hu, J.; Wang, X. C.; Zhong, M. J.; Liu, X. Y.; Yang, S. D.; Liang, Y. M.
Tetrahedron, 2012, 68, 5391.
18.
19.
Ueura, K.; Satoh, T.; Miura, M. J. Org. Chem. 2007, 72, 5362.
Peuchmaur, M.; Lisowski, V.; Gandreuil, C.; Maillard, L. T.; Martinez, J.; Hernandez,
J. F. J. Org. Chem. 2009, 74, 4158.
20.
21.
Yan, S. J.; Chen, Y. L.; Liu, L.; Tang, Y. J.; Lin, J. Tetrahedron Lett. 2011, 52, 465.
Nandi, D.; Ghosh, D.; Chen, S. J.; Kuo, B. C.; Wang, N. M.; Lee, H. M. J. Org. Chem.
2013, 78, 3445.
22.
23.
24.
Ohta, S.; Kamata, Y.; Inagaki, T.; Masuda, Y.; Yamamoto, S.; Yamashita, M.;
Kawasaki, I. Chem. Pharm. Bull. 1993, 41, 1188.
Caille, J. C.; Govindan, C. K.; Junga, H.; Lalonde, J.; Yao, Y. M. Org. Process Res.
Dev. 2002, 6, 471.
Salomaa, P.; Kankaanpera A.; Pihlaja, K., in Patai, S. The Chemistry of the Hydroxyl
Group, Wiley, NY, 1971, pt. 1, pp. 595.
25.
26.
Varma, R. S.; Naicker, K. P. Green Chem. 1999, 1, 247.
Chandrasekhar, B.; Prasad, A. S. R.; Eswaraiah, S.; Venkateswaralu, A. Org. Process
Res. Dev. 2002, 6, 242.
27.
28.
Boesch, H.; Cesco-Cancian, S.; Hecker, L. R.; Hoekstra, W. J.; Justus, M.; Maryanoff,
C. A.; Scott, L.; Shah, R. D.; Solms, G.; Sorgi, K. L.; Stefanick, S. M.; Thurnheer, U.;
Villani, F. J.; Walker, D. G. Org. Process Res. Dev. 2001, 5, 23.
Black, D. S.; Kumar, N.; Wong, L. C. H. Synthesis-Stuttgart 1986, 474.

21
ACCEPTED MANUSCRIPT
29.
30.
31.
Deussen, H. J.; Jeppesen, L.; Scharer, N.; Junager, F.; Bentzen, B.; Weber, B.; Weil,
V.; Mozer, S. J.; Sauerberg, P. Org. Process Res. Dev. 2004, 8, 363.
Burks, J. E.; Espinosa, L.; LaBell, E. S.; McGill, J. M.; Ritter, A. R.; Speakman, J. L.;
Williams, M. Org. Process Res. Dev. 1997, 1, 198.
a) Saeed, A. Helv. Chim. Acta 2003, 86, 377. b) Rama, N. H.; Saeed, A.; Bird, C. W.
Liebigs Ann. 1995, 711. c) Rama, N. H.; Saeed, A.; Bird, C. W. Liebigs Ann. 1995,
711. d) Saeed, A. Nat. Prod. Res. 2013, 27, 1153.
32.
33.
Node, M.; Nishide, K.; Sai, M.; Ichikawa, K.; Fuji, K.; Fujita, E. Chem. Lett. 1979, 97.
Scott, R. W.; Neville, S. N.; Urbina, A.; Camp, D.; Stankovic, N. Org. Process Res.
Dev. 2006, 10, 296.
34.
a) Nichols; D.E.; Dyer, D.C. J. Med. Chem., 1977, 20 (2), 299. (makes reference to
these compounds, but except for melting points no spectral data is reported).
b) Saeed, A.; Qasim, M.; Simpson, J. Acta Crystallograph. C, C69, 2113, 790.