Synthesis of stachybotrin C and all of its stereoisomers: Structure revision

Article abstract of DOI:10.1021/jo401116r

We disclose the first total synthesis of stachybotrin C, a potent neuroprotective natural compound. All of the four stereoisomers have been prepared and fully characterized with the aim to attribute the absolute configuration of the two adjacent stereocenters of the stachybotrin C.

Full text of DOI:10.1021/jo401116r

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Article
Synthesis of Stachybotrin C and all of its stereoisomers. Structure revision.
Maiwenn Jacolot, Mickael Jean, Naresh Tumma, Arnaud
Bondon, Srivari Chandrasekhar, and Pierre van de Weghe
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo401116r • Publication Date (Web): 17 Jun 2013
Downloaded from http://pubs.acs.org on June 17, 2013
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Synthesis of Stachybotrin C and all of its stereoisomers.
Structure revision.
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Maiwenn Jacolot,§ Mickael Jean,§ Naresh Tumma,‡ Arnaud Bondon,$ Srivari Chandrasekhar,‡ Pierre
van de Weghe§*
§Université de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes, Equipe PNSCM,
UFR des Sciences Biologiques et Pharmaceutiques, 2 avenue du Prof Léon Bernard, F-35043 Rennes
‡
Cedex, France, Division of Natural Product Chemistry, Indian Institute of Chemical Technology,
$
Uppal Road, Tarnaka, Hyderabad, 500607, India, UMR CNRS 6290, Equipe SIM, PRISM, Biosit,
Faculté de Médecine, CS 34317, Université de Rennes 1, 35043, Rennes Cedex, France.
pierre.van-de-weghe@univ-rennes1.fr
RECEIVED DATE
OH
Me
OH
Me
Me
Me
Me
Me
initially
O
OH
isolation
Me
Me
O
OH
synthesis
corrected
structure
stachybotrin C
proposed structure
N
N
O
O
(8S*,9S*)
(8S,9R)
HO
HO
We disclose the first total synthesis of stachybotrin C, a potent neuroprotective natural compound. All
of the four stereoisomers have been prepared and fully characterized with the aim to attribute the
absolute configuration of the two adjacent stereocenters of the stachybotrin C.
INTRODUCTION
As recently discussed by R. W. Hoffmann,1 the goal of the natural product synthesis has deeply
changed during the last two centuries. However, among the aims of the total synthesis, the
confirmation of the structure of new isolated compounds remains a strong object of motivation and
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particularly the unambiguously attribution of the relative and absolute configurations of stereogenic
centers.
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9
In 1997, Hanada et al.2 reported the isolation of stachybotrin C 1 (Figure 1) from the culture broths
of Stachybotrys parvispora F4708. These authors also stated some interesting biological properties for
this natural compound since it has exhibited significant neurite outgrowth in PC12 cells and has shown
protecting effects against neuronal damage. Due to its potent neuritogenic properties stachybotrin C 1
has been sought for the treatment of neurodegenerative diseases.3 The structure of 1 has been deduced
by classical spectroscopic analyses and while the relative configuration of the two adjacent
stereocenters has been established by NOESY analyses4 the absolute configurations of the two chiral
centers were not determined. Despite efforts described by Inoue and coll. in 2006 and more recently
by us,5 to our knowledge, no total synthesis has been reported. In this letter, we described the first total
synthesis of 1 and its other stereoisomers in order to confirm the structure and to establish the absolute
configurations of the two chiral centers.
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Figure 1. Proposed structure of stachybotrin C.
25
Me
OH
14
Me
8
7
9
Me
Me
O
OH
1: stachybotrin C
N
O
HO
Our strategy to prepare 1 in its racemic form, has been based upon the retrosynthetic analysis
outlined in Scheme 1 which consists in two key steps: a thermal Claisen transposition6 and a
regioselective epoxidation to form the 3ꢀchromanol moiety.7
Scheme 1. Stachybotrin C retroanalysis.
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O
O
PO
PO
N
R1
Me
N
R1
1
O
OH
regioselective
epoxidation with
remote control
HO
Me R2
R2
B
A
8
9
O
PO
O
R1
PO
N
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N
R1
Claisen
O
C
D
OH
Me R2
R
ESULTS AND DISCUSSIONS
Our first task was to prepare the 2,3ꢀdihydroꢀ1Hꢀisoindolone derivative 3 from commercially
available 3,5ꢀdihydroxybenzoic acid 2 as previously reported (Scheme 2).5b A copperꢀcatalyzed
coupling reaction between the phenol 3 and the carbonate 45b afforded the propargylic ether
intermediate easily converted into the corresponding alkene 5 by hydrogenation in the presence of
Lindlar catalyst. A Claisenꢀtransposition (1,3ꢀshift) mediated under thermal condition in the presence
of a catalytic amount of 3,5ꢀdiꢀtertꢀbutylꢀ4ꢀhydroxytoluene (BHT) gave the prenylated derivative 6 as
a mixture of two unseparable E / Z olefins (in 2:1 ratio) isolated in good yield (80%). The BHT seems
to catalyze the reaction as a Brönsted acid, since in its absence no rearrangement occurred and only the
starting material has been recovered.
Scheme 2. Synthesis of racemic diastereoisomers of stachybotrin C.a
O
O
O
HO
CO2H
MOMO
MOMO
MOMO
OMOM
N
N
R1
N
R1
a
b, c
d
e
OH
OH
O
Me
OH
2
3
5
6
R2
Me
Me
(E / Z = 2 / 1)
Me
Me
O
O
O
MOMO
HO
MOMO
MOMO
N
R1
N
R1
N
R1
+
+
Me
8
9
8
Me OCO2Me
9
R1
R2
=
=
O
O
O
Me
H2CH2C
Me
OMOM
Me
HO
HO
7
8
9
Me
Me
R2 Me
Me R2
R2
(8S*, 9R*)
(8S*, 9S*)
Me
4
50-55%
10-15%
5-10%
aReagents and conditions: a: see ref 5b. b: 4, K2CO3 (2 equiv), KI (2 equiv), CuI (20 mol%), acetone,
reflux, 2 d, 75ꢀ80%. c: H2 (1 atm), Pd Lindlar, EtOAc, rt, 8 h, 90%. d: BHT (10 mol%), xylene, reflux,
6 h, 80%. e: VO(acac)2 (1.5 mol%), TBHP (1.3 equiv), TFA (20 mol%), CH2Cl2, 40 °C, 3 h.
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Next we examined the direct formation of the 3ꢀchromanol using a methodology reported by
Lattanzi and coll.7 For this purpose the alkene 6 has been submitted to oxidative reaction conditions by
the use of a catalytic amount of VO(acac)2 in the presence of tertꢀbutylhydroperoxide (TBHP) and 20
mol% of trifluoroacetic acid (TFA) in methylene chloride under reflux. We were delighted to observe
the formation of the expected 3ꢀchromanol obtained as a mixture of two racemic diastereoisomers 7
and 8 along with a small amount of the 5ꢀexoꢀcyclization product 9. The mass balance of the products
formed confirms the regioselective oxidation of the alkene closer to the aromatic moiety indicating
that the epoxidation occurs via the coordination of the phenol function to the vanadium.8 We also paid
particular attention to an asymmetric epoxidation version of this key step, different reaction conditions
have been evaluated but none of these allowed a regioselective oxidation of the desired olefin.
Initially, we tried to characterize the relative configuration of Cꢀ8 and Cꢀ9 for both diastereoisomers
7 and 8 with the help of NOESY analyses and other NMR sequences. Although we had in hand the
two stereoisomers it was not possible to conclude toward the stereochemical relationship between the
two chiral centers for the major and minor 3ꢀchromanols. In the same time, we focused our efforts to
convert 7 and 8 as benzoic ester derivatives with the aim to obtain crystals suitable for Xꢀray
diffraction analysis. Because no crystal has been obtained, simplified 3ꢀchromanols have been
prepared from the phenol E-109 and Z-1010 as depicted in Scheme 3. After derivatization of trans-11
into the ester 12, crystals were grown by slow evaporation of methanol at room temperature. The
crystal structure11 confirms the trans relative configuration in 12 between the unsaturated side chain
and the alcohol function and therefore that 11 has been isolated as the trans-isomer as reported by
Lattanzi and coll.7,11 By comparison of the 1H and 13C NMR spectra of 7 and 8 with trans-11 and cis-
11, the trans relative configuration has been assigned to the compound 7, while the cis relative
configuration to 8.11
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Scheme 3. Preparation of simplified 3ꢀchromanols.a
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Me
Me
Me
OH
O
a
Me
Me
OR
R = H, trans-11
Me
E-10
b
R = 4-iodobenzoyl-, 12
Me
Me
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Me
OH
O
a
Me
OH
R = H, cis-11
Me
Me
Z-10
aReagents and conditions: a: VO(acac)2 (1.5 mol%), TBHP (1.3 equiv), TFA (20 mol%), CH2Cl2,
40 °C, 3 h, trans-11 60% yield and cis-11 43% yield. b: 4ꢀiodobenzoic acid, DCC, DMAP, CH2Cl2, rt,
12 h, 68% yield. DCC = dicyclohexylcarbodiimide, DMAP = 4ꢀ(dimethylamino)pyridine
Being sure of the relative configuration in each diastereoisomer 7 and 8 we then tackled isolation of
each stereoisomers. To do so, enantiomerically pure (S)ꢀOꢀmethyl mandelic acid 13 was reacted with 7
to provide the pair of diastereomeric esters 14 and 15 as a 1:1 mixture. In a similar way, the compound
8 has been converted into diastereomeric esters 16 and 17 (Scheme 4). Choice of the installation of
this group served the dual purpose of creating a pair of separable diastereoisomers in order to obtain
after cleavage of this function enantiopure stachybotrin C (or stereoisomers), as well as a diagnostic
for assigning the absolute configuration of the stereogenic centers.12
Scheme 4. Synthesis of the stachybotrin C and its stereoisomers.a
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O
O
MOMO
HO
MOMO
N
R1
N
R1
O
O
(8S*,9R*)
(8S*,9S*)
HO
Me R2
R2 Me
7
8
8
9
MeO
CO2H
MeO
CO2H
a
a
Ph
Ph
(S)-13
(S)-13
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O
O
O
O
MOMO
R3O
MOMO
MOMO
R3O
MOMO
N
R1
N
R1
N
R1
+
N
R1
+
O
O
O
O
R3O
R3O
(8S,9R,S)
14
(8R,9S,S)
15
(8S,9S,S)
16
(8R,9R,S)
17
Me R2
Me R2
R2 Me
R2 Me
43%
43%
30%
23%
b
88%
b
99%
b
99%
b
88%
O
O
O
O
MOMO
HO
MOMO
MOMO
MOMO
HO
N
R1
N
R1
N
R1
N
R1
O
O
O
O
(8S,9R)
18
(8R,9S)
19
(8S,9S)
20
(8R,9R)
21
HO
HO
Me R2
Me R2
R2 Me
R2 Me
er = 98:2
er = 96:4
er = 96:4
er = 98:2
c
69%
c
65%
c
67%
c
79%
O
O
O
O
HO
HO
HO
HO
N
R
N
R
N
R
N R
O
O
O
O
(8S,9R)
(8R,9S)
(8S,9S)
(8R,9R)
HO
HO
HO
HO
Me R2
Me R2
R2 Me
R2 Me
22
23
24
25
[α] = -13.0 (c 1.1, MeOH)
[α] = +13.6 (c 1.5, MeOH)
[α] = +27.2 (c 0.47, MeOH)
[α] = -22.4 (c 0.37, MeOH)
mp = 90-92 °C
mp = 96-98 °C
isolated stachybotrin C: [α] = -28.18 (c 0.1, MeOH), mp = 89-92 °C
Me
Me
Me
O
R1
=
R2
=
R3
=
MeO
R = H2CH2C
OH
H2CH2C
OMOM
Ph
aReagents and conditions: a: DCC, DMAP, CH2Cl2, rt, 14 h. b: MeONa, MeOH, rt, 2 h. c: AcCl,
MeOH, rt, 6 h.
After separation, each diastereoisomer has been then subjected to NMR analyses. The assignment of
the absolute configuration was based on the shielding effects of the phenyl ring on identifiable protons
on the 3ꢀchromanol derivatives. According to the model, the hydrogen of the alcohol, the ester
carbonyl and the methoxy group of the Oꢀmethyl mandelate all lie in a plane. For example, when
viewed in this manner for the isomer 14, the Cꢀ25 methyl group observes shielding of protons
proximal to the phenyl group of the ester relative to the chemical shifts of the corresponding protons
of racemic alcohol 7. On the contrary, for the isomer 15, the Cꢀ7 methylene group were shielded while
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the chemical shift of the protons of the Cꢀ25 methyl group remain unchanged (Figure 2). These data
indicate that the absolute configuration of the Cꢀ8 is S for 14 and R for 15.
6
7
Figure 2. Assignment of the absolute configurations on esters 14 and 15.
8
9
δ = 2.8 &
3.0 ppm
δ = 1.3 ppm
OMe
H
OMe
H
H
Me
10
11
12
13
14
15
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H
R
H
H
Ph
Me
R
Ph
H
H
O
O
δ = 1.0 ppm
δ = 2.5 & 2.9 ppm
(-0.3 & -0.1)
(-0.3)
14
15
For the purpose of establishing which synthesized isomer corresponds to the natural stachybotrin C,
the ester moiety was cleaved using sodium methoxide to afford alcohols 18‐21. After isolation of these
products, their enantiomeric purity has been determined by chiral HPLC. The methoxymethylether
have been then cleaved by inꢀsitu formation of HCl affording after purification all the four
stereoisomers of stachybotrin C.
Careful NMR analysis of all isomers and comparison with the H and 13C NMR of the natural
1
stachybotrin C,2 has been carried out.11 The compound 22 possesses all the NMR data and also the
melting point consistent with the natural product. Only the optical rotation differs substantially from
our. Thus, as indicated in the literature,2 the compound 1 having the reported relative configuration
(8S*,9S*) has an optical rotation of ꢀ28.18 (c 0.1, MeOH) whereas the synthesized product 22 has [α]
= ꢀ13.0 (c 1.1, MeOH). The compound 22 has a high enantiomeric purity, as demonstrated above by
chiral HPLC analyses of its precursor 18 (e.r. = 98:2). We believe therefore that the aforementioned
literature value is probably affected by an inedaquate purity of the sample of natural stachybotrin C.
CONCLUSION
In summary, we have demonstrated the validity of the sequence thermal Claisen transposition
followed by a regioselective epoxidation to prepare the stachybotrin C and all of its stereoisomers.
Because 3ꢀchromanol pattern is frequently encountered in the large familly of natural products,
application of this methodology is in progress and will be reported in due course. The present work
further shows that the initially reported relative configuration of the two stereogenic centers has been
misassigned indicating that NMR spectroscopy is not a definitive technique for structure
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determination. This proves that total synthesis still has a crucial role to solve structural elucidation of
natural products.
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EXPERIMENTAL SECTION
7
8
General information. All reagents and solvents were used as purchased from commercial suppliers
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or were purified/dried according to Armarego W. L. F. and Chai C. L. L. (Purification of Laboratory
Chemicals, 6th edition, Elsevier). NMR analyzes were done on a 300 or 500 MHz spectrometer. δ
values are given in parts per million (ppm), coupling constants (J values) are given in Hertz (Hz), and
multiplicity of signals are reported as usual. HRMS analyzes were obtained using a QꢀTOF or a TOFꢀ
Q instrument for ESI. Melting points were took on a hot bench. Chiral HPLC analyzes were performed
using Daicel Chiralpak IA and IC columns. TLC analyzes were carried out using precoated silica gel
60 F254 plates and purifications for columns chromatography using silica gel 60 (70ꢀ200 mesh and 40ꢀ
60 mesh) or using silica gel 60 PF254 for preparative thin layer chromatography. Petroleum ether (PE)
used for purifications was the low boiling point fraction (40ꢀ60 °C). Experimental procedures for
compounds prior to 5 have been given in ref 5b.
6-Methoxymethoxy-2-[2-(4-methoxymethoxyphenyl)ethyl]-4-((E)-1,5,9-trimethyl-1-vinyldeca-
4,8-dienyloxy)-2,3-dihydroisoindol-1-one 5. To a solution of (E)ꢀ4ꢀ(1ꢀethynylꢀ1,5,9ꢀtrimethyldecaꢀ
4,8ꢀdienyloxy)ꢀ6ꢀmethoxymethoxyꢀ2ꢀ[2ꢀ(4ꢀmethoxymethoxyphenyl)ethyl]ꢀ2,3ꢀdihydroꢀisoindolꢀ1ꢀone
(2.29 g, mmol, 1.0 eq.) in EtOAc (100 mL) was added Lindlar Pd (15% w/w, 340 mg) and the
suspension was stirred for 6 h under an atmosphere of H2. Then, the reaction mixture was filtered
through a pad of celite and the filtrate was concentrated under reduce pressure. The residue was
purified by column chromatography on silica gel using CH2Cl2/EtOAc 4/1 as eluent affording 5 as a
pale yellow oil (2.07 g, 90%). 1HꢀNMR (500 MHz, CDCl3): δ 1.48 (s, 3H), 1.57 (s, 3H), 1.61 (s, 3H),
1.69 (s, 3H), 1.82ꢀ1.48 (m, 2H), 2.17ꢀ1.95 (m, 6H), 2.62 (t, J = 7.6, 2H), 3.46 (s, 3H), 3.48 (s, 3H),
3.80 (t, J = 7.8, 2H), 4.15 (d, J = 3.1, 2H), 5.13ꢀ5.08 (m, 2H), 5.14 (s, 2H), 5.30ꢀ5.18 (m, 2H), 6.07
(dd, J = 11.0 and 17.6, 1H), 6.89 (d, J = 1.9, 1H), 6.96 (d, J = 8.4, 2H), 7.11 (d, J = 1.8, 1H), 7.16 (d, J
= 8.4, 2H); 13CꢀNMR (125 MHz, CDCl3): δ 60.8, 61.3, 62.5, 62.6, 63.4, 63.4, 63.7, 63.7, 65.6, 67.1,
67.7, 68.4, 69.4, 71.4, 71.5, 78.4, 81.6, 81.7, 83.9, 85.8, 87.0, 87.4, 89.3, 89.5, 90.0, 90.9, 90.9, 91.4,
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91.6, 92.3, 92.5, 94.4, 96.8, 97.9, 98.4, 101.2; HRMS (ESI) [M+Na]+: calcd for C35H47NO6Na:
600.3301; found: 600.3300.
6
4-Hydroxy-6-methoxymethoxy-2-[2-(4-methoxymethoxyphenyl)ethyl]-5-((2E,6E)-3,7,11-
7
8
9
trimethyldodeca-2,6,10-trienyl)-2,3-dihydroisoindol-1-one
(E)-6
and
4-Hydroxy-6-
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methoxymethoxy-2-[2-(4-methoxymethoxyphenyl)ethyl]-5-((2Z,6E)-3,7,11-trimethyldodeca-
2,6,10-trienyl)-2,3-dihydroisoindol-1-one (Z)-6. To a solution of 5 (2.53 g, 4.38 mmol, 1.0 eq.) in
dry xylene (75 mL), a catalytic amount of BHT was added and the mixture was allowed to stir under
reflux for 6 h. The solvent was then removed under reduced pressure and the residue was purified by
column chromatography on silica gel using Et2O/PE 7/3 as eluent affording a mixture of unseparable
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diastereoisomers 6 in ratio E/Z 2/1 (2.0 g, 80%). (E)-6: HꢀNMR (500 MHz, CDCl3): δ 1.58 (s, 6H),
1.66 (s, 3H), 1.82 (s, 3H), 1.94ꢀ2.29 (m, 8H), 2.90 (t, J = 7.3, 2H), 3.45 (s, 3H), 3.46 (s, 3H), 3.53 (d, J
= 7.0, 2H), 3.80 (t, J = 7.7, 2H), 4.20 (s, 2H), 5.05ꢀ5.10 (m, 2H), 5.12 (s, 2H), 5.20 (s, 2H), 5.23ꢀ5.29
(m, 1H), 6.46 (bs, 1H), 6.93 (d, J = 8.6, 2H), 7.13 (d, J = 8.6, 2H), 7.14 (s, 1H); 13CꢀNMR (125 MHz,
CDCl3): δ 16.0, 16.2, 17.7, 23.0, 23.5, 25.7, 26.3, 26.6, 33.9, 39.6, 39.7, 44.4, 48.0, 55.9, 56.2, 94.5,
94.9, 101.2, 101.3, 116.4, 119.8, 121.2, 121.8, 123.5, 124.3, 129.6, 131.3, 132.0, 132.2, 165.6, 139.0,
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150.5, 155.8, 155.8, 168.7. (Z)-6: HꢀNMR (500 MHz, CDCl3): δ 1.60 (s, 3H), 1.36 (s, 3H), 1.68 (s,
3H), 1.74 (s, 3H), 1.94ꢀ2.13 (m, 4H), 2.18 (m, 2H), 2.29 (m, 2H), 2.90 (t, J = 7.3, 2H), 3.45 (s, 3H),
3.46 (s, 3H), 3.53 (d, J = 7.0 , 2H), 3.80 (t, J = 7.7, 2H), 4.20 (s, 2H), 4.96ꢀ5.10 (m, 2H), 5.12 (s, 2H),
5.20 (s, 2H), 5.31ꢀ5.25 (m, 1H), 6.46 (bs, 1H), 6.93 (d, J = 8.6, 2H), 7.12 (d, J = 8.6, 2H), 7.14 (s, 1H);
13CꢀNMR (125 MHz, CDCl3): δ 16.0, 17.6, 22.8, 23.5, 25.7, 26.2, 26.6, 32.0, 33.9, 39.7, 44.4, 48.1,
55.9, 56.1, 94.5, 94.9, 101.2, 116.4, 119.8, 121.7, 121.9, 123.5, 124.2, 129.6, 131.3, 132.0, 132.2,
135.9, 139.1, 150.4, 155.8, 155.8, 168.7; HRMS (ESI) [M+Na]+: calcd for C35H47NO6Na: 600.3301;
found: 600. 3303.
Compounds 7, 8 and 9. To a solution of 6 (577 mg, 0.87 mmol, 1.0 eq.) in dry dichloromethane
was added VO(acac)2 (4 mg, 0.013 mmol, 1.5 mol%). After 5 minutes, TBHP (5.5 M in decane, 200
ꢁL, 1.1 mmol, 1.3 eq.) and TFA (13 ꢁL, 0.17 mmol, 0.2 eq.) were added and the mixture was stirred at
40 °C for 4 h. Then, the solvent was removed under reduced pressure and the residue was purified by
column chromatography on silica gel using CH2Cl2/EtOAc 4/1 as eluent affording 7 as a major
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product (279 mg, 54%), 8 (80 mg, 15%) and 9 (40 mg, mixture of diastereoisomers, 8%). 7: 1HꢀNMR
(500 MHz, CDCl3): δ 1.34 (s, 3H25), 1.57 (s, 3H24), 1.58 (s, 3H23), 1.59ꢀ1.65 (m, 2H14), 1.67 (s, 3H22),
1.96 (m, 2H18), 2.04 (m, 2H19), 2.12 (m, 2H15), 2.79 (dd, J = 5.7 and 17.8, 1H7), 2.91 (t, J = 7.5, 2H2’),
3.00 (dd, J = 5.1 and 17.8, 1H7), 3.46 (s, 3HꢀMOM), 3.47 (s, 3HꢀMOM), 3.75ꢀ3.85 (m, 2H1’), 3.93 (m,
1H8), 4.17 (m, 2H13), 5.05ꢀ5.11 (m, 2H16,20), 5.14 (s, 2HꢀMOM), 5.22 (s, 2HꢀMOM), 6.96 (d, J = 8.5,
2H5’), 7.09 (s, 1H4), 7.16 (d, J = 8.5, 2H4’); 13CꢀNMR (125 MHz, CDCl3): δ 15.9 (C24), 17.6 (C23),
19.1 (C25), 21.6 (C15), 25.6 (C22), 26.6 (C19), 26.9 (C7), 34.0 (C2’), 37.0 (C14), 39.6 (C18), 44.3 (C1’),
47.9 (C13), 55.9 (CH3ꢀMOM), 56.3 (CH3ꢀMOM), 67.6 (C8), 79.0 (C9), 94.6 (CH2ꢀMOM), 94.7 (CH2ꢀ
MOM), 100.0 (C4), 112.3 (C6), 116.5 (C5’ and C7’), 122.5 (C12), 123.6 (C16), 124.2 (C20), 129.7 (C4’
and C8’), 131.5 (C3’), 132.0 (C3), 132.7 (C21), 135.8 (C17), 148.2 (C11), 155.9 (C6’), 156.2 (C5), 168.6
(C2); HRMS (ESI) [M+Na]+: calcd for C35H47NO7Na: 616.3250; found: 616.3253; HPLC (Daicel
Chiralpak IA, iꢀPrOH/nꢀheptan 4/1, 1 mL/min, 254 nm): t8R,9S = 8.52 min (49.9%), t8S,9R = 13.92 min
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(50.1%). 8: HꢀNMR (500 MHz, CDCl3): δ 1.29 (s, 3H25), 1.59 (s, 6H24,23), 1.67 (s, 3H22), 1.71ꢀ1.81
(m, 2H14), 1.96ꢀ1.99 (m, 2H18), 2.04ꢀ2.11 (m, 2H19), 2.12ꢀ2.16 (m, 2H15), 2.83 (dd, J = 4.8 and 18.0,
1H7), 2.91 (t, J = 7.5, 2H2’), 2.96 (dd, J = 4.9 and 18.0, 1H7), 3.46 (s, 3HꢀMOM), 3.47 (s, 3HꢀMOM),
3.79 (t, J = 7.4, 2H1’), 3.93 (t, J = 4.7, 1H8), 4.16 (s, 2H13), 5.07ꢀ5.10 (m, 1H20), 5.14 (s, 2HꢀMOM),
5.14ꢀ5.17 (m, 1H16), 5.22 (s, 2HꢀMOM), 6.96 (d, J = 8.4, 2H5’), 7.08 (s, 1H4), 7.16 (d, J = 8.4, 2H4’);
13CꢀNMR (125 MHz, CDCl3): δ 15.9 (C24), 17.7 (C23), 21.4 (C25), 21.8 (C15), 25.7 (C22), 26.7 (C19),
26.9 (C7), 34.0 (C2’), 34.5 (C14), 39.7 (C18), 44.2 (C1’), 47.8 (C13), 55.9 (CH3ꢀMOM), 56.3 (CH3ꢀ
MOM), 68.1 (C8), 78.9 (C9), 94.5 (CH2ꢀMOM), 94.6 (CH2ꢀMOM), 100.0 (C4), 112.4 (C6), 116.4 (C5’
and C7’), 122.4 (C12), 123.8 (C16), 124.2 (C20), 129.7 (C4’ and C8’), 131.4 (C3’), 132.1 (C3), 132.7 (C21),
135.6 (C17), 148.0 (C11), 155.9 (C6’), 156.2 (C5), 168.5 (C2); HRMS (ESI) [M+Na]+: calcd for
C35H47NO7Na: 616.3250; found: 616.3253; HPLC (Daicel Chiralpak IC, iꢀPrOH/nꢀheptan 3/1, 1
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mL/min, 254 nm): t8S,9S = 23.25 min (51.3%), t8R,9R = 31.72 min (48.7%). 9: HꢀNMR (300 MHz,
CDCl3): δ 1.19 (s, 3H), 1.32 (s, 3H), 1.59 (s, 3H), 1.61 (s, 3H), 1.62 (s, 3H), 1.64 (s, 3H), 1.67 (s, 3H),
1.68 (s, 3H), 1.95ꢀ2.20 (m, 2x6H), 2.91 (t, J = 2.91, 2x2H), 3.19 (m, 2x2H), 3.47 (s, 2x6H), 3.80 (m,
2x2H), 4.14 (s, 2x2H), 4.78 (q, J = 4.8, 2x1H), 5.08ꢀ5.16 (m, 2x2H), 5.14 (s, 2x1H), 5.22 (s, 2x1H),
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6.96 (d, J = 7.0, 2x2H), 7.10 (s, 2x1H), 7.15 (d, J = 7.2, 2x2H); HꢀNMR (75 MHz, CDCl3): δ 16.0,
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17.7, 21.1, 21.9, 22.1, 22.9, 25.6, 26.6, 26.6, 28.1, 28.4, 33.9, 36.9, 38.8, 39.6, 44.3, 47.6, 55.9, 56.2,
73.5, 73.6, 90.3, 90.8, 101.6, 115.4, 116.5, 119.0, 119.1, 123.8, 123.9, 124.1, 124.2, 129.6, 131.5,
131.5, 132.1, 132.1, 135.0, 135.7, 135.8, 154, 1, 154.5, 155.9, 168.2; HRMS (ESI) [M+Na]+: calcd for
C35H47NO7Na: 616.3250; found: 616.3254.
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Compounds 14 and 15. To a solution of 7 (93 mg, 0.16 mmol, 1.0 eq) in dry dichloromethane (5
mL) were added (S)ꢀmethoxyphenylacetic acid (29 mg, 0.17 mmol, 1.1 eq.), dicyclohexylcarbodiimide
(42 mg, 0.20 mmol, 1.3 eq.) and 4ꢀ(dimethylamino)pyridine (2 mg, 0.016 mmol, 0.1 eq) and the
solution was stirred at room temperature for 20 h. Then, the reaction mixture was filtered and the
filtrate was concentrated under reduce pressure. The residue was purified on preparative TLC using
Et2O/PE 7/3 as eluent affording 14 (50 mg, 43%) and 15 (50 mg, 43%) as colorless oils. 14: 1HꢀNMR
(300 MHz, CDCl3): δ 0.97 (s, 3H), 1.24ꢀ1.34 (m, 2H), 1.48 (s, 3H), 1.58 (s, 3H), 1.66 (s, 3H), 1.64ꢀ
2.05 (m, 6H), 2.77 (dd, J = 6.0 and 18.0, 1H), 2.92 (t, J = 7.2, 2H), 3.09 (dd, J = 5.4 and 18.1, 1H),
3.40 (s, 3H), 3.46 (s, 6H), 3.80 (t, J = 8.0, 2H), 4.15 (d, J = 3.1, 2H), 4.76 (s, 1H), 4.89 (t, J = 6.9, 1H),
4.76ꢀ5.12 (m, 2H), 5.14 (s, 2H), 5.22 (s, 2H), 6.97 (d, J = 8.6, 2H), 7.10 (s, 1H), 7.17 (d, J = 8.6), 7.32ꢀ
7.36 (m, 3H), 7.38ꢀ7.42 (m, 2H); 13CꢀNMR (75 MHz, CDCl3): δ 15.8, 17.6, 19.2, 21.2, 24.1, 25.7,
26.6, 34.0, 36.7, 39.6, 44.3, 47.8, 55.9, 56.3, 57.2, 69.8, 82.3, 94.5, 94.6, 99.9, 111.5, 116.4, 122.3,
123.1, 124.1, 127.3, 128.6, 128.9, 129.6, 131.4, 132.0, 132.9, 135.6, 136.0, 148.0, 155.9, 155.9, 168.4,
169.9; [α]D = +29.9 (c 1.075, CHCl3) ꢀ [α]D = +24.4 (c 1.0, MeOH). 15: 1HꢀNMR (500 MHz, CDCl3):
δ 1.31 (s, 3H), 1.47ꢀ1.57 (m, 2H), 1.51 (s, 3H), 1.60 (s, 3H), 1.66 (s, 3H), 1.91ꢀ1.95 (m, 2H), 1.99ꢀ2.10
(m, 4H), 2.49 (dd, J = 5.1 and 18.1, 1H), 2.88 (dd, J = 5.2 and 18.2, 1H), 2.94 (t, J = 7.6, 2H), 3.36 (s,
3H), 3.40 (s, 3H), 3.46 (s, 3H), 3.80ꢀ3.83 (m, 2H), 4.17 (d, J = 3.1, 2H), 4.78 (s, 1H), 5.00 (t, J = 6.3,
1H), 5.05 (t, J = 6.8, 1H), 5.09 (dd, J = 6.5 and 8.2, 2H), 5.14 (s, 2H), 6.97 (d, J = 8.5, 2H), 7.04 (s,
1H), 7.18 (d, J = 8.3, 2H), 7.19 (d, J = 7.2, 2H), 7.22 (d, J = 7.0, 1H), 7.26ꢀ7.29 (m, 2H); 13CꢀNMR
(125 MHz, CDCl3): δ 15.9, 17.7, 20.1, 21.5, 23.5, 25.7, 26.6, 30.3, 32.2, 34.0, 36.8, 39.6, 44.3, 47.8,
55.9, 56.2, 57.3, 70.0, 82.3, 94.5, 94.6, 99.9, 111.2, 116.4, 122.1, 123.0, 124.1, 126.6, 128.4, 128.5,
129.7, 131.5, 132.1, 132.8, 135.7, 136.0, 147.9, 155.9, 168.5, 170.1; [α]D = +8.2 (c 1.0, CHCl3).
HRMS (ESI) [M+Na]+: calcd for C44H55NO9Na: 764.3769; found: 764.3770.
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Compound 18. To a solution of 14 (85 mg, 0.114 mmol, 1.0 eq.) in MeOH was added a solution of
MeONa in MeOH (25% w/w, 40 ꢁL, 0.17 mmol, 1.5 eq.) at 0 °C and the mixture was stirred at room
temperature for 2h. The reaction mixture was quenched with HCl 2 N and the product was extracted
with EtOAc. The combined organic layers were washed with brine, dried over MgSO4, filtered and the
filtrate concentrated under reduced pressure. Then, the crude material was purified on preparative TLC
using Et2O/PE 4/1 affording 18 (60 mg, 88%) as a colorless oil. [α]D = ꢀ11.2 (c 1.0, MeOH); HPLC
(Daicel Chiralpak IA, iꢀPrOH/nꢀheptan 4/1, 1 mL/min, 254 nm): t8R,9S = 8.63 min (2%), t8S,9R = 14.03
min (98%).
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Stachybotrin C 22. To a solution of 18 (60 mg, 0.10 mmol, 1.0 eq.) in dry MeOH (3 mL) was
added acetyl chloride (36 ꢂL, 0.50 mmol, 5.0 eq.) at 0 °C. The solution was stirred at room
temperature for 20 h. Water was added and the product was extracted with EtOAc. The combined
organic layers were washed with brine, dried over MgSO4, filtered and the filtrate concentrated under
reduced pressure. The residue was purified on preparative TLC using Et2O as eluent affording
stachybotrin C 22 as a white solid (35 mg, 69%). Mp = 90ꢀ92 °C. 1HꢀNMR (500 MHz, MeOD): δ 1.26
(s, 3H25), 1.56 (s, 6H24,23), 1.66 (s, 3H22), 1.66ꢀ1.68 (m, 2H14), 1.95ꢀ1.98 (m, 2H18), 2.01ꢀ2.07 (m,
2H19), 2.13ꢀ2.18 (m, 2H15), 2.64 (dd, J = 6.9 and 17.6, 1H7), 2.86 (t, J = 7.2, 2H2’), 2.97 (dd, J = 5.4
and 17.6, 1H7), 3.75 (t, J = 7.2, 2H1’), 3.86 (t, J = 6.1, 1H8), 4.14 (s, 2H13), 5.06 (t, J = 6.8, 1H16), 5.14
(t, J = 7.0, 1H20), 6.68 (d, J = 8.3, 2H5’,7’), 6.72 (s, 1H4), 7.04 (d, J = 8.3, 2H4’,8’); 13CꢀNMR (125 MHz,
MeOD): δ 16.0 (C24), 17.8 (C23), 18.8 (C25), 22.6 (C15), 25.9 (C22), 27.7 (C19 and C7), 34.8 (C2’), 38.5
(C14), 40.8 (C18), 45.6 (C13 and C1’), 68.4 (C8), 80.2 (C9), 100.8 (C4), 113.2 (C6), 116.3 (C5’), 116.4
(C7’), 121.6 (C12), 125.4 (C16), 125.5 (C20), 130.7 (C4’ and C5’), 130.8 (C3’), 132.2 (C3), 132.8 (C21),
136.2 (C17), 149.9 (C11), 157.1 (C6’), 157.9 (C5), 171.1 (C2); HRMS (ESI) [M+Na]+: calcd for
C31H39NO5Na: 528.2726; found: 528.2721. [α]D = ꢀ13.0 (c 1.06, MeOH) ꢀ [α]D = ꢀ14.8 (c 0.23,
MeOH).
Compound 19. Prepared from 15 following the procedure described for 18. [α]D = +12.0 (c 1.1,
MeOH); HPLC (Daicel Chiralpak IA, iꢀPrOH/nꢀheptan 4/1, 1 mL/min, 254 nm): t8R,9S = 8.48 min
(96%), t8S,9R = 13.94 min (4%).
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ent-Stachybotrin C 23. Prepared from 19 following the procedure described for 22. Identical
spectroscopic data to 22. [α]D = +13.6 (c 1.5, MeOH).
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Compounds 16 and 17. Prepared from 8 following the procedure described for 14 and 15. 16: 1Hꢀ
NMR (300 MHz, CDCl3): δ 1.06 (s, 3H), 1.19ꢀ1.43 (m, 2H), 1.48 (s, 3H), 1.62 (s, 3H), 1.70 (s, 3H),
1.77ꢀ1.83 (m, 2H), 1.89ꢀ1.94 (m, 2H, 2.00ꢀ20.5 (m, 2H), 2.86 (dd, J = 5.0 and 18.4, 1H), 2.93 (t, J =
7.6, 2H), 3.00 (dd, J = 5.2 and 18.4, 1H), 3.37 (s, 3H), 3.46 (s, 3H), 3.46 (s, 3H), 3.80 (dd, J = 6.1 and
8.4, 2H), 4.16 (d, J = 2.6, 2H), 4.74 (s, 1H), 4.74 (t, J = 7.3, 1H), 5.07ꢀ5.11 (m, 2H), 5.14 (s, 2H), 5.22
(s, 2H), 6.97 (d, J = 8.6, 2H), 7.11 (s, 1H), 7.18 (d, J = 8.6), 7.31ꢀ7.35 (m, 3H), 7.37ꢀ7.41 (m, 2H);
13CꢀNMR (75 MHz, CDCl3): δ 15.9, 17.7, 21.2, 21.4, 24.1, 25.7, 26.7, 34.0, 34.4, 39.6, 44.2, 47.8,
56.0, 56.3, 57.1, 70.3, 82.2, 94.5, 94.7, 99.9, 111.6, 116.4, 122.4, 123.0, 124.2, 127.3, 128.7, 128.9,
129.7, 131.5, 132.1, 135.4, 136.0, 148.0, 155.9, 156.0, 168.5, 170.0; [α]D = +45.4 (c 1.14, MeOH). 17:
1HꢀNMR (500 MHz, CDCl3): δ 1.23 (s, 3H), 1.58 (s, 3H), 1.61 (s, 3H), 1.61ꢀ1.70 (m, 2H), 1.69 (s,
3H), 1.92ꢀ2.09 (m, 6H), 2.55 (dd, J = 4.5 and 18.4, 1H), 2.82 (dd, J = 4.7 and 18.4, 1H), 2.94 (t, J =
7.6, 2H), 3.35 (s, 3H), 3.38 (s, 3H), 3.46 (s, 3H), 3.82 (t, J = 7.0, 2H), 4.18 (s, 2H), 4.76 (s, 1H), 5.05ꢀ
5.16 (m, 5H), 5.14 (s, 2H), 6.97 (d, J = 8.6, 2H), 7.03 (s, 1H), 7.11ꢀ7.40 (m, 7H), 7.19 (d, J = 7.2, 2H),
7.22 (d, J = 7.0, 1H), 7.26ꢀ7.29 (m, 2H); 13CꢀNMR (125 MHz, CDCl3): δ 15.9, 17.7, 21.3, 21.6, 23.4,
25.7, 26.6, 34.0, 35.2, 39.7, 44.2, 47.8, 55.9, 56.2, 57.3, 70.2, 82.2, 94.5, 94.5, 99.8, 111.3, 116.4,
122.1, 123.4, 124.2, 126.5, 128.3, 128.5, 129.7, 131.5, 132.1, 132.8, 135.6, 135.8, 147.8, 155.9, 155.9,
168.5, 170.0; [α]D = ꢀ8.7 (c 1.12, MeOH). HRMS (ESI) [M+Na]+: calcd for C44H55NO9Na: 764.3769;
found: 764.3770.
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Compound 20. Prepared from 16 following the procedure described for 18. [α]D = +22.9 (c 1.2,
MeOH); HPLC (Daicel Chiralpak IC, iꢀPrOH/nꢀheptan 3/1, 1 mL/min, 254 nm): t8S,9S = 23.55 min
(97%), t8R,9R = 32.13 min (2%).
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NMR (300 MHz, MeOD): δ 1.31 (s, 3H25), 1.53 (s, 3H24), 1.56 (s, 3H23), 1.64 (s, 3H22), 1.63ꢀ1.76 (m,
2H14), 1.93ꢀ2.22 (m, 6H18,19,15), 2.68 (dd, J = 6.6 and 17.8, 1H7), 2.86 (t, J = 7.2, 2H2’), 2.96 (dd, J =
5.5 and 17.8, 1H7), 3.76 (dt, J = 3.2 and 7.2, 2H1’), 3.86 (t, J = 5.9, 1H8), 4.16 (d, J = 1.3, 2H13), 5.06
(m, 1H16), 5.14 (dd, J = 5.7 and 7.4, 1H20), 6.69 (d, J = 8.5, 2H5’,7’), 6.72 (s, 1H4), 7.04 (d, J = 8.5,
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2H4’,8’); 13CꢀNMR (75 MHz, MeOD): δ 15.9 (C24), 17.7 (C23), 22.2 (C25), 22.7 (C15), 25.9 (C22), 27.7
(C19), 27.7 (C7), 34.2 (C2’), 34.8 (C14), 40.8 (C18), 45.6 (C13 and C1’), 69.6 (C8), 80.1 (C9), 100.9 (C4),
113.5 (C6), 116.3 (C5’ and C7’), 121.6 (C12), 125.4 (C16), 125.5 (C20), 130.7 (C4’ and C8’), 130.8 (C3’),
132.2 (C3), 132.8 (C21), 136.2 (C17), 149.8 (C11), 157.1 (C6’), 158.0 (C5), 171.1 (C2); HRMS (ESI)
[M+Na]+: calcd for C31H39NO5Na: 528.2726; found: 528.2721. [α]D = +27.2 (c 0.47, MeOH).
Compound 21. Prepared from 17 following the procedure described for 18. [α]D = ꢀ22.4 (c 1.33,
MeOH); HPLC (Daicel Chiralpak IC, iꢀPrOH/nꢀheptan 3/1, 1 mL/min, 254 nm): t8S,9S = 23.87 min
(1%), t8R,9R = 32.66 min (99%).
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Compound 25. Prepared from 21 following the procedure described for 22. Identical spectroscopic
data to 24. [α]D = ꢀ23.7 (c 0.35, MeOH).
(E)-2-(3,7-Dimethylocta-2,6-dienyl)phenol (E)-10.9 To a solution of phenol (100 mg, 1.06 mmol,
1.0 eq.) in dry Et2O (3 mL) was added sodium (73 mg, 3.18 mmol, 3.0 eq.) and the mixture was stirred
at room temperature for 1 h. Then, (E)ꢀ1ꢀbromoꢀ3,7ꢀdimethylꢀoctaꢀ2,6ꢀdiene (230 mg, 1.06 mmol, 1.0
eq.) diluted in dry Et2O (2 mL) was added and the solution was heated at 30 °C overnight. Sodium was
then removed by filtration, HCl 0.1 N was added and the product was extracted with Et2O. The
combined organic layers were washed with brine, dried over MgSO4, filtered and the filtrate
concentrated under reduced pressure. The residue was purified by column chromatography on silica
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gel using EP/Et2O 4/1 as eluent affording (E)-10 as a light brown oil (170 mg, 70%). HꢀNMR (300
MHz, CDCl3): δ 1.60 (s, 3H), 1.69 (s, 3H), 1.77 (s, 3H), 2.11 (m, 4H), 3.37 (d, J = 7.2, 2H), 4.98ꢀ5.18
(m, 1H), 5.26ꢀ5.43 (m, 1H), 6.81 (dd, J = 1.3 and 8.4, 1H), 6.86 (td, J = 1.2 and 7.5, 1H), 7.10 (d, J =
7.7, 1H), 7.13 (m, 1H); 13CꢀNMR (75 MHz, CDCl3): δ 16.1, 17.7, 25.7, 26.4, 29.7, 39.7, 115.7, 120.7,
121.6, 123.8, 126.8, 127.5, 129.9, 131.9, 138.4, 154.4; HRMS (ESI) [M+H]+: calcd for C16H23O:
231.17489; found: 231.1749.
(2R*,3S*)-2-Methyl-2-(4-methylpent-3-enyl)chroman-3-ol trans-11.7 Prepared from (E)-10
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following the procedure described for 7 and 8. HꢀNMR (500 MHz, CDCl3): δ 1.33 (s, 3H), 1.55 (s,
3H), 1.54ꢀ1.69 (m, 2H), 1.66 (s, 3H), 2.07ꢀ2.19 (m, 2H), 2.78 (dd, J = 5.7 and 16.8, 1H), 3.05 (dd, J =
4.9 and 16.8, 1H), 3.87 (t, J = 5.3, 1H), 5.08 (tt, J = 1.2 and 7.1 , 1H), 6.82 (d, J = 8.2, 1H), 6.86 (t, J =
7.4, 1H), 7.05 (d, J = 7.4, 1H), 7.11 (t, J = 7.8, 1H); 13CꢀNMR (125 MHz, CDCl3): δ 17.6, 19.3, 21.7,
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25.6, 31.1, 37.1, 68.2, 78.6, 117.3, 119.0, 120.5, 123.9, 127.6, 130.0, 132.0, 152.8; HRMS (ESI)
[M+Na]+: calcd for C16H22O2Na: 269.15175; found: 269.1516.
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(Z)-2-(3,7-Dimethylocta-2,6-dienyl)phenol (Z)-10.10 Prepared from phenol and (Z)ꢀ1ꢀbromoꢀ3,7ꢀ
dimethylꢀoctaꢀ2,6ꢀdiene13 following the procedure described for (E)-10. 1HꢀNMR (300 MHz, CDCl3):
δ 1.63 (s, 3H), 1.70 (s, 3H), 1.77 (s, 3H), 2.06ꢀ2.28 (m, 4H), 3.37 (d, J = 7.1, 1H), 5.09ꢀ5.20 (m, 1H),
5.32 (t, J = 7.2, 1H), 6.80 (dd, J = 1.2 and 8.4, 1H), 6.86 (td, J = 1.2 and 7.6, 1H), 7.10 (d, J = 7.5,
1H), 7.13 (m, 1H); 13CꢀNMR (75 MHz, CDCl3): δ 17.6, 23.4, 25.7, 26.3, 29.4, 32.0, 115.6, 120.7,
122.4, 123.8, 126.9, 127.5, 129.9, 132.2, 138.5, 154.2; HRMS (ESI) [M+H]+: calcd for C16H23O:
231.17489; found: 231.1749.
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(2R*,3R*)-2-Methyl-2-(4-methylpent-3-enyl)chroman-3-ol cis-11. Prepared from (Z)-10
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following the procedure described for 7 and 8. HꢀNMR (300 MHz, CDCl3): δ 1.27 (s, 3H), 1.58 (s,
3H), 1.66 (s, 3H), 1.66ꢀ1.82 (m, 2H), 2.09ꢀ2.17 (m, 2H), 2.78 (dd, J = 4.8 and 17.0, 1H), 3.05 (dd, J =
4.8 and 17.0, 1H), 3.86 (t, J = 4.8, 1H), 5.14 (tt, J = 1.4 and 7.1, 1H), 6.83 (d, J = 8.1, 1H), 6.88 (dd, J
= 1.1 and 7.4, 1H), 7.06 (d, J = 7.5, 1H), 7.11 (dt, J = 1.5 and 7.4, 1H). 13CꢀNMR (75 MHz, CDCl3): δ
17.6, 21.3, 21.8, 25.6, 31.0, 34.7, 68.5, 78.4, 117.3, 119.0, 120.5, 124.1, 127.6, 130.1, 131.8, 152.6;
HRMS (ESI) [M+Na]+: calcd for C16H22O2Na: 269.15175; found: 269.1516.
(2R*,3S*)-2-Methyl-2-(4-methylpent-3-enyl)chroman-3-yl 4-iodobenzoate 12. To a solution of
trans-11 (92 mg, 0.37 mmol, 1.0 eq) in dry dichloromethane (2 mL) were added pꢀiodobenzoic acid
(102 mg, 0.41 mmol, 1.1 eq.), DCC (99 mg, 0.48 mmol, 1.3 eq.) and DMAP (5 mg, 0.04 mmol, 0.1
eq) and the solution was stirred at room temperature for 20 h. Then, the reaction mixture was filtered
to remove DCU and the filtrate was concentrated under reduce pressure. The residue was purified on
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preparative TLC using EP/Et2O 9/1 as eluent affording 12 as a pale yellow solid (120 mg, 68%). Hꢀ
NMR (300 MHz, CDCl3): δ 1.38 (s, 3H), 1.55 (s, 3H), 1.68 (s, 3H), 1.67ꢀ1.75 (m, 2H), 2.16 (m, 2H),
2.91 (dd, J = 5.6 and 17.2, 1H), 3.25 (dd, J = 5.1 and 17.2, 1H), 5.05 (t, J = 6.9, 1H), 5.32 (t, J = 5.4,
2H), 6.88 (m, 2H), 7.04 (d, J = 7.0, 1H), 7.14 (t, J = 7.0, 1H), 7.70 (d, J = 8.5, 2H), 7.80 (d, J = 8.4,
2H). 13CꢀNMR (75 MHz, CDCl3): δ 17.5, 20.1, 21.6, 25.6, 28.2, 37.2, 70.8, 101.0, 117.2, 118.3, 120.5,
123.6, 127.7, 129.4, 129.5, 131.1, 132.1, 137.8, 152.7, 165.4; HRMS (ESI) [M+Na]+: calcd for
C23H25O3INa: 499.0746; found: 499.0744.
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Acknowledgment This research has been performed as part of the IndoꢀFrench “Joint Laboratory
for Sustainable Chemistry at Interfaces”. We thank the CNRS, France, and CSIR, India, for support.
We also thank the Ministère de la Recherche, France, for the fellowship of Maiwenn Jacolot and the
PRISM plateform for NMR analysis (Université de Rennes 1, UFR Sciences Biologiques et
Pharmaceutiques, 2 avenue du Prof Léon Bernard, Fꢀ35043 Rennes Cedex, France).
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Supporting Information Available Copies of H, 13C NMR spectra of all compounds, Xꢀray and
HPLC analysis. This material is available free of charge via the Internet at http://pubs.acs.org.
R
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