Total synthesis of the proposed structure of pestalotioprolide A

Article abstract of DOI:10.1016/j.tetasy.2015.06.020

Abstract A chiron approach to the synthesis of the proposed structure of pestalotioprolide A, a 14-membered unsaturated macrolide isolated from the mangrove-derived fungus Pestalotiopsis sp. PSU-MA119, starting from d-(+)-gluconic acid δ-lactone is descri

Full text of DOI:10.1016/j.tetasy.2015.06.020

Tetrahedron: Asymmetry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Total synthesis of the proposed structure of pestalotioprolide A
⇑
Kwanruthai Tadpetch , Laksamee Jeanmard, Vatcharin Rukachaisirikul
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
a r t i c l e i n f o
a b s t r a c t
Article history:
A chiron approach to the synthesis of the proposed structure of pestalotioprolide A, a 14-membered
unsaturated macrolide isolated from the mangrove-derived fungus Pestalotiopsis sp. PSU-MA119, starting
Received 27 May 2015
Accepted 29 June 2015
Available online xxxx
from
D-(+)-gluconic acid d-lactone is described. The key strategies to assemble the macrolactone include
Yamaguchi esterification and ring-closing metathesis.
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
The retrosynthetic approach of 1 is outlined in Scheme 1. Ring-
closing metathesis (RCM) was envisioned to be the key macrocy-
clization strategy at C8–C9 (Z)-olefin. The RCM diene precursor 3
would be united by esterification of the two key fragments: (S)-
The 14-membered macrolides are an important class of
fungal polyketide metabolites that possess diverse biological and
pharmacological profiles, in particular, antibiotic activity.1
Pestalotioprolide A 1 is a new 14-membered macrolide isolated
along with the previously reported seiricuprolide 2 from the
mangrove-derived fungus Pestalotiopsis sp. PSU-MA119 by
hept-6-en-2-ol 4 and a,b-unsaturated acid 5. The a,b-unsaturated
acid moiety in 5 would then be constructed via a Wittig olefination
of aldehyde 6. The chiral allylic alcohol moiety of 6 would be acces-
sible from chiral epoxide 7. All stereogenic centers of 7 could be
Rukachaisirikul et al. (Fig. 1).2 Structurally, 1 is an (E)-
a,b-
directly mapped onto D-(+)-gluconic acid d-lactone 8, a readily
unsaturated macrolactone containing four contiguous hydroxyl
groups and a (Z)-double bond, hence a dihydroxy analog of 2.
Based on the 1H NMR coupling constants and the observed specific
rotations of its acetate derivatives, the relative and absolute config-
urations of 1 were assigned to be identical to those of the (5R,6R)-
bromohydrin derivative of 2. In order to prove the stereochemistry
of the natural product and due to the potential biological activities
of this group of macrolides, we set out a synthetic program for such
compounds. Herein we report the total synthesis of the proposed
structure of pestalotioprolide A by a chiron approach.
available chiral building block.
2. Results and discussion
The synthesis began with the preparation of chiral epoxide 7
from D-(+)-gluconic acid d-lactone 8 via four high-yielding steps fol-
lowing the procedures reported by Murphy3 and Ma.4 Epoxide 7 was
further elaborated into diol 11 via a 3-step sequence reported by
Meshram.5 Regioselective opening of 7 with sulfonium ylide (gener-
ated in situ by treatment of trimethylsulfonium iodide with n-BuLi)
gave enantioenriched homoallylic alcohol 9 in excellent yield,
which after protection with tert-butyldiphenylsilyl (TBDPS) group
gave silyl ether 10 in 70% yield along with unreacted starting mate-
rial. Selective deprotection of the terminal acetonide using
CuCl2ꢀ2H2O in MeCN at 0 °C furnished the desired diol 11 in 61%
yield (based on recovered starting bisacetonide). To achieve the req-
uisite aldehyde 6, diol 11 required selective oxidation of the primary
alcohol moiety in the presence of a secondary alcohol. This was
accomplished by selective protection of the primary alcohol with
benzoyl chloride to give benzoate ester 12 in 73% yield, followed
by conversion of the secondary alcohol into the corresponding
t-butyldimethylsilyl (TBS) ether 13. Subsequent removal of the
benzoate employing DIBALH in CH2Cl2 at ꢁ78 °C yielded the
desired primary alcohol 14 in 77% yield. Oxidation of 14 using
(diacetoxy)iodobenzene (PhI(OAc)2) in the presence of catalytic
OH
O
OH
OH
OH
OH
OH
O
O
CH3
O
CH3
O
pestalotioprolide A 1
2
seiricuprolide
Figure 1. Structures of pestalotioprolide A 1 and seiricuprolide 2.
⇑
Corresponding author. Tel.: +66 74 288437; fax: +66 74 558841.
E-mail address: kwanruthai.t@psu.ac.th (K. Tadpetch).
http://dx.doi.org/10.1016/j.tetasy.2015.06.020
0957-4166/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Tadpetch, K.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.06.020

2
K. Tadpetch et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
TEMPO in CH2Cl2 at room temperature gave aldehyde 6 in 95%
yield. Further treatment of with stabilized phosphonium
ylide Ph3P@CHCO2Et in CH2Cl2 at room temperature furnished
(E)- ,b-unsaturated ester 15 in 90% yield. Finally, basic hydrolysis
of the resultant ester using aqueous LiOH in THF/MeOH afforded
the requisite ,b-unsaturated acid 5 in 91% yield (see Scheme 2).
With the key acid 5 in hand, we proceeded to complete the
synthesis of RCM diene precursor 3. Coupling of carboxylic acid 5
and (S)-hept-6-en-2-ol 46 was achieved under Yamaguchi
conditions7 to afford diene 16 in 87% yield. The stage was then
set for the crucial ring-closing metathesis. RCM reactions to
assemble large rings (P10 atoms) are challenging and not always
predictable due to decreased ring strain and the probability of
end-to-end encounters8 and the limited number of examples on
the synthesis of 14-membered non-aromatic macrolides by RCM
are precedented.9 Direct ring-closing metathesis of 16 using a
second generation Grubbs (Grubbs II) catalyst was unsuccessful
most likely due to the steric congestion of the TBDPS group.10
Hence, both silyl protecting groups of 16 were removed with
TBAF to give diol 3. Exposure of 3 to the second generation
Grubbs catalyst (10 mol %) in refluxing CH2Cl2 at a concentration
of 3 mM led to the undesired (E)-isomer as the major product
in a very low yield along with trace amounts of the (Z)-isomer
and several other unidentified products. Lowering the reaction
temperature or decreasing the reaction concentration did not
improve the reaction outcome. Replacing the Grubbs II catalyst
with the less reactive first generation Grubbs (Grubbs I) catalyst
(20 mol %) in refluxing CH2Cl2 provided the macrocycle with the
6
a
a
ring closing
metathesis
OH
O
O
O
OH
7
O
9
5
OH
OR
OH
11
OH
3
+
OTBS
OH
OH
CH3
13
O
1
HO
O
Wittig
olefination
esterification
CH3
O
O
CH3
O
4
1
5
R = TBDPS
3
O
O
O
O
O
HO
HO
O
O
O
OH
O
OR
OTBS
OH
O
6
7
D-(+)-gluconic acid δ-lactone 8
R = TBDPS
Scheme 1. Retrosynthesis of pestalotioprolide A 1.
O
O
O
O
O
TBDPSCl
imidazole
HO
HO
O
refs. 3 and 4
Me3SI, n-BuLi
O
O
THF, −30oC
OH
DMF, 60oC
70%
OH
O
97%
O
O
OH
O
9
8
7
O
O
O
O
O
O
TBSCl, imidazole
cat DMAP
BzCl, Et3N
CuCl2.2H2O
CH2Cl2, 0oC to rt
73%
TBDPSO
TBDPSO
10
TBDPSO
DMF, 60oC
94%
MeCN, 0oC
61%
OH
OH
O
O
OH
OBz
12
11
O
O
O
O
PhI(OAc)2
O
DIBALH
cat TEMPO
TBDPSO
CH2Cl2, −78oC
TBDPSO
CH2Cl2, rt
95%
TBDPSO
OTBS
OTBS
OTBS
77%
6
O
14
OH
13
OBz
O
O
O
O
CO2Et
LiOH
Ph3P
TBDPSO
EtO
TBDPSO
HO
THF:MeOH:H2O, rt
91%
OTBS
15
OTBS
CH2Cl2, rt
90%
5
O
O
Scheme 2. Synthesis of a,b-unsaturated acid 5.
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K. Tadpetch et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
3
O
O
O
O
2,4,6-trichlorobenzoyl chloride
OR
O
+
TBDPSO
HO
Et3N, DMAP, toluene, rt
87%
OTBS
OH
CH3
OTBS
O
16
R = TBDPS
5
4
CH3
O
O
O
O
O
TBAF
Grubbs I (50 mol%)
2M HCl
OH
O
1
OH
O
OH
THF, 0 oC to rt
91%
CH2Cl2, 40oC
35% brsm
OH
17
THF, rt
70%
O
CH3
O
3
CH3
Scheme 3. Completion of the synthesis of 1.
Table 1
was reported at d 68.2 ppm. This observation could result from
the dissimilarity in the absolute configuration of the stereogenic
center at C-5 of the synthetic sample and the natural product.
Enhancement of signal intensity of H-5 upon irradiation of H-4 in
the NOEDIFF experiment suggested that H-4 and H-5 occupied
the same side of the molecule, hence supporting the configurations
at C-4 and C-5 of synthetic 1. Moreover, the cis-relationship
between H-6 and H-7 was also confirmed by strong NOE
correlations between those protons, which further supported the
stereochemistry of synthetic 1. However, NOE data were inade-
quate to conclusively assign the relative configurations between
Comparison of 1H NMR (300 MHz) and 13C NMR (75 MHz) data of natural product and
synthetic 1
Position
Natural product
dH (mult., J in Hz)
Synthetic 1
dC
dH (mult., J in Hz)
dC
1
2
3
4
5
6
7
8
9
10
165.6
125.6
143.0
71.9
166.3
123.8
144.6
72.4
6.26 (d, 15.6)
6.86 (dd, 15.6, 7.0)
4.73 (m)
6.19 (d, 15.6)
6.86 (dd, 15.6, 3.6)
4.63 (m)
4.42 (m)
68.2
3.98 (m)
73.3
3.59 (dd, 7.2, 2.0)
4.45 (m)
5.57 (m)
73.8
68.6
129.0
133.0
29.8
3.40 (d, 7.8)
4.32 (d, 4.5)
5.57 (m)
72.2
69.3
129.8
132.1
29.7
C-5 and C-6. In addition, the specific rotation of synthetic 1 was
27
5.47 (m)
5.45 (m)
observed as ꢁ127.6 (c 0.15, CHCl3), while [
a
]
D
of the natural pro-
a: 2.20 (m)
b: 1.95 (m)
a: 1.57 (m)
b: 1.11 (m)
a: 1.84 (m)
b: 1.49 (m)
5.02 (m)
a: 2.16 (m)
b: 1.92 (m)
a: 1.57 (m)
b: 1.00 (m)
a: 1.79 (m)
b: 1.44 (m)
5.01 (m)
duct was reported to be ꢁ18.1 (c 0.15, CHCl3). Since the absolute
stereochemistry of synthetic 1 was derived from -(+)-gluconic
D
11
12
26.0
35.0
26.3
35.5
acid d-lactone and the stereochemical integrity should be retained
during the synthesis, the structure of the synthetic sample was
assigned as 1. Further studies may be warranted for the determina-
tion of the absolute stereochemistry of the natural product.
13
14
73.2
20.6
72.9
20.8
1.30 (d, 6.3)
1.29 (d, 6.3)
3. Conclusion
requisite (Z)-alkene as the major product with a much cleaner but
slower conversion. Increasing the catalyst loading to 50 mol % gave
a higher conversion but led to other side products while the
desired macrocycle 17 was obtained in a similar yield (35% based
on recovered starting diene) to that of the reaction performed with
20 mol % of the catalyst. Removal of the acetonide protecting group
with 2 M HCl in THF smoothly gave the desired target 1 in 70%
yield (see Scheme 3).
In conclusion, the total synthesis of the proposed structure of
pestalotioprolide A 1 has been accomplished in 13 steps in 3.3%
overall yield from chiral epoxide 7 derived from a chiral building
block D-(+)-gluconic acid d-lactone. The key features of the synthe-
sis include Yamaguchi esterification and ring-closing metathesis
to construct the 14-membered unsaturated macrolactone. Our
synthesis suggested that a stereochemical revision of the natural
product would be warranted.
Most of the 1H and 13C NMR data of synthetic 1 were in good
agreement with those of the natural product although minor dif-
ferences were noted (Table 1). One of the noticeable minor differ-
ences was the vicinal coupling constants between H-3 and H-4,
which appeared to be 3.6 Hz in synthetic 1 and 7.0 Hz in the natu-
ral product. Literature precedents have shown that vicinal coupling
constants between olefinic and adjacent oxymethine protons in
some 14-membered unsaturated macrolactones or synthetic inter-
mediates with similar structural and stereochemical motif can vary
significantly (from 3 to 7 Hz) depending upon the stereochemical
and conformational framework.11 The major discrepancy, however,
was the chemical shifts of oxymethine protons and carbons at the
5-position. For synthetic 1, H-5 appeared as a multiplet at d
4.03–3.93 ppm, whereas H-5 of the natural product was reported
at d 4.42 ppm as a multiplet. The 13C chemical shifts at the
5-position also significantly differed: C-5 of synthetic 1 resonated
at d 73.3 ppm, while the same carbon of the natural products
4. Experimental
4.1. General information
Unless otherwise stated, all reactions were performed under an
argon atmosphere in an oven- or flamed-dried glassware. Solvents
were used as received from suppliers or distilled prior to use using
standard procedures. All other reagents were obtained from
commercial sources and used without further purification.
Column chromatography was performed on SiliaFlashÒ G60 Silica
(60–200 lM, Silicycle). Thin-layer chromatography (TLC) was
performed on SiliaPlate™ R10011B-323 (Silicycle). 1H, 13C and 2D
NMR spectroscopic data were recorded on a 300 MHz Bruker
FTNMR Ultra Shield spectrometer. Infrared (IR) spectra were
recorded on a Perkin Elmer 783 FTS165 FT-IR spectrometer.
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4
K. Tadpetch et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
High-resolution mass spectra were obtained on a liquid chro-
matograph–mass spectrometer (2690, LCT, Waters, Micromass).
chromatography (5% EtOAc/hexanes) yielded the title compound
as a colorless oil (3.88 g, 76%): Rf = 0.37 (40% EtOAc/hexanes);
The optical rotations were recorded on
polarimeter.
a
JASCO P-1020
[a]
25 = ꢁ16.3 (c 0.1, CHCl3); 1H NMR (300 MHz, CDCl3) d 7.74–
D
7.61 (m, 4H), 7.49–7.32 (m, 6H), 5.86 (ddd, J = 17.4, 11.1, 6.0 Hz,
1H), 5.12 (app d, J = 11.1 Hz, 1H), 5.07 (app d, J = 17.4 Hz, 1H),
4.53–4.46 (m, 1H), 3.92 (app t, J = 7.8 Hz, 1H), 3.86–3.74 (m, 2H),
3.71 (app d, J = 4.8 Hz, 1H), 3.69–3.62 (m, 1H), 2.80 (br s, 2H),
1.28 (s, 6H), 1.11 (s, 9H); 13C NMR (75 MHz, CDCl3) d 136.1,
136.0, 135.0, 132.6, 132.5, 130.2, 130.1, 127.8, 127.6, 117.9,
109.0, 82.4, 77.1, 73.8, 72.5, 64.0, 27.1, 26.8, 19.3; IR (neat) 3706,
3049, 2933, 2859, 1428, 1380 cmꢁ1; HRMS (ESI) m/z calcd for
4.2. Experimental procedures
4.2.1. (S)-1-((4R,40R,5R)-2,2,20,20-Tetramethyl-4,40-bi(1,3-dioxolan)-
5-yl)prop-2-en-1-ol 9
To
a
suspension of trimethylsulfonium iodide (14.2 g,
69.6 mmol) and 74 mL of anhydrous THF at ꢁ30 °C was added
n-BuLi (45.0 mL, ca. 1.5 M solution in hexane, 67.5 mmol)
dropwise. The resultant white cloudy suspension was stirred at
C
26H36NaO5Si (M+Na)+ 479.2230, found 479.2225.
ꢁ30 °C for 50 min before
a
solution of epoxide
7
(4.47 g,
4.2.4. (R)-2-((4R,5S)-5-((S)-1-(tert-Butyldiphenylsilyloxy)allyl)-2,
2-dimethyl-1,3-dioxolan-4-yl)-2-hydroxyethyl benzoate 12
To a solution of diol 11 (5.82 g, 12.7 mmol) in CH2Cl2 (53 mL) at
0 °C was added Et3N (3.60 mL, 25.5 mmol), followed by benzoyl
chloride (2.25 mL, 19.1 mmol). The reaction mixture was stirred
under argon from 0 °C to room temperature for 13 h. The mixture
was then quenched with saturated aqueous NH4Cl (40 mL). The
aqueouslayer was extracted withCH2Cl2 (3 ꢂ 40 mL). The combined
organic layers were washed with brine, dried over anhydrous
Na2SO4, and concentrated in vacuo. The crude residue was purified
by column chromatography (hexanes–5% EtOAc/hexanes) to give
the title compound as a colorless oil (5.22 g, 73%): Rf = 0.35 (20%
18.3 mmol) in THF (15 mL) was slowly added. The white cloudy
mixture was stirred under Ar at ꢁ30 °C for 40 min before it was
quenched with saturated aqueous NH4Cl (120 mL). The organic
layer was separated and the aqueous layer was extracted with
EtOAc (3 ꢂ 80 mL). The combined organic layers were washed with
brine, dried with anhydrous Na2SO4, and concentrated in vacuo to
give a yellow oil. Purification of the crude residue by silica gel col-
umn chromatography with 10% EtOAc/hexanes as an eluent
yielded the title compound as a light yellow oil (4.62 g, 97%):
Rf = 0.26 (20% EtOAc/hexanes); [
a]
25 = ꢁ25.4 (c 0.1, CHCl3); 1H
D
NMR (300 MHz, CDCl3) d 5.99 (ddd, J = 17.1, 10.5, 4.8 Hz, 1H),
5.39 (app d, J = 17.1 Hz, 1H), 5.24 (app d, J = 10.5 Hz, 1H),
4.36–4.29 (m, 1H), 4.19–3.94 (m, 4H), 3.91–3.82 (m, 1H), 1.42 (s,
3H), 1.40 (s, 3H), 1.37 (s, 3H), 1.34 (s, 3H); 13C NMR (75 MHz,
CDCl3) d 137.4, 116.0, 110.0, 109.6, 82.5, 77.3, 76.9, 70.8, 67.8,
27.1, 27.0, 26.5, 25.2; IR (neat) 3473, 3080, 2988, 2936, 1373,
EtOAc/hexanes); [
a]
D
25 = ꢁ8.8 (c 0.1, CHCl3); 1H NMR (300 MHz,
CDCl3) d 8.10–8.02 (m, 2H), 7.74–7.63 (m, 4H), 7.55 (tt, J = 7.5,
1.2 Hz, 1H), 7.48–7.30 (m, 8H), 5.89 (ddd, J = 17.4, 10.8, 6.0 Hz,
1H), 5.09 (app d, J = 10.8 Hz, 1H), 5.04 (app d, J = 17.4 Hz, 1H), 4.61
(dd, J = 11.7, 2.7 Hz, 1H), 4.51–4.45 (m, 1H), 4.36 (dd, J = 11.7,
6.0 Hz, 1H), 4.06 (app t, J = 7.5 Hz, 1H), 3.99–3.91 (m, 2H), 1.32 (s,
6H), 1.09 (s, 9H); 13C NMR (75 MHz, CDCl3) d 166.8, 136.1, 136.0,
135.6, 133.0, 132.9, 132.87, 132.82, 130.1, 129.9, 129.7, 128.4,
127.8, 127.6, 117.8, 109.3, 82.6, 76.4, 74.2, 71.5, 66.5, 27.1, 26.9,
19.4; IR (neat) 3698, 2933, 2859, 1724, 1276, 1113 cmꢁ1; HRMS
(ESI) m/z calcd for C33H40NaO6Si (M+Na)+ 583.2492, found 583.2498.
;
1215 cmꢁ1 HRMS (ESI) m/z calcd for C13H22NaO5 (M+Na)+
281.1365, found 281.1359.
4.2.2. tert-Butyldiphenyl((S)-1-((4R,40R,5S)-2,2,20,20-tetramethyl-
4,40-bi(1,3-dioxolan)-5-yl)allyloxy)silane 10
To a solution of allylic alcohol 9 (300.8 mg, 1.16 mmol) in DMF
(2.5 mL) at room temperature was added imidazole (245.2 mg,
3.60 mmol), followed by TBDPSCl (0.45 mL, 475.6 mg, 1.73 mmol).
The reaction mixture was heated at 60 °C overnight before being
cooled to room temperature and diluted with EtOAc (5 mL). Next,
H2O (5 mL) was added and the organic layer was separated. The
aqueous layer was then extracted with EtOAc (5 ꢂ 3 mL). The com-
bined organic layers were washed with brine, dried over anhydrous
Na2SO4, and concentrated in vacuo. Purification of the crude residue
by silica gel column chromatography with 2–5–10% EtOAc/hexanes
as an eluent yielded the title compound as a colorless oil (333.9 mg,
70%) and 52.7 mg of recovered 9: Rf = 0.55 (20% EtOAc/hexanes);
4.2.5. (R)-2-(tert-Butyldimethylsilyloxy)-2-((4S,5S)-5-((S)-1-(tert-
butyldiphenylsilyloxy)allyl)-2,2-dimethyl-1,3-dioxolan-4-yl)eth-
ylbenzoate 13
To a solution of alcohol 12 (2.00 g, 3.57 mmol) in DMF (9 mL)
were added DMAP (0.13 g, 1.07 mmol) and imidazole (0.976 g,
14.3 mmol), followed by tert-butyldimethylsilyl chloride (1.62 g,
10.7 mmol). The reaction mixture was then stirred at 60 °C for
4 h, after which the mixture was cooled to room temperature
before H2O (30 mL) and EtOAc (30 mL) were added. The organic
phase was separated and the aqueous layer was extracted with
EtOAc (3 ꢂ 30 mL). The combined organic layers were washed with
H2O (50 mL) and brine (30 mL), dried over anhydrous Na2SO4, and
concentrated in vacuo. The crude residue was purified by column
chromatography (hexanes–3% EtOAc/hexanes) to yield the desired
title compound as a colorless oil (2.26 g, 94%): Rf = 0.57 (10%
[a
]
D
25 = ꢁ3.3 (c 0.1, CHCl3); 1H NMR (300 MHz, CDCl3) d 7.78–7.68
(m, 4H), 7.48–7.33 (m, 6H), 5.92 (ddd, J = 17.4, 10.2, 7.2 Hz, 1H),
5.00 (d, J = 10.2 Hz, 1H), 4.93 (d, J = 17.4 Hz, 1H), 4.37 (dd, J = 7.2,
3.9 Hz, 1H), 4.21–4.12 (m, 2H), 4.06–3.97 (m, 1H), 3.92–3.82 (m,
2H), 1.40 (s, 6H), 1.36 (s, 6H), 1.11 (s, 9H); 13C NMR (75 MHz,
CDCl3) d 136.9, 136.09, 136.08, 134.0, 133.7, 129.7, 129.6, 127.5,
127.4, 117.4, 109.7, 109.4, 82.9, 77.3, 76.9, 75.1, 66.5, 27.5, 27.3,
27.1, 26.4, 25.4, 19.5; IR (neat) 3073, 2987, 2934, 2859, 1371,
1215 cmꢁ1; HRMS (ESI) m/z calcd for C29H40NaO5Si (M+Na)+
519.2543, found 519.2540.
EtOAc/hexanes); [
a]
D
25 = ꢁ3.5 (c 0.1, CHCl3); 1H NMR (300 MHz,
CDCl3) d 8.04 (d, J = 7.2 Hz, 2H), 7.74–7.65 (m, 4H), 7.56 (t,
J = 7.2 Hz, 1H), 7.47–7.27 (m, 8H), 5.89 (ddd, J = 17.4, 10.5, 7.5 Hz,
1H), 4.92 (d, J = 10.5 Hz, 1H), 4.79 (d, J = 17.4 Hz, 1H), 4.52 (dd,
J = 11.7, 3.6 Hz, 1H), 4.38 (dd, J = 11.7, 5.1 Hz, 1H), 4.34–4.24 (m,
2H), 4.15–4.06 (m, 1H), 4.04 (dd, J = 6.9, 3.0 Hz, 1H), 1.42 (s, 3H),
1.39 (s, 3H), 1.07 (s, 9H), 0.84 (s, 9H), 0.09 (s, 3H), 0.07 (s, 3H);
13C NMR (75 MHz, CDCl3) d 166.5, 137.1, 136.1, 136.0, 134.0,
133.5, 132.9, 130.2, 129.71, 129.67, 129.5, 128.3, 127.5, 127.3,
117.1, 109.5, 82.2, 77.7, 75.6, 72.0, 66.2, 27.8, 27.2, 27.1, 25.8,
25.7, 19.5, 18.0, ꢁ4.4; IR (neat) 3073, 2932, 2858, 1726, 1273,
1113 cmꢁ1; HRMS (ESI) m/z calcd for C39H54NaO6Si2 (M+Na)+
697.3357, found 697.3359.
4.2.3. (R)-1-((4R,5S)-5-((S)-1-(tert-Butyldiphenylsilyloxy)allyl)-
2,2-dimethyl-1,3-dioxolan-4-yl)ethane-1,2-diol 11
To a solution of acetonide 10 (6.89 g, 13.9 mmol) in MeCN
(67 mL) at 0 °C was added CuCl2ꢀ2H2O (2.60 g, 15.2 mmol). The
reaction mixture was then stirred at 0 °C for 2 h before solid
NaHCO3 was added. The brown solution was filtered and
concentrated in vacuo. Purification of the crude residue by column
Please cite this article in press as: Tadpetch, K.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.06.020

K. Tadpetch et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
5
4.2.6. (R)-2-(tert-Butyldimethylsilyloxy)-2-((4S,5S)-5-((S)-1-(tert-
butyldiphenylsilyloxy)allyl)-2,2-dimethyl-1,3-dioxolan-4-yl)etha-
nol 14
(ddd, J = 17.4, 10.8, 7.5 Hz, 1H), 4.90 (d, J = 10.8 Hz, 1H), 4.74 (d,
J = 17.4 Hz, 1H), 4.41 (td, J = 5.1, 1.5 Hz, 1H), 4.29–4.19 (m, 3H),
4.13 (dd, J = 7.5, 4.8 Hz, 1H), 3.92 (dd, J = 7.5, 3.3 Hz, 1H), 1.42 (s,
3H), 1.37 (s, 3H), 1.32 (t, J = 7.2 Hz, 3H), 1.08 (s, 9H), 0.89 (s, 9H),
0.07 (s, 3H), 0.06 (s, 3H); 13C NMR (75 MHz, CDCl3) d 166.1, 147.2,
137.1, 136.1, 136.0, 134.1, 133.5, 129.7, 129.5, 127.5, 127.3, 122.3,
117.2, 109.6, 81.6, 79.4, 75.5, 73.0, 60.4, 27.5, 27.3, 27.1, 25.9, 19.5,
18.2, 14.3, ꢁ4.4, ꢁ4.6; IR (thin film) 3074, 2933, 2859, 1724,
1257 cmꢁ1; HRMS (ESI) m/z calcd for C36H54NaO6Si2 (M+Na)+
661.3357, found 661.3358.
To a solution of benzoate 13 (2.19 g, 3.24 mmol) in CH2Cl2
(28 mL) at ꢁ78 °C was slowly added DIBALH (1.0 M in cyclohexane,
10.3 mL, 10.3 mmol). The reaction mixture was then stirred under
an atmosphere of argon at the same temperature for 1 h. The mix-
ture was quenched with saturated aqueous NH4Cl (40 mL), diluted
with 20 mL of CH2Cl2, and allowed to warm to room temperature
before it was filtered through a pad of Celite. The aqueous
phase of the filtrate was extracted with CH2Cl2 (3 ꢂ 30 mL). The
combined organic phases were washed with brine, dried over
anhydrous Na2SO4, and then concentrated in vacuo. The crude
product was purified by column chromatography (2–5%
EtOAc/hexanes) to give the title compound as a colorless oil
4.2.9. (R,E)-4-(tert-Butyldimethylsilyloxy)-4-((4S,5S)-5-((S)-1-
(tert-butyldiphenylsilyloxy)allyl)-2,2-dimethyl-1,3-dioxolan-
4-yl)but-2-enoic acid 5
To a solution of a,b-unsaturatedester 15(0.120 g, 0.188 mmol) in
(1.42 g, 77%): Rf = 0.48 (20% EtOAc/hexanes); [a]
25 = +5.8 (c 0.1,
D
3 mL of THF:MeOH:H2O (8:1:1) at room temperature was added
LiOHꢀH2O (80.0 mg, 1.91 mmol) in one portion. The mixture was
stirred at ambient temperature for 4.5 h after which it was diluted
with 3 mL of H2O and neutralized with 1 M HCl. The organic layer
was separated and the aqueous layer was extracted with EtOAc
(4 ꢂ 5 mL). The combined organic layers were washed with brine,
dried over anhydrous Na2SO4, and concentrated in vacuo.
Purification of the crude residue by column chromatography
(20–40% EtOAc/hexanes) provided the title compound as a colorless
CHCl3); 1H NMR (300 MHz, CDCl3) d 7.77–7.65 (m, 4H), 7.47–7.30
(m, 6H), 5.92 (ddd, J = 17.4, 10.2, 7.8 Hz, 1H), 4.92 (d, J = 10.2 Hz,
1H), 4.78 (d, J = 17.4 Hz, 1H), 4.29 (dd, J = 7.8, 3.0 Hz, 1H), 4.21
(dd, J = 6.9, 6.6 Hz, 1H), 3.93 (dd, J = 6.9, 3.0 Hz, 1H), 3.83–3.76
(m, 1H), 3.73–3.60 (m, 2H), 1.44 (s, 3H), 1.38 (s, 3H), 1.09 (s, 9H),
0.86 (s, 9H), 0.11 (s, 3H), 0.06 (s, 3H); 13C NMR (75 MHz, CDCl3) d
137.4, 136.1, 134.1, 133.5, 129.8, 129.5, 127.5, 127.3, 116.9,
109.6, 82.8, 78.1, 75.4, 73.7, 64.6, 27.7, 27.2, 27.1, 25.9, 19.5,
18.0, ꢁ4.3, ꢁ4.4 ; IR (neat) 3706, 3049, 2932, 2859, 1252,
1113 cmꢁ1; HRMS (ESI) m/z calcd for C32H50NaO5Si2 (M+Na)+
593.3094, found 593.3098.
oil (105.0 mg, 91%): Rf = 0.50 (60% EtOAc/hexanes); [
a
]
25 = ꢁ1.7 (c
D
0.1, CHCl3); 1H NMR (300 MHz, CDCl3) d 7.75–7.64 (m, 4H),
7.47–7.30 (m, 6H), 7.05 (dd, J = 15.6, 5.1 Hz, 1H), 6.03 (dd, J = 15.6,
1.2 Hz, 1H), 5.86 (ddd, J = 17.4, 10.2, 7.5 Hz, 1H), 4.92 (d,
J = 10.2 Hz, 1H), 4.77 (d, J = 17.4 Hz, 1H), 4.43 (app t, J = 4.8 Hz,
1H), 4.24 (dd, J = 7.5, 3.0 Hz, 1H), 4.11 (dd, J = 7.2, 4.8 Hz, 1H), 3.89
(dd, J = 7.2, 3.0 Hz, 1H), 1.41 (s, 3H), 1.35 (s, 3H), 1.07 (s, 9H), 0.89
(s, 9H), 0.07 (s, 3H), 0.05 (s, 3H); 13C NMR (75 MHz, CDCl3) d 171.5,
150.0, 137.1, 136.1, 136.0, 134.0, 133.4, 129.8, 129.6, 127.6, 127.4,
121.6, 117.2, 109.7, 81.4, 79.4, 75.3, 72.9, 27.5, 27.2, 27.1, 25.9,
19.5, 18.2, ꢁ4.4, ꢁ4.6; IR (thin film) 3074, 2957, 2932, 2859, 1701,
1658 cmꢁ1; HRMS (ESI) m/z calcd for C34H50NaO6Si2 (M+Na)+
633.3044, found 633.3047.
4.2.7. (S)-2-(tert-Butyldimethylsilyloxy)-2-((4S,5S)-5-((S)-1-(tert-
butyldiphenylsilyloxy)allyl)-2,2-dimethyl-1,3-dioxolan-4-yl)ace-
taldehyde 6
To a solution of alcohol 14 (979 mg, 1.71 mmol) in CH2Cl2
(23 mL) was added (diacetoxyiodo)benzene (586 mg, 1.82 mmol),
followed by TEMPO (89.8 mg, 0.566 mmol). The reaction mixture
was then stirred under atmosphere of argon at room temperature
for 16 h. The mixture was quenched with 20 mL of saturated aque-
ous NH4Cl:brine (1:1). The aqueous layer was extracted with
CH2Cl2 (3 ꢂ 20 mL). The combined organic layers were washed
with brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. Purification of the crude residue by column chromatogra-
phy (hexanes–2% EtOAc/hexanes) afforded the title compound as
a colorless oil (933 mg, 95%): Rf = 0.50 (10% EtOAc/hexanes);
4.2.10. (R,E)-((S)-Hept-6-en-2-yl)4-(tert-butyldimethylsilyloxy)-4-
((4S,5S)-5-((S)-1-(tert-butyl-diphenylsilyloxy)allyl)-2,2-dimethyl-
1,3-dioxolan-4-yl)but-2-enoate 16
25 = ꢁ3.7 (c 0.1, CHCl3); 1H NMR (300 MHz, CDCl3) d 9.65 (s,
To a solution of carboxylic acid 5 (226 mg, 0.370 mmol) in
[
a]
D
toluene (2.3 mL) was added triethylamine (155
followed by 2,4,6-trichlorobenzoyl chloride (87.0
The solution was stirred under an argon atmosphere at room
temperature for 1.5 h before (S)-hept-6-en-2-ol (42.5 mg,
lL, 1.11 mmol),
1H), 7.77–7.64 (m, 4H), 7.47–7.32 (m, 6H), 5.82 (ddd, J = 17.4,
10.5, 6.6 Hz, 1H), 5.01 (d, J = 10.5 Hz, 1H), 4.91 (d, J = 17.4 Hz,
1H), 4.32 (dd, J = 6.6, 3.3 Hz, 1H), 4.29–4.17 (m, 3H), 1.35 (s, 3H),
1.34 (s, 3H), 1.10 (s, 9H), 0.93 (s, 9H), 0.12 (s, 3H), 0.11 (s, 3H);
13C NMR (75 MHz, CDCl3) d 202.7, 136.1, 133.7, 133.2, 129.8,
129.6, 127.5, 127.4, 117.7, 109.2, 79.4, 78.1, 78.0, 74.7, 27.1, 27.0,
25.8, 19.4, 18.3, ꢁ4.6, ꢁ4.7; IR (thin film) 2932, 2859, 1738,
lL, 0.556 mmol).
4
0.372 mmol) and DMAP (54.4 mg, 0.445 mmol) were added. The
reaction mixture was stirred at room temperature for 3 h. The mix-
ture was quenched with saturated aqueous NaHCO3 (3 mL). The
aqueous layer was extracted with EtOAc (5 ꢂ 5 mL). The combined
organic layers were washed with brine, dried over Na2SO4, and con-
centrated in vacuo. Purification of the crude residue by column chro-
matography (5% EtOAc/hexanes) yielded the title compound as a
light yellow oil (228 mg, 87%): Rf = 0.74 (20% EtOAc/hexanes);
1254, 1113 cmꢁ1
; HRMS (ESI) m/z calcd for C32H48NaO5Si2
(M+Na)+ 591.2938, found 591.2940.
4.2.8. (R,E)-Ethyl 4-(tert-butyldimethylsilyloxy)-4-((4S,5S)-5-((S)-
1-(tert-butyldiphenyl-silyloxy)allyl)-2,2-dimethyl-1,3-dioxolan-
4-yl)but-2-enoate 15
[a]
25 = +2.4 (c 0.1, CHCl3); 1H NMR (300 MHz, CDCl3) d 7.69 (app d,
D
J = 7.5 Hz, 4H), 7.47–7.30 (m, 6H), 6.89 (dd, J = 15.6, 5.4 Hz, 1H),
5.97 (app d, J = 15.6 Hz, 1H), 5.92–5.71 (m, 2H), 5.92–5.71 (m, 4H),
4.82–4.71 (m, 1H), 4.36 (app t, J = 5.4 Hz, 1H), 4.25 (dd, J = 7.5,
3.3 Hz, 1H), 4.09 (dd, J = 7.2, 5.1 Hz, 1H), 3.90 (dd, J = 7.2, 3.3 Hz,
1H), 2.07 (q, J = 6.9 Hz, 2H), 1.70–1.40 (m, 4H), 1.39 (s, 3H), 1.35 (s,
3H), 1.26 (d, J = 6.3 Hz, 3H), 1.07 (s, 9H), 0.88 (s, 9H), 0.06 (s, 3H),
0.03 (s, 3H); 13C NMR (75 MHz, CDCl3) d 165.7, 146.8, 138.4, 137.1,
136.1, 136.0, 134.1, 133.6, 129.7, 129.5, 127.5, 127.3, 122.9, 117.1,
114.7, 109.7, 81.6, 79.7, 75.6, 73.3, 70.9, 35.4, 33.5, 27.5, 27.3, 27.1,
25.9, 24.6, 20.0, 19.5, 18.2, ꢁ4.4, ꢁ4.6; IR (thin film) 3074, 2932,
To a solution of aldehyde 6 (913 mg, 1.60 mmol) in CH2Cl2
(18 mL) at room temperature was added (carbethoxymethylene)
triphenylphosphorane (1.11 g, 3.19 mmol) in one portion. The reac-
tion mixture was then stirred under Ar at room temperature for 4 h,
after which the solvent was removed and the crude residue was
purified by column chromatography (hexanes–2% EtOAc/hexanes)
to give
a,b-unsaturated ester 15 as a light yellow oil (916 mg,
90%): Rf = 0.47 (10% EtOAc/hexanes); [
NMR (300 MHz, CDCl3) d 7.78–7.64 (m, 4H), 7.47–7.30 (m, 6H),
a
]
D
25 = ꢁ2.7 (c 0.1, CHCl3); 1H
6.94 (dd, J = 15.6, 5.1 Hz, 1H), 6.01 (dd, J = 15.6, 1.5 Hz, 1H), 5.86
Please cite this article in press as: Tadpetch, K.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.06.020

6
K. Tadpetch et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
2859, 1721, 1255 cmꢁ1; HRMS (ESI) m/z calcd for C41H62NaO6Si2
4.2.13. Macrolactone 1
(M+Na)+ 729.3983, found 729.3986.
To a solution of acetonide 17 (24.5 mg) in THF (3.9 mL) was
added 2 M HCl (3.8 mL). The reaction mixture was then stirred at
room temperature for 5 h. The mixture was quenched with satu-
rated aqueous NaHCO3 (8 mL). The aqueous layer was extracted
with EtOAc (8 ꢂ 10 mL). The combined organic layers were washed
with brine and concentrated in vacuo. The crude product was puri-
fied by column chromatography (80% EtOAc/hexanes) to give
macrolactone 1 as a white solid (15.0 mg, 70%): Rf = 0.57 (20%
4.2.11. (R,E)-((S)-Hept-6-en-2-yl)4-hydroxy-4-((4R,5R)-5-((S)-1-
hydroxyallyl)-2,2-dimethyl-1,3-dioxolan-4-yl)but-2-enoate 3
To a solution of silyl ether 16 (278.7 mg, 0.323 mmol) in THF
(4 mL) at 0 °C was slowly added TBAF (1.0 M solution in THF,
1.29 mL, 1.29 mmol). The reaction mixture was stirred under
an argon atmosphere from 0 °C to room temperature for 3 h.
The solution was quenched with H2O (5 mL). The aqueous layer
was extracted with EtOAc (3 ꢂ 5 mL). The combined organic
layers were washed with brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was purified by column
chromatography (15–20% EtOAc/hexanes) to give the title com-
MeOH/CH2Cl2); mp 118–120 °C; [
a]
25 = ꢁ127.6 (c 0.15, CHCl3);
D
1H NMR (300 MHz, CDCl3) d 6.86 (dd, J = 15.6, 3.6 Hz, 1H), 6.19
(d, J = 15.6 Hz, 1H), 5.63–5.51 (m, 1H), 5.51–5.39 (m, 1H), 5.07–
4.04 (m, 1H), 4.69–4.55 (m, 1H), 4.32 (d, J = 7.8 Hz, 1H), 4.03–
3.93 (m,1H), 3.40 (d, J = 4.5 Hz, 1H), 2.25–2.07 (m, 1H), 1.98–1.86
(m, 1H), 1.86–1.72 (m, 1H), 1.62–1.52 (m, 1H), 1.52–1.37 (m,
1H), 1.27 (d, J = 6.3 Hz, 3H), 1.09–0.91 (m, 1H); 13C NMR
(75 MHz, CDCl3) d 166.3, 144.6, 132.1, 129.8, 123.8, 73.3, 72.9,
72.4, 72.2, 69.3, 35.5, 29.7, 26.3, 20.8; IR (thin film) 3392, 3018,
pound as
EtOAc/hexanes);
a colorless oil (126.0 mg, 91%): Rf = 0.30 (40%
[
a]
25 = ꢁ71.8 (c 0.1, CHCl3); 1H NMR
D
(300 MHz, CDCl3) d 6.95 (dd, J = 15.6, 4.5 Hz, 1H), 6.10 (dd,
J = 15.6, 1.5 Hz, 1H), 5.88 (ddd, J = 16.8, 10.5, 5.4 Hz, 1H), 5.75
(ddt, J = 16.5, 10.2, 6.3 Hz, 1H), 5.32 (d, J = 17.1 Hz, 1H), 5.22
(d, J = 10.5 Hz, 1H), 5.07–4.98 (m, 2H), 4.40–4.30 (m, 1H),
4.28–4.19 (m, 1H), 4.01 (dd, J = 7.5, 3.6 Hz, 1H), 3.91 (dd,
J = 7.5, 6.3 Hz, 1H), 3.70 (br s, 1H), 3.21 (br s, 1H), 2.03 (q,
J = 6.9 Hz, 2H), 1.64–1.40 (m, 4H), 1.39 (s, 6H), 1.21 (d,
2975, 2930, 1714, 1261 cmꢁ1
14H22NaO6 (M+Na)+ 309.1314, found 309.1314.
; HRMS (ESI) m/z calcd for
C
Acknowledgements
This work was financially supported by The Thailand Research
Fund (Grant No. MRG5680028), Office of the Higher Education
Commission and Prince of Songkla University. Center of
Excellence for Innovation in Chemistry (PERCH-CIC) is acknowl-
edged for partial support. Additional support is generously pro-
vided by the Development and Promotion of Science and
Technology Talents Project (DPST) for L. Jeanmard.
J = 6.3 Hz, 3H); 13C NMR (75 MHz, CDCl3)
d 166.1, 145.7,
138.4, 136.6, 122.2, 116.9, 114.8, 109.8, 80.8, 78.7, 71.4, 35.3,
33.4, 27.1, 24.6, 19.9; IR (thin film) 3376, 3078, 2985, 2936,
1715, 1271 cmꢁ1
;
HRMS (ESI) m/z calcd for C19H30NaO6
(M+Na)+ 377.1940, found 377.1936.
4.2.12. (3aR,4R,5E,9S,13Z,15S,15aR)-4,15-Dihydroxy-2,2,9-tri-
methyl-9,10,11,12,15,15a-hexahydro-3aH-[1,3]dioxolo[4,5-f][1]-
oxacyclotetradecin-7(4H)-one 17
References
1. (a) Chu, D. T. W. Expert Opin. Invest. Drugs 1995, 4, 65–94; (b) Zhanel, G. G.;
Dueck, M.; Hoban, D. J.; Vercaigne, L. M.; Embil, J. M.; Gin, A. S.; Karlowsky, J. A.
Drugs 2001, 61, 443–498; (c) Zhanel, G. G.; Walters, M.; Noreddin, A.;
Vercaigne, L. M.; Wierzbowski, A.; Embil, J. M.; Gin, A. S.; Douthwaite, S.;
Hoban, D. J. Drugs 2002, 62, 1771–1804.
A solution of diene 3 (30.7 mg, 86.6
was purged with argon over 10 min after which Grubbs 1st gener-
ation catalyst (35.7 mg, 43.3 mol) was added in one portion at
lmol) in CH2Cl2 (87 mL)
l
room temperature. The reaction mixture was heated at 40 °C for
14 h before being cooled to room temperature and concentrated
in vacuo. The crude mixture was purified by column chromatogra-
phy (20% EtOAc/hexanes) to give the title compound as a light yel-
low oil (7.1 mg, 35% based on 8.7 mg of recovered 3): Rf = 0.27 (40%
2. Rukachaisirikul, V.; Rodglin, A.; Phongpaichit, S.; Buatong, J. Phytochem. Lett.
2012, 5, 13–17.
3. Zhou, Y.; Murphy, P. V. Org. Lett. 2008, 10, 3777–3780.
4. Zhu, J.; Ma, D. Angew. Chem., Int. Ed. 2003, 42, 5348–5351.
5. Ramesh, P.; Meshram, H. M. Tetrahedron Lett. 2012, 53, 4008–4011.
6. Zheng, J.; Ma, J.; Xiang, S.; Cai, S.; Liu, X.-W. Angew. Chem., Int. Ed. 2013, 52,
5134–5137.
7. Inanaga, J.; Hirata, K.; Saeki, H.; Katsuki, T.; Yamaguchi, M. Bull. Chem. Soc. Jpn.
1979, 52, 1989–1993.
8. Conrad, J. C.; Fogg, D. E. Curr. Org. Chem. 2006, 10, 185–202.
9. (a) Díaz-Oltra, S.; Angulo-Pachón, C. A.; Murga, J.; Falomir, E.; Carda, M.; Marco,
J. A. Chem. Eur. J. 2011, 17, 675–688; (b) Bali, A. K.; Sunnam, S. K.; Prasad, K. R.
Org. Lett. 2014, 16, 4001–4003.
EtOAc/hexanes); [
a]
25 = ꢁ69.6 (c 0.1, CHCl3); 1H NMR (300 MHz,
D
CDCl3) d 6.80 (dd, J = 15.6, 2.4 Hz, 1H), 6.27 (dd, J = 15.6, 2.4 Hz,
1H), 5.62 (dt, J = 10.5, 7.5 Hz, 1H), 5.48 (dd, J = 10.5, 9.3 Hz, 1H),
5.18–5.05 (m, 1H), 4.82–4.74 (m, 1H), 4.35–4.23 (m, 2H), 3.80 (d,
J = 8.4 Hz, 1H), 2.78 (br s, 1H), 2.10–1.97 (m, 2H), 1.93–1.80 (m,
1H), 1.80–1.45 (m, 2H), 1.50 (s, 3H), 1.46 (s, 3H), 1.30 (d,
J = 6.6 Hz, 3H), 1.20–1.07 (m, 1H); 13C NMR (75 MHz, CDCl3) d
165.2, 141.4, 132.7, 129.9, 122.8, 110.9, 78.2, 78.0, 71.4, 67.4,
65.3, 33.9, 28.8, 27.3, 27.2, 24.9, 20.1; IR (thin film) 3483, 2934,
10. (a) Fürstner, A. Top. Catal. 1997, 4, 285–299; (b) Gradillas, A.; Pérez-Castells, J.
Angew. Chem., Int. Ed. 2006, 45, 6086–6101.
11. (a) Kanematsu, M.; Yoshida, M.; Shishido, K. Angew. Chem., Int. Ed. 2011, 50,
2618–2620; (b) Dermenci, A.; Selig, S. S.; Domaoal, R. A.; Spasov, K. A.;
Anderson, K. S.; Miller, S. J. Chem. Sci. 2011, 2, 1568–1572; (c) Sunnam, S. K.;
Prasad, K. R. Tetrahedron 2014, 70, 2096–2101; (d) Ramakrishna, K.; Kaliappan,
K. P. Org. Biomol. Chem. 2015, 13, 234–240.
2936, 1716, 1374, 1262 cmꢁ1
17H26NaO6 (M+Na)+ 349.1627, found 349.1627.
; HRMS (ESI) m/z calcd for
C
Please cite this article in press as: Tadpetch, K.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.06.020