Conformationally constrained goniofufurone mimics as inhibitors of tumour cells growth: Design, synthesis and SAR study

Article abstract of DOI:10.1016/j.ejmech.2014.05.081

Synthesis of conformationally restricted (+)-goniofufurone (1) and 7-epi-(+)-goniofufurone (2) analogues, with embedded O-isopropylidene, O-methylidene or cyclic carbonate functions is disclosed starting from d-glucose. A number of potential bioisosteres

Full text of DOI:10.1016/j.ejmech.2014.05.081

Accepted Manuscript
Conformationally constrained goniofufurone mimics as inhibitors of tumour cells
growth: design, synthesis and SAR study
Goran Benedeković , Jovana Francuz , Ivana Kovačević , Mirjana Popsavin , Bojana
Srećo Zelenović , Vesna Kojić , Gordana Bogdanović , Vladimir Divjaković , Velimir
Popsavin
PII:
S0223-5234(14)00513-3
10.1016/j.ejmech.2014.05.081
EJMECH 7039
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 2 April 2014
Revised Date: 27 May 2014
Accepted Date: 31 May 2014
Please cite this article as: G. Benedeković, J. Francuz, I. Kovačević, M. Popsavin, B.S. Zelenović, V.
Kojić, G. Bogdanović, V. Divjaković, V. Popsavin, Conformationally constrained goniofufurone mimics
as inhibitors of tumour cells growth: design, synthesis and SAR study, European Journal of Medicinal
Chemistry (2014), doi: 10.1016/j.ejmech.2014.05.081.
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ACCEPTED MANUSCRIPT
Graphycal Abstract
Conformationally constrained goniofufurone mimics as inhibitors of tumour cells
growth: design, synthesis and SAR study
a
a
a
a
Goran Benedeković , Jovana Francuz , Ivana Kovačević , Mirjana Popsavin , Bojana Srećo
a
b
b
c
a
Zelenović , Vesna Kojić , Gordana Bogdanović , Vladimir Divjaković , Velimir Popsavin
a
Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences,
University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia
b
Oncology Institute of Vojvodina, Put doktora Goldmana 4, 21204 Sremska Kamenica, Serbia
c
Department of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 4,
21000 Novi Sad, Serbia

ACCEPTED MANUSCRIPT
Conformationally constrained goniofufurone mimics as inhibitors of
tumour cells growth: design, synthesis and SAR study
a
a
a
a
Goran Benedeković , Jovana Francuz , Ivana Kovačević , Mirjana Popsavin , Bojana Srećo
a
b
b
c
a,
Zelenović , Vesna Kojić , Gordana Bogdanović , Vladimir Divjaković , Velimir Popsavin *
a
Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences,
University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia
b
Oncology Institute of Vojvodina, Put doktora Goldmana 4, 21204 Sremska Kamenica, Serbia
c
Department of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 4,
21000 Novi Sad, Serbia
Abstract
Synthesis of conformationally restricted (+)-goniofufurone (1) and 7-epi-(+)-goniofufurone (2)
analogues, with embedded O-isopropylidene, O-methylidene or cyclic carbonate functions is
disclosed starting from D-glucose. A number of potential bioisosteres of 1 and 2 bearing both 5,7-O-
methylidene and 4-substituted cinnamoyloxy functions at the C-7 position have also been
synthesized. In vitro cytotoxicity of target molecules against a number of human tumour cell lines
were recorded and compared with those observed for the parent molecules 1 and 2. Some of the
analogues displayed powerful antiproliferative effects on selected human tumour cell lines, but all
of them were devoid of any cytotoxicity towards the normal foetal lung fibroblasts (MRC-5). A
SAR study reveals the structural features of these lactones that may increase their antiproliferative
activity.
Keywords: styryl lactone, goniofufurone, conformational constrain, isosterism, antitumour activity,
structure-activity relationships
*
Corresponding author. Tel.: +381 21 485 27 68; fax: +381 21 454 065. E-mail address: velimir.popsavin@dh.uns.ac.rs
(
V. Popsavin).
1

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1. Introduction
(+)-Goniofufurone (1; Scheme 1) and 7-epi-(+)-goniofufurone (2) are naturally occurring styryl
lactones that have attracted considerable attention since their isolation from the stem bark of
Goniothalamus giganteus (Annonaceae) [1,2]. Their structures were elucidated by spectroscopic
methods, and the relative configurations were determined by X-ray crystallography. The absolute
configurations were established independently by Shing [3–5] and Jäger [6,7] from the syntheses of
their opposite enantiomers, (−)-goniofufurone and 7-epi-(−)-goniofufurone, respectively. Due to
their unique structural features and promising antitumour activities [8–11], both natural products 1
and 2, along with a number of their analogues have been the targets of many total syntheses [12–
14]. The development of practical and efficient routes for the synthesis of analogues of naturally
occurring compounds is of considerable interest for drug design and discovery. More potent
analogues can be designed by manipulation of functional groups, stereochemistry or by introduction
of a conformational constrain.
Scheme 1
We have recently demonstrated that the embedment of an oxetane ring increases the antitumour
potency originally displayed by lead 1 [15]. On the other hand, a study carried out previously in our
laboratory shows that dephenylated analogues of 1, and in particular the corresponding (3S,4R)-
stereoisomer strongly inhibits the growth of certain human neoplastic cell lines [16]. Based on the
above mentioned observations, we have planned the synthesis of tricyclic lactones of type 3 and 4
that represent conformationally constrained analogues of 1 and 2, annelated with 1,3-dioxane or 2-
substituted 1,3-dioxane heterocyclic rings. Furthermore, a series of new goniofufurone and 7-epi-
goniofufurone bioisosteres of type 5 and 6 has been designed by combining both ring insertion and
isosterism methods. Apparently, the structures 5 and 6 were formally obtained by isosteric
replacement of the phenyl ring in 3 and 4 respectively with a cinnamoyloxy function, or with
substituted cinnamate residues bearing an electron-withdrawing (F, NO ) or electron-donating
2
(OMe) substituents in the C-4 position. Special interest in the cinnamic acid ester group is
associated with its presence in several naturally occurring styryl lactones that were isolated from the
tropical plant Polyalthia crassa [17] and found to exhibit a potent and selective cytotoxicity against
some human tumour cell lines [15, 17–19]. In addition to the synthesis of analogues 3–6, simple
and efficient routes to (+)-goniofufurone (1) and 7-epi-(+)-goniofufurone (2) have been developed
in order to provide samples of the leads that would serve as control molecules in antitumour assays.
2

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Furthermore, styryl lactones 1 and 2 represent possible starting materials for the preparation of
conformationally restricted analogues 3 and 4.
2. Results and discussion
2.1. Chemistry
Preparation of 1 and 2 started from alcohols 7 or 8, which are readily available from D-glucose
through a modified literature procedure [20,21] (Scheme 2). For the sake of synthesis of 2,
compound 7 was first converted to the corresponding di-O-benzyl ether 9a by treatment with benzyl
bromide and sodium hydride in N,N-dimethylformamide. Hydrolytic removal of the isopropylidene
protective group in 9a with aqueous trifluoroacetic acid gave the expected lactol 9b. Subsequent
treatment of 9b with Meldrum’s acid in DMF in the presence of triethylamine, followed by final
hydrogenolytic 5,7-di-O-deprotection furnished the natural product 2. 7-epi-(+)-Goniofufurone (2)
was thus prepared from 7 in an overall yield of 39%, over the four steps and a single
chromatographic purification. Slightly better overall yield (48%) was obtained by using the
compound 8 as a starting material.
Scheme 2
Next, we started a two-step synthetic sequence leading to the natural product 1. Thus a selective
oxidation of the benzylic alcohol function in 2 under the Hunsen conditions [22], first gave the
corresponding ketone 10 in an almost quantitative yield. Subsequent reduction of the carbonyl
group in 10 with NaBH in the presence of L-tartaric acid [23] gave a 5:1 mixture of diastereomers,
4
which after chromatographic separation furnished target 1 as the major product in 81% yield. All
physical constants and spectroscopic data of thus prepared natural products 1 and 2 were in full
agreement with those reported previously [15,21].
Preparation of conformationally constrained analogues of (+)-goniofufurone and 7-epi-(+)-
goniofufurone (compounds 3 and 4) is outlined in Scheme 3.
Scheme 3
The synthesis of 5,7-O-isopropylidene derivatives 3a and 4a was first attempted starting from 1 and
2
, respectively. It is interesting to note that the analogue 3a actually represents a natural product that
was isolated in 2001 from the roots of Goniothalamus cheliensis [24]. Its structure was determined
on the basis of spectral and chemical evidence that included treatment of 1 with 2,2′-
3

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dimethoxypropane in dry acetone and in the presence of a catalytic amount of toluene-4-sulphonic
acid. We applied exactly the same reaction conditions to obtain analogues 3a (from 1) and 4a (from
1
3
2
) both in 95% yield. The physical constants and the C spectral data of thus obtained sample 3a
1
were consistent with those previously reported [24]. However, the published H NMR spectral data
for 3a contain the erroneous assignments for H-5 and H-7 whose chemical shifts should be
interchanged (for the comparison of NMR spectra, see Table S5 in the Supplementary data). The
authors have probably been confused by a large vicinal coupling between H-6 and H-7 (8.1 Hz)
which is inconsistent with a chair-like geometry of the six-membered ring but points to the anti
arrangement of these protons. This is possible only if the six-membered ring occupies a twist-boat
conformation with a pseudo-axially oriented H-7 atom, as confirmed by a NOE experiment.
Namely, it was found that when the H-3 signal was irradiated, the H-7 peak was enhanced,
suggesting that these protons have a syn orientation that means the phenyl group is pseudo-
equatorially oriented. The single crystal X-ray analysis of 3a, confirmed the twist-boat geometry of
the six-membered ring (Figure 1), as well as the anti (trans-diaxial) arrangement of H-6 and H-7 (τ
=
167.2 °), which is consistent with the observed vicinal couplings of 8.1 Hz. Finally, the distance
between H-3 and H-7 (3.05 Å) is consistent with NOE results.
Figure 1
Twist-boat geometry of the six-membered ring in 3a is not entirely unexpected, because the
alternative chair-like conformation would be destabilized by strong 1,3-diaxial clashes of bulky Ph
and Me groups. In contrast, a relatively small vicinal coupling between H-6 and H-7 (1.7 Hz) was
1
observed in the H NMR spectrum of 7-epimer 4a, and no NOE contacts between non-contiguous
H-atoms were detected. These findings are consistent with a gauche arrangement of H-6 and H-7,
with the phenyl group in equatorial position, and with the six-membered ring occupying a chair-like
conformation.
Methylene acetals were first prepared by treatment of alcohols 1 and 2 with para-formaldehyde and
toluene-4-sulfonic acid in anhydrous CH CN at room temperature, following a slightly modified
3
literature procedure [25]. Acetalisation of natural compound 1 gave two products: 1,3-dioxane 3b
(48%) and 1,3,5-trioxaepane 3c (49%). In this case the exclusive formation of the dioxane
derivative has been probably hampered by sterical crowding due to the 1,3-diaxial repulsion of Ph
and H in the six-membered ring, while the formation of trioxaepane 3c bearing the equatorial
phenyl group is also favourable from the sterical reasons. However, methylidenation of 2 under the
same reaction conditions exclusively gives the expected 5,7-O-methylidene derivative 4b in 82%
4

ACCEPTED MANUSCRIPT
yield. No derivative with 1,3,5-trioxaepane function has been obtained thus demonstrating the
easier formation of the 1,3-dioxane cycle, evidently by sterical reasons. Stereochemistry of
methylene acetals 3b, 3c and 4b were confirmed by single crystal X-ray diffraction analysis (for the
crystal structures of 3b, 3c and 4b, see the Supplementary data). Methylidenation of both natural
compounds 1 and 2 was also attempted by using an adopted procedure [26] that involved their
treatment with SOCl in dry DMSO at 65 °C. Under these reaction conditions compound 1 again
2
gave a mixture of 3b (38%) and 3c (51%), while acetalisation of 2 solely gave the corresponding
5,7-O-methylidene derivative 4b in 95% yield.
Finally, treatment of 1 and 2 with 1,1′-carbonyldiimidazole in anhydrous CH CN at 46–48 °C gave
3
the expected cyclic carbonates 3d and 4c in 96 and 73% yield, respectively. The structure and purity
of thus obtained products 3d and 4c was confirmed on the basis of spectroscopic data, and their
stereochemical integrity was confirmed by X-ray analysis (for the crystal structure of 3d and 4c, see
the Supplementary data).
The synthesis of cinnamic isosteres 5 and 6 commenced with the preparation of hemiacetal 12
(Scheme 4).
Scheme 4
As previously reported the reaction between lead tetraacetate [27] or sodium periodate [28] and 1,2-
O-isopropylidene-α- -glucofuranose (11a) gave 3,5-O-methylene derivative 12a as the main
D
reaction product. Accordingly, we assumed that lactone 11 [29] under similar conditions may give
the desired intermediate 12. It was subsequently shown that treatment of 11 with periodic acid in
dry acetonitrile indeed gives 12 in 80% yield. Pure product 12 was isolated by flash column
chromatography as a mixture of (7S)- and (7R)-stereoisomers. However, the slow crystallization
from a mixture of acetone and hexane afforded pure (7S)-isomer in the form of colourless needles
of X-ray quality (for the crystal structure of 12, see the Supplementary data). The single crystal X-
ray diffraction analysis of 12 confirmed a chair-like conformation of the newly formed 1,3-dioxane
ring with the C-7 hemiacetal hydroxyl group in axial (exo) position.
Three independent procedures were used for the conversion of 12 to the cinnamic esters 5 and 6 and
the results are presented in Table 1.
Table 1
5

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In our first experiments, lactone 12 (a mixture of stereoisomers) was treated with cinnamoyl
chloride (entry 1) or with 4-nitrocinnamoyl chloride (entry 4) in the presence of DMAP in dry
acetonitrile, to afford ~2:1 mixtures of 5 and 6 in 86 and 96% combined yields, respectively.
1
13
Interestingly, both H and C NMR spectra of 5a contained the peaks at δ 5.29 (s, 2 H) and δ
H
C
5
3.5 ppm corresponding to a CH Cl molecule in the crystalline sample 5a. This indicated that
2 2
product 5a co-crystallized with the solvent molecule, as confirmed by single crystal X-ray
diffraction analysis (for the crystal structure of 5a, see the Supplementary data).
Next, the esterification step was attempted by using the Steglich esterification protocol [30]. We
were pleased to find that treatment of 12 with 4-fluoro- or 4-methoxycinnamic acid, in the presence
of DCC and DMAP in anhydrous dichloromethane gave the corresponding esters 5b and 5d as the
only reaction products, both in 60% yield (entries 2 and 5). Exclusive formation of (7R)-configured
products is probably a result of thermodynamic control of the process.
Finally, in order to provide an access to the (7S)-configured cinnamic esters 6b and 6d we treated
lactol 12 under the standard Mitsunobu conditions [31]. Thus, when lactone 12 reacted with 4-
fluorocinnamic acid, in the presence of Ph P and DEAD, a ~2:1 mixture of 6b and 5b was obtained
3
in 65% combined yield (entry 3). However, when the same reaction was carried out with 4-
methoxycinnamic acid, a 3.5:1 mixture of 6d and 5d was obtained in 45% combined yield (entry 6).
The lower yield of previous reaction is probably a result of partial decomposition of the products
observed during flash column chromatography. The assignment of (S) stereochemistry at the C-7 in
products 6a–d was confirmed by an NOE interaction between H-5 and H-7, indicating that these
protons are in close proximity on the same side of the ring. This effect was not observed in epimers
5a–d, thus implying the opposite (R) stereochemistry at C-7.
2.2. Biological evaluation and SAR
After completion of the synthesis, analogues 3–6 were evaluated for their in vitro cytotoxicity
against a panel of human malignant cell lines, including myelogenous leukaemia (K562),
+
promyelocytic leukaemia (HL-60), T cell leukaemia (Jurkat), Burkitt’s lymphoma (Raji), ER
−
breast adenocarcinoma (MCF-7), ER breast adenocarcinoma (MDA-MB-231), cervix carcinoma
(
HeLa), melanoma cells (Hs 294T) and against a single normal cell line, foetal lung fibroblasts
MRC-5). Cytotoxic activity was evaluated by using the standard MTT assay, after exposure of
(
cells to the tested compounds for 72 h. (+)-Goniofufurone (1), 7-epi-(+)-goniofufurone (2) and the
commercial antitumour agent doxorubicin (DOX) were used as positive controls.
6

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Table 2
According to the recorded IC values (Table 2), the HL-60, Raji and HeLa cell lines are sensitive
5
0
to all of the synthesized analogues. Remarkably, in the culture of HL-60 cell line, the majority of
synthesized analogues displayed several-fold higher potency when compared to leads 1 and 2. The
highest potency in the culture of these cells was recorded after treatment with 4b (IC 0.24 ꢀM),
5
0
which was approximately 4-fold more active than the commercial drug doxorubicin. All eight (+)-
goniofufurone mimics (3a–5d) demonstrated diverse antiproliferative effects toward HL-60 cells, in
contrast to the lead 1, which was completely inactive against this cell line. With the exception of
analogues 6c and 6d, all of the remaining 7-epi-(+)-goniofufurone mimics were more potent than
lead 2. The most active molecule in the culture of Raji cells is analogue 5a (IC 1.01 ꢀM) that
5
0
exhibited about 18- and 3-fold higher potency than control compounds 1 and DOX, respectively.
On the other hand, 7-epi-(+)-goniofufurone mimics 4a, 4b and 6c showed similar potency as 2 in
this cell line, but were 2- to 3-times more active than the commercial antitumour agent doxorubicin.
The most active compound in the culture of HeLa cells is analogue 5a (IC 1 nM) that exhibited
5
0
over 8300- and 65-fold higher potency when compared to control molecules 1 and DOX,
respectively. (+)-Goniofufurone mimic 5b also exhibited a potent growth inhibitory activity against
HeLa cell line (IC 20 nM). It demonstrated over 400- and 3-fold higher activity than lead 1 and
5
0
DOX (65 nM) in the same cell culture, respectively. The most potent 7-epi-(+)-goniofufurone
mimic toward the HeLa cells is analogue 6a, that exhibited a submicromolar antiproliferative
activity (IC 0.23 ꢀM) against these cells, being essentially 4-fold more potent than the parent
5
0
compound 2. However, comparing to DOX, this analogue exhibited 3.5-fold lower activity against
HeLa cells. The Hs 294T melanoma cells are the least sensitive to most of synthesized lactones,
although the analogue 5b exhibited a potent cytotoxicity (IC 2 nM) being over 2250-fold more
5
0
active than DOX. The parent compound 1 was completely inactive, while 7-epi-(+)-goniofufurone
2) demonstrated a moderate cytotoxicity in the culture of Hs 294T cells. However, the only active
(
analogue of 2 (cinnamate 6a) exhibited 17- and 1.8-fold higher potency than control compounds 2
and DOX, respectively. As the results in Table 2 further illustrate, analogue 4b and lead 2 exhibited
the most pronounced antiproliferative activities against K562 cells (IC 23 nM) being
5
0
approximately10-fold more potent than doxorubicin in the same cell line. Finally, the analogues 3d,
a and 5a, as well as the natural product 2 displayed significant growth-inhibitory activity against
4
all used tumour cell lines except Hs 294T. Remarkably, none of the synthesized styryl lactones nor
the natural products 1 and 2 exhibited toxicity toward the normal MRC-5 cells, in contrast to the
7

ACCEPTED MANUSCRIPT
commercial antitumour agent doxorubicin (DOX) that exhibited potent cytotoxic activity (IC 0.1
5
0
ꢀ
M) against this cell line.
In an attempt to correlate the structures of synthesized goniofufurone mimics with their cytotoxic
activities, we first considered the influence of ring insertion in the structures of leads 1 and 2 [21].
As the data in Table 2 reveal the embedment of 1,3-dioxane or 2-substituted 1,3-dioxane rings
increases the antitumour potency originally displayed by lead 1, but decreases the cytotoxicity
originally demonstrated by lead 2. Replacement of the C-7 phenyl group in 3b and 4b by a
cinnamate moiety caused similar effects. Namely, the cinnamic isosteres of 3b displayed the
increased antitumour potency with respect to that originally displayed by the control molecule 3b,
whereas the same structural changes in 4b gave less active analogues when compared to the
corresponding control. Remarkably, replacement of phenyl ring in compound 3b with
cinnamoyloxy moiety, as in case of compound 5a, produces the most active analogue in this study
which exhibited antitumour activity in a nanomolar range against HeLa cell line (IC 1 nM). The
5
0
next round of modifications aimed at improving the activity was made at the phenyl ring. Therefore,
keeping intact the 3,6-anhydro-2-deoxy-7-C-cinnamoyloxy-5,7-O-methylene- -ido-heptono-1,4-
D
lactone scaffold, selected electron-withdrawing, or electron-donating groups were attached in the
position C-4 of the aromatic ring. Compounds 5a and 6a have been used as control molecules in
this SAR analysis. To our disappointment, the introduction of either electron-withdrawing or
electron-donating groups in the position of C-4 at the aromatic ring of 5a did not improve
antiproliferative activity. However, the introduction of a fluorine atom in the C-4 position produces
the active analogue 5b which exhibited antitumour activity against Hs 294T melanoma cells in a
nanomolar range (IC 2 nM), whereas the introduction of a methoxy group in the same position of
5
0
5
a led to a 120-fold increase in activity against Jurkat cells (IC 42 nM). We finally wanted to
50
explore the effects of absolute stereochemistry at C-7 to antiproliferative activity of analogues. The
importance of this structural feature for the cytotoxic activities was studied by comparing the IC50
values of 1 (7R) and 2 (7S), as well as of seven pairs of analogues (3a and 4a, 3b and 4b, 3d and 4c,
5a and 6a, 5b and 6b, 5c and 6c, 5d and 6d), each of which contains exactly the same substituents
and differs only in their absolute stereochemistry at C-7. As the results shown in Table 2 indicate, in
most cases, the (7S)-configured analogues (4a, 4b and 4c) show an improved cytotoxicity when
compared to the stereoisomers of (7R)-series (3a, 3b and 3d). These results are consistent with our
previous findings [32], which indicated that the styryl lactones having the (7S)-stereochemistry
represent more potent cytotoxic agents with respect to the corresponding (7R)-epimers. However,
the considerations of the same structural feature in the cinnamic isosteres 5 and 6 reveals that (7R)-
8

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stereoisomer 5a exhibits the higher potency than (7S)-epimer 6a against the majority of tumour
cells under evaluation. The remaining (7R)-configured cinnamic bioisosteres (5b–d) show more
potent cytotoxicities with respect to their counterparts of (7S)-series (6b–d) against four of eight
tested tumour cell lines.
3. Conclusions
In summary, fifteen analogues of natural styryl lactones (+)-goniofufurone (1) and 7-epi-(+)-
goniofufurone (2) were designed, synthesized and evaluated in this work. The analogues were
designed by combining two different techniques, such as ring insertion and isosterism.
The newly synthesized compounds were tested in vitro toward a panel of human tumour cell lines,
and the preliminary structure-activity relationships are briefly discussed. Some of the synthesized
compounds showed potent antitumour activity, especially analogues 5a (IC 1 nM against HeLa)
50
and 5b (IC 2 nM against HS 294T) which displayed the highest activity of all molecules under
5
0
evaluation.
The preliminary SAR analysis suggested the following general structural requirements for the anti-
proliferative action of synthesized (+)-goniofufurone mimics: (A) the presence of an additional 1,3-
dioxane or 2-substituted 1,3-dioxane ring increases the antitumour potency originally displayed by
lead 1, but decreases the cytotoxicity originally demonstrated by lead 2; (B) the replacement of
phenyl group at C-7 in 3b by cinnamoyloxy functionalities increases antitumour potency relative to
the control molecule 3b, whereas the same structural changes in lead 4b gave less active analogues;
(C) the heteroannelated styryl lactones having the (7S)-stereochemistry represent more potent
cytotoxic agents than the corresponding (7R)-epimers, whereas the (7R)-configured cinnamic
bioisosteres exhibits the increased antitumour potency when compared to the corresponding (7S)-
isomers.
4. Experimental section
4.1. General experimental procedures
Melting points were determined on a Büchi 510 apparatus and were not corrected. Optical rotations
were measured on an Autopol IV (Rudolph Research) polarimeter at room temperature. NMR
spectra were recorded on a Bruker AC 250 E instrument and chemical shifts are expressed in ppm
downfield from TMS. IR spectra were recorded with an FTIR Nexus 670 spectrophotometer
(Thermo-Nicolet). High resolution mass spectra (ESI) of synthesized compounds were acquired on
9

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an Agilent technologies 6210 TOF LC/MS instrument (LC series 1200). Flash column
chromatography was performed using Kieselgel 60 (0.040–0.063, E. Merck). All organic extracts
were dried with anhydrous Na SO . Organic solutions were concentrated in a rotary evaporator
2
4
under reduced pressure at a bath temperature below 30 °C.
.1.1. 7-epi-(+)-Goniofufurone (2)
4
To a cooled (0 °C) and stirred solution of 8 [20] (1.0 g, 2.81 mmol) in dry DMF (20 mL) were
added successively 95% NaH (0.202 g, 8.43 mmol) and BnBr (0.44 mL, 3.65 mmol). The mixture
was stirred at 0 °C for 0.5 h and then at room temperature for 1.5 h. Absolute MeOH (8 mL) was
finally added, and the mixture was stirred at room temperature for the additional 20 min and
evaporated. The residue was suspended in water (200 ml) and extracted with EtOAc (3×50 mL).
The combined organic solutions were dried and evaporated. The remaining crude 9a was dissolved
in 50% TFA (20 mL) and the resulting solution was stirred for 18 h at room temperature. The
mixture was concentrated by co-distillation with toluene and the resulting crude 9b was dried in
vacuum for 2 h. To a solution of crude 9b in dry DMF (25 mL) was added Meldrum’s acid (0.809
g, 5.61 mmol) and dry Et N (0.8 mL, 5.8 mmol). The mixture was stirred for 66 h at 44–46 °C and
3
evaporated. The residue was suspended in 10% NaCl (200 ml) and extracted with EtOAc (3×50
mL). The organic solutions were combined, dried and evaporated. A solution of crude 9c (1.35 g) in
MeOH (40 mL) was hydrogenated over 10% Pd/C (0.3 g; the catalyst contained 50% of water).
After 24 h an additional amount of catalyst was added (0.3 g) and the hydrogenation was continued
for additional 24 h. The mixture was filtered through a Celite pad and the catalyst washed with
MeOH. The combined organic solutions were evaporated and the residue was purified by flash
chromatography (19:1 CH Cl /MeOH) to afford pure 2 (0.336 g, 48% from 8) as a colourless solid.
2
2
20
Recrystallization from Me CO/hexane gave colourless powder, mp 207–210 °C, [α] +104.7 (c
2
D
2
0
0
.75, EtOH), lit. [15] mp 197–200 °C, (from Me CO/light petroleum), [α] +108.5 (c 0.75, EtOH),
2
D
20
lit. [33] mp 200–203 °C, [α] +102.0 (c 0.5, EtOH), for (−)-enantiomer: lit. [15] mp 205–206 °C
D
2
0
1
13
(
from EtOAc/hexane), [α] −98.3 (c 0.5, acetone), R =0.19 (7:3 CH Cl /EtOAc). IR, H and C
D
f 2 2
NMR spectroscopic data of thus prepared natural product 2 matched those previously reported by us
+
[
15,21]. HRMS (ESI): m/z 268.1177 (M +NH ), calcd for C H NO : 268.1180.
4
13 18
5
4.1.2. 3,6-Anhydro-2-deoxy-7-C-phenyl-L-ido-hept-7-ulosono-1,4-lactone (10)
To a cooled (0 °C) and stirred solution of 2 (0.04 g, 0.16 mmol) and H IO (0.045 g, 0.2 mmol) in
5
6
anhydrous CH CN (5 mL) was added a solution of PCC (0.002 g, 0.009 mmol) in anhydrous
3
1
0

ACCEPTED MANUSCRIPT
CH CN (1 mL) over a period of 1 min. The mixture was stirred at 0 °C for 2 h, then poured into
3
10% aq NaCl (75 mL) and extracted with EtOAc (3×25 mL). The combined organic solutions were
evaporated and the residue was purified by flash column chromatography (47:2:1
CH Cl /MeOH/Me CO) to afford pure 10 (0.038 g, 96%) as a colourless solid. Recrystallization
2
2
2
20
from Me CO/hexane gave colourless crystals, mp 198−201°C, [α] +31.2 (c 0.5, Me CO); R =0.46
2
D
2
f
1
(
(
(
EtOAc). IR (CHCl ): νmax 3411 (OH), 1798 (C=O, lactone), 1681 (PhC=O), 1600 (Ph). H NMR
3
acetonitrile-d ): δ 2.98 (m, 2 H, OH and H-2a), 3.01 (dd, 1 H, J2a,2b=18.6, J2b,3=5.6 Hz, H-2b), 4.97
3
br d, 2 H, H-4 and H-5), 5.20 (dd, 1 H, J =4.4, J =5.1 Hz, H-3), 5.69 (t, 1 H, J =J =4.4 Hz,
3
,4
2b,3
5,6
6,7
13
H-6), 7.56–7.56 (m, 5 H, Ph). C NMR (acetonitrile-d ): δ 36.8 (C-2), 76.5 (C-5), 78.8 (C-3), 85.2
3
(C-6), 89.3 (C-4), 128.9, 129.6, 134.3, 136.8 (Ph), 176.7 (C-1), 196.1 (PhC=O). HRMS (ESI): m/z
+
2
71.0572 (M +Na), calcd for C H NaO : 271.0577.
1
3
12
5
4.1.3. (+)-Goniofufurone (1)
To a suspension of
L-tartaric acid (0.324 g, 0.22 mmol) in dry THF (6 mL) was added NaBH4
(0.084 g, 2.22 mmol) in two equal portions and the suspension was heated at reflux for 2 h before
being cooled to −18 °C. A solution of ketone 10 (0.108 g, 0.42 mmol) in dry THF (10 mL) was
added in two equal portions and the mixture was stirred at −18 °C for 20 h. The mixture was
evaporated with silica gel and the residue was purified on a column of flash silica (Et O for 1, then
2
EtOAc for 2). Eluted first was pure (+)-goniofufurone (0.088 g, 81%) isolated as a colourless solid.
20
Recrystallization from CH Cl /hexane gave colourless powder, mp 149–151 °C, [α] +52.8 (c 0.5,
2
2
D
20
CHCl ), lit. [15] mp 154–155 °C (from EtOAc/hexane), [α] +39.2 (c 0.9, CHCl ), R =0.19 (7:3
3
D
3
f
1
13
CH Cl /EtOAc). IR, H and C NMR spectroscopic data of thus prepared natural product 1
2
2
+
matched those previously reported by us [15,21]. HRMS (ESI): m/z 251.0912 (M +H), calcd for
+
C H O : 251.0914; m/z 273.0736 (M +Na), calcd for C H NaO : 273.0733; m/z 251.0912
13
15
5
13 14
5
+
(
M +H), calcd for C H O : 251.0914. Eluted second was the minor stereoisomer 2 (0.019 g,
13 15 5
17%).
4.1.4. General procedure for O-isopropylidenation of 1 and 2
To a solution of lactones 1 or 2 (1 equiv) in dry Me CO (0.02 M) was added 2,2′-dimethoxypropane
2
(
7 equiv) and TsOH×H O (0.01 equiv). The mixture was stirred at room temperature until the
2
starting materials were consumed (TLC, 3.5 h for 1, 4.5 h for 2). The mixture was neutralized with
0% aq NaHCO and evaporated with silica gel. The residue was purified by flash column
1
3
chromatography (1:1 Et O/hexane).
2
1
1

ACCEPTED MANUSCRIPT
4
.1.4.1. 3,6-Anhydro-2-deoxy-5,7-O-isopropylidene-7-C-phenyl-D-glycero-D-ido-heptono-1,4-
lactone (3a)
20
Yield 95%. Colourless needles, mp 165–166 °C (Et O/hexane), [α] +89.6 (c 0.5, MeOH), lit. [24]
2
D
20
mp 165–166 °C, [α] +80.0 (c 0.05, MeOH); R =0.33 (1:1 Et O/hexane). IR (KBr): ν 1785
D
f
2
max
1
13
(
C=O), 1607 (Ph). For H and C NMR data, see Table S5 in the Supplementary data. HRMS
+
(
ESI): m/z 291.1228 (M +H), calcd for C H O : 291.1227.
1
6
19
5
4.1.4.2. 3,6-Anhydro-2-deoxy-5,7-O-isopropylidene-7-C-phenyl-L-glycero-D-ido-heptono-1,4-
lactone (4a)
2
D
0
Yield 95%. Colourless powder (Et O/hexane, at −10 °C), mp 85 °C (Et O/light petroleum), [α]
2
2
1
+
44.6 (c 0.5, MeOH); R =0.33 (3:2 Et O/hexane). IR (CHCl ): ν 1789 (C=O), 1499 (Ph). H
f 2 3 max
NMR (CDCl ): δ 2.58 (dd, 1 H, J2a,3=1.5, J2a,2b=18.8 Hz, H-2a), 2.67 (dd, 1 H, J2b,3=5.2, J2a,2b=18.8
3
Hz, H-2b), 4.08 (t, 1 H, J =J =2.1 Hz, H-6), 4.67 (br s, 1 H, H-5), 4.69 (d, 1 H, J =4.3 Hz, H-4),
5
,6
6,7
3,4
5
.00 (m, 1 H, J2b,3=5.4, J2a,3=1.6, J =4.1 Hz, H-3), 5.11 (d, 1 H, J =1.8 Hz, H-7), 7.28–7.54 (m, 5
3,4 6,7
1
3
H, Ph). C NMR (CDCl ): δ 29.2 and 29.3 (CMe ) 35.8 (C-2), 70.2 (C-7), 73.2 (C-5), 74.0 (C-6),
3
2
7
2
7.1 (C-3), 86.4 (C-4), 98.8 (CMe ), 126.3, 127.7, 128.2, 137.9 (Ph), 175.3 (C-1). HRMS (ESI): m/z
2
+
91.1218 (M +H), calcd for C H O : 291.1227.
1
6
19
5
4.1.5. General procedure for O-methylidenation of 1 and 2
Procedure A [25]. To a solution of 1 or 2 (1 equiv) in dry CH CN (0.02–0.03 M) was added
3
paraformaldehyde (3 equiv) and TsOH×H O (0.5 equiv). The mixture was stirred at room
2
temperature (20 h for 1, 72 h for 2) then neutralized with solid NaHCO and evaporated with silica
3
gel. The residue was purified by flash column chromatography (99:1 CH Cl /Me CO).
2
2
2
Procedure B [26]. To a stirred solution of 1 or 2 (1 equiv) in dry DMSO (0.06 M) was added SOCl2
14 equiv). The mixture was stirred at 65 °C for 1.5 h, then poured into 10% aq NaCl and extracted
(
with EtOAc. The combined organic solutions were dried and evaporated and the residue was
purified by flash column chromatography (99:1 CH Cl /Me CO).
2
2
2
4.1.5.1. 3,6-Anhydro-2-deoxy-5,7-O-methylidene-7-C-phenyl-D-glycero-D-ido-heptono-1,4-lactone
(3b)
Yield: 48% (Procedure A); 38% (Procedure B). Colourless needles, mp 125 °C (CH Cl /hexane),
2
2
2
D
0
[
α] +182 (c 0.2, CHCl ); R =0.32 (2:3 light petroleum/Et O). IR (film): ν 1789 (C=O), 1497
3 f 2 max
1
2

ACCEPTED MANUSCRIPT
1
(
Ph). H NMR (CDCl ): δ 2.77 (br d, 1 H, J2a,2b=18.7 Hz, H-2a), 2.85 (dd, 1 H, J2a,2b=18.8, J2b,3=5.1
3
Hz, H-2b), 4.47 (t, 1 H, J =J =2.3 Hz, H-6), 4.53 (br s, 1 H, H-5), 4.83 and 4.89 (2×d, 1 H each,
5
,6
6,7
Jgem=6.1 Hz, CH ), 4.99 (d, 1 H, J =4.3 Hz, H-4), 5.10–5.22 (m, 2 H, H-7 and H-3), 7.31–7.51 (m,
2
3,4
1
3
5
4
H, Ph). C NMR (CDCl ): δ 35.9 (C-2), 73.8 (C-7), 75.2 (C-3), 76.5 (C-6), 77.1 (C-5), 86.1 (C-
3
), 86.8 (CH ), 127.5, 128.3, 128.8 and 136.5 (Ph), 175.0 (C-1). HRMS (ESI): m/z 280.1175
2
+
(
M +NH ), calcd for C H NO : 280.1180.
4
14 18
5
4
.1.5.2. 1,3,5-Trioxaepane 3c
Yield: 49% (Procedure A); 51% (Procedure B). Colourless needles, mp 188 °C (CH Cl /hexane),
2
2
2
D
0
[
α] −65.0 (c 0.1, CHCl ); R =0.27 (2:3 light petroleum/Et O). IR (film): ν 1775 (C=O), 1603
3 f 2 max
1
and 1495 (Ph). H NMR (CDCl ): δ 2.57 (br d, 1 H, J2a,2b=18.2 Hz, H-2a), 2.68 (dd, 1 H,
3
J2a,2b=18.6, J2b,3=4.7 Hz, H-2b), 4.26 (dd, 1 H, J =3.4, J =9.1 Hz, H-6), 4.62 (d, 1 H, J =3.4 Hz,
5,6
6,7
5,6
H-5), 4.67 (d, 1 H, J =9.1 Hz, H-7), 4.77 and 4.82 (2×d, 1 H each, J =6.8 Hz , CH -a), 4.92–5.03
6
,7
gem
2
(
m, 2 H, H-3 and H-4), 5.06 and 5.11 (2×d, 1 H each, Jgem=6.8 Hz , CH -b), 7.29–7.46 (m, 5 H, Ph).
2
1
3
C NMR (CDCl ): δ 36.1 (C-2), 77.8 (C-7), 78.0 (C-3), 81.4 (C-5), 83.3 (C-6), 86.9 (C-4), 94.8 and
3
9
4.9 (2×CH ), 127.0, 128.2, 128.4 and 139.5 (Ph), 174.9 (C-1). HRMS (ESI): m/z 310.1278
2
+
(
M +NH ), calcd for C H NO : 310.1285.
4
15 20
6
4
.1.5.3. 3,6-Anhydro-2-deoxy-5,7-O-methylidene-7-C-phenyl-L-glycero-D-ido-heptono-1,4-
lactone (4b)
Yield: 82% (Procedure A); 95% (Procedure B). Colourless needles, mp 195 °C (CH Cl /hexane),
2
2
2
D
0
[
(
α] +72.0 (c 0.1, CHCl ); R =0.3 (1:2 light petroleum/Et O). IR (film): ν 1789 (C=O), 1497
3 f 2 max
1
Ph). H NMR (CDCl ): δ 2.60 (dd, 1 H, J2a,2b=18.8, J2a,3=1.1 Hz, H-2a), 2.18 (dd, 1 H, J2a,2b=18.9,
3
J2b,3=5.6 Hz, H-2b), 4.18 (t, 1 H, J =J =1.9 Hz, H-6), 4.55 (br s, 1 H, H-5), 4.89 (d, 1 H, J =1.7
5,6
6,7
6,7
Hz, H-7), 4.93 (d, 1 H, Jgem=6.6 Hz, CH -a), 4.95 (d, 1 H, J =4.7 Hz, H-4), 5.19 (m, 1 H, H-3),
2
3,4
5
.24 (d, 1 H, Jgem=6.5 Hz, CH -b), 7.48–7.29 (m, 5 H, Ph). NOE contact: H-4 and H-5; NOE
2
1
3
contact: H-7 and H-6. C NMR (CDCl ): δ 35.7 (C-2), 75.6 (C-6), 77.2 (C-7), 77.6 (C-3), 77.7 (C-
3
5
2
), 85.3 (C-4), 92.2 (CH ), 126.0, 128.0, 128.3 and 137.1 (Ph), 175.2 (C-1). HRMS (ESI): m/z
2
+
80.1175 (M +NH ), calcd for C H NO : 280.1180.
4
14 18
5
4
.1.6. General procedure for the preparation of cyclic carbonates 4c and 3d
To a solution of 1 or 2 (1 equiv) in dry CH CN (0.03 M) was added 1,1′-carbonyldiimidazole (2
3
equiv) and the mixture was stirred at 46–48 °C (1.5 h for 1, 2 h for 2). After the mixture cooled to
1
3

ACCEPTED MANUSCRIPT
room temperature it was concentrated and the residue purified by flash chromatography (24:1
†
CH Cl /Me CO for 3d, 24:1 CH Cl /Me CO for 4c).
2
2
2
2
2
2
4
.1.6.1. 3,6-Anhydro-2-deoxy-5,7-O-carbonyl-7-C-phenyl-
D-glycero-D-ido-heptono-1,4-lactone
(
3d)
20
Yield 96%. Colourless needles, mp 165 °C (CH Cl /hexane), [α] +159.0 (c 0.1, CH Cl ); R =0.48
2
2
D
2
2
f
(24:1 CH Cl /Me CO). IR (KBr): ν 1815 (C=O, cyclic carbonate), 1759 (C=O, lactone), 1499
2 2 2 max
1
(
Ph). H NMR (CDCl ): δ 2.78 (d, 1 H, J2a,2b=18.7 Hz, H-2a), 2.89 (dd, 1 H, J2a,2b=18.9, J2a,3=6.4
3
Hz, H-2b), 4.50 (t, 1 H, J =J =2.9 Hz, H-6), 4.97 (d, 1 H, J =2.9 Hz, H-5), 5.11 (d, 1 H, J =4.3
5
,6
6,7
5,6
3,4
1
3
Hz, H-4), 5.18 (m, 1 H, H-3), 5.70 (d, 1 H, J =2.3 Hz, H-7), 7.23–7.58 (m, 5 H, Ph). C NMR
6
,7
(
CDCl ): δ 35.5 (C-2), 75.2 (C-6), 77.9 (C-3), 79.6 (C-5), 79.7 (C-7), 84.8 (C-4), 124.9, 129.4,
3
134.5, 135.2 (Ph), 146.9 (C=O, cyclic carbonate), 173.6 (C-1). HRMS (ESI): m/z 294.0971
+
(
M +NH ), calcd for C H NO : 294.0972.
4
14 16
6
4
.1.6.2. 3,6-Anhydro-2-deoxy-5,7-O-carbonyl-7-C-phenyl-L-glycero-D-ido-heptono-1,4-lactone
(
4c)
20
Yield 73%. Colourless needles, mp 223 °C (CH Cl /CHCl ), [α] +85.0 (c 0.1, CH Cl ); R =0.32
2
2
3
D
2
2
f
(24:1 CH Cl /Me CO). IR (KBr): ν 1794 (C=O, cyclic carbonate), 1732 (C=O, lactone), 1502
2 2 2 max
1
(
Ph). H NMR (DMSO-d ): δ 2.52 (d, 1 H, J2a,2b=18.7 Hz, H-2a), 2.92 (dd, 1 H, J2a,2b=18.9,
6
J2a,3=6.6 Hz, H-2b), 4.77 (br s, 1 H, H-6), 5.01 (m, 1 H, H-3), 5.17 (d, 1 H, J =4.5 Hz, H-4), 5.37
3,4
1
3
(
d, 1 H, J =3.1 Hz, H-5), 5.90 (br s, 1H, H-7) and 7.30–7.56 (m, 5 H, Ph). C NMR (DMSO-d ): δ
4
,
5
6
35.3 (C-2), 72.8 (C-6), 77.2 (C-7), 78.0 (C-3), 81.8 (C-5), 84.7 (C-4), 126.7, 128.5, 128.7, 135.2
+
(
Ph), 146.9 (C=O, cyclic carbonate), 175.1 (C-1). HRMS (ESI): m/z 294.0970 (M +NH ), calcd for
4
C H NO : 294.0972.
14
16
5
4
.1.7. (7S)-3,6-anhydro-2-deoxy-7-C-hydroxy-5,7-O-methylene-
D-ido-heptono-1,4-lactone (12)
A solution of 11 [29] (0.33 g, 1.62 mmol) and H IO (0.331 g, 1.45 mmol) in dry CH CN (30 mL)
5
6
3
was stirred at room temperature for 20 h. The mixture was evaporated, and the residue purified by
flash column chromatography (9:1 CH Cl /Me CO). Pure 12 (0.26 g, 80%) was isolated as a white
2
2
2
2
0
glassy solid. Recrystallization from Me CO/hexane gave cloudy needles, mp 152–153 °C, [α]
2
D
1
+
130.0 (c 0.25, Me CO); R =0.31 (9:1 CH Cl /Me CO). IR (KBr): ν 3338 (OH), 1763 (C=O). H
2 f 2 2 2 max
†
Anhydrous solvents must be used as eluents for flash column chromatography. Otherwise, it may cause a significant
drop in yield.
1
4

ACCEPTED MANUSCRIPT
NMR (CDCl ): δ 2.53 (dd, 1 H, J2a,2b=18.7, J2a,3=1.4 Hz, H-2a), 2.92 (dd, 1 H, J2a,2b=18.7, J2b,3=6.1
3
Hz, H-2b), 3.71 (d, 1 H, J =2.7 Hz, H-6), 4.48 (br s, 1 H, H-5), 4.61 (d, 1 H, J =6.3 Hz, CH -a),
5
,6
gem
2
4
.92 (d, 1 H, J =4.1 Hz, H-4), 5.02 (m, 1 H, H-3), 5.15–5.25 (m, 2 H, H-7 and CH -b), 5.95 (d, 1
3
,
4
2
1
3
H, J7,OH=4.3 Hz, OH). C NMR (CDCl ): δ 36.1 (C-2), 75.9 (C-5), 76.1 (C-6), 78.5 (C-3), 83.6
3
+
(
CH ), 86.3 (C-4), 90.2 (C-7), 175.8 (C-1). HRMS (ESI): m/z 220.0816 (M +NH ), calcd for
2
4
C H NO : 220.0816.
8
14
6
4
.1.8. (7S)- (5a) and (7R)-3,6-anhydro-2-deoxy-7-C-cinnamoyloxy-5,7-O-methylene-
D-ido-heptono-
1,4-lactone (6a)
To a cooled (0 °C) and stirred solution of 12 (0.12 g, 0.59 mmol) and trans-cinnamoyl chloride
0.148 g, 0.89 mmol) in dry CH CN (5 mL) was added DMAP (0.145 g, 1.19 mmol). The mixture
(
3
was stirred at 0 °C for 0.5 h and then at room temperature for 2 h. The mixture was poured into 5%
aq NaCl (100 mL) and extracted with CH Cl (2×30 mL) and EtOAc (30 mL). The combined
2
2
organic solutions were dried and evaporated and the residue was purified by flash column
chromatography (9:1 toluene/EtOAc). Eluted first was pure 5a (0.12 g, 61%) isolated as a
colourless solid. Recrystallization from CH Cl /hexane gave colourless needles, mp 180 °C, [α]
2
D
0
2
2
+
205.8 (c 0.5, CHCl ); R =0.33 (4:1 toluene/EtOAc). IR (film): ν 1793 (C=O, lactone), 1724
3
f
max
1
(
C=O, cinnamate), 1636 (C=C, cinnamate), 1578 and 1497 (Ph). H NMR (CDCl ): δ 2.70 (br d, 1
3
H, J2a,2b=18.2 Hz, H-2a), 2.82 (dd, 1 H, J2a,2b=18.9, J2b,3=5.4 Hz, H-2b), 3.90 (br s, 1 H, H-6), 4.65
(
br s, 1 H, H-5), 4.82 (d, 1 H, Jgem=6.5 Hz, CH -a), 4.96 (d, 1 H, J =4.2 Hz, H-4), 5.12 (m, 2 H, H-
2 3,4
3
and CH ), 5.29 (s, 2 H, CH Cl ), 6.32 (s, 1 H, H-7), 6.46 (d, 1 H, J2′,3′=16.1 Hz, H-2′), 7.33–7.61
2 2 2
1
3
(
m, 5 H, Ph), 7.77 (d, 1 H, J2′,3′=16.1 Hz, H-3′). C NMR (CDCl ): δ 35.6 (C-2), 53.5 (CH Cl ),
3 2 2
7
1
3.5 (C-6), 75.5 (C-5), 77.8 (C-3), 85.2 (CH ), 85.4 (C-4), 88.2 (C-7), 116.5 (C-2′), 128.3, 129.0,
2
30.9, 133.8 (Ph), 147.0 (C-3′), 164.4 (C=O, cinnamate), 174.6 (C-1). HRMS (ESI): m/z 371.0545
+
(
M +K), calcd for C H KO : 371.0528.
1
7
16
7
Eluted second was pure 6a (0.05 g, 25%). Recrystallization from CH Cl /hexane gave colourless
2
2
20
powder, mp 176–177 °C, [α] +6.8 (c 0.25, Me CO); R =0.27 (4:1 toluene/EtOAc). IR (KBr): ν
max
D
2
f
1
1
793 (C=O, lactone), 1732 (C=O, cinnamate), 1636 (C=C, cinnamate), 1578 and 1497 (Ph). H
NMR (CDCl ): δ 2.81 (d, 2 H, J =3.4 Hz, H-2), 4.18 (t, 1 H, J =J =1.8 Hz, H-6), 4.61 (br s, 1 H,
3
2,3
5,6
6,7
H-5), 4.91–4.98 (m, 2 H, H-4 and CH ), 5.12 (d, 1 H, J =6.9 Hz, CH ), 5.20 (m, 1 H, H-3), 6.15
2
gem
2
(d, 1 H, J =1.6 Hz, H-7), 6.54 (d, 1 H, J2′,3′=16.0 Hz, H-2′),7.59–7.32 (m, 5 H, J=8.8 Hz, Ph), 7.82
6,7
1
3
(
d, 1 H, J2′,3′=16.1 Hz, H-3′). C NMR (CDCl ): δ 35.6 (C-2), 73.9 (C-6), 78.3 (C-5), 78.6 (C-3),
3
1
5

ACCEPTED MANUSCRIPT
8
1
4.7 (C-4), 90.2 (CH ), 90.6 (C-7), 116.2 (C-2′), 128.3, 128.9, 130.9, 133.8 (Ph), 147.5 (C-3′),
2
+
64.6 (C-1′), 174.6 (C-1). HRMS (ESI): m/z 350.1236 (M +NH ), calcd for C H NO : 350.1234.
4
17 20
7
4
.1.9. (7S)- (5b) and (7R)-3,6-anhydro-2-deoxy-7-C-(trans-4-fluorocinnamoyloxy)-5,7-O-
-ido-heptono-1,4-lactone (6b)
methylene-
D
Procedure A. To a stirred solution of 12 (0.065 g, 0.32 mmol) in dry CH Cl (7 mL) were added
2
2
successively trans-4-fluorocinnamic acid (0.123 g, 0.74 mmol), DCC (0.161 g, 0.78 mmol) and
DMAP (0.181 g, 1.48 mmol). The mixture was stirred at room temperature for 24 h, then poured in
water (100 mL) and extracted with CH Cl (3×25 mL). The combined extracts were washed with
2
2
10% aq NaCl (100 mL), dried and evaporated. Flash column chromatography (9:1 toluene/EtOAc)
of the residue afforded pure 5b (0.068 g, 60%) as a colourless glassy solid.
Procedure B. To a cooled (0 °C) and stirred solution of 12 (0.075 g, 0.37 mmol), Ph P (0.214 g,
3
0
4
.82 mmol) and trans-4-fluorocinnamic acid (0.117 g, 0.7 mmol) in dry CH CN (10 mL) was added
3
0% DEAD in toluene (0.32 mL, 0.74 mmol). The mixture was stirred at 0 °C for 0.5 h and then at
room temperature for 1 h. The mixture was concentrated and the residue purified on a column of
flash silica (22:3 toluene/EtOAc). Eluted first was pure 5b (0.026 g, 20%), which crystallized from
20
CH Cl /hexane in the form of colourless needles, mp 190–191 °C, [α] +221.4 (c 0.5, Me CO);
2
2
D
2
R =0.37 (4:1 toluene/EtOAc). IR (KBr): ν 1789 (C=O, lactone), 1725 (C=O, cinnamate), 1638
f
max
1
(
C=C, cinnamate), 1600 (Ph). H NMR (CDCl ): δ 2.71 (br d, 1 H, J2a,2b=18.6 Hz, H-2a), 2.82 (dd,
3
1
H, J2a,2b=18.9, J2b,3=5.4 Hz, H-2b), 3.89 (br s, 1 H, H-6), 4.65 (br s, 1 H, H-5), 4.83 (d, 1 H,
Jgem=6.5 Hz, CH -a), 4.97 (d, 1 H, J =4.2 Hz, H-4), 5.07–5.17 (m, 2 H, H-3 and CH -b), 6.31 (s, 1
2
3,4
2
H, H-7), 6.39 (d, 1 H, J2′,3′=16.0 Hz, H-2′), 7.11 and 7.55 (2×m, 4 H, Ph), 7.73 (d, 1 H, J2′,3′=16.0
1
3
Hz, H-3′). C NMR (CDCl ): δ 35.6 (C-2), 73.5 (C-6), 75.5 (C-5), 77.7 (C-3), 85.1 (CH ), 85.4 (C-
3
2
4
3
3
), 88.3 (C-7), 116.4 (C-2′), 116.0, 116.2, 116.4, 130.1, 130.2, 130.3, 162.2, 166.2 (Ph), 145.6 (C-
+
′), 164.7 (C-1′), 174.6 (C-1). HRMS (ESI): m/z 368.1147 (M +NH ), calcd for C H FNO :
4
17 19
7
68.1140. Eluted second was pure 6b (0.059 g, 45%). Crystallization from CH Cl /hexane gave
2
2
20
colourless powder, mp 194–195 °C, [α] +10.4 (c 0.25, Me CO); R =0.30 (4:1 toluene/EtOAc). IR
D
2
f
1
(
KBr): νmax 1792 (C=O, lactone), 1732 (C=O, cinnamate), 1637 (C=C, cinnamate), 1600 (Ph). H
NMR (CDCl ): δ 2.81 (d, 2 H, J =3.3 Hz, H-2), 4.17 (br s, 1 H, H-6), 4.61 (br s, 1 H, H-5), 4.89–
3
2,3
5
.00 (m, 2 H, H-4 and CH -a), 5.12 (d, 1 H, J =6.8 Hz, CH -b), 5.20 (m, 1 H, H-3), 6.14 (d, 1 H,
2 gem 2
J =1.4 Hz, H-7), 6.45 (d, 1 H, J2′,3′=16.0 Hz, H-2′), 7.09 and 7.53 (2×m, 4 H, Ph), 7.78 (d, 1 H,
6
,7
1
3
J2′,3′=16.0 Hz, H-3′). NOE contact: H-5 and H-7. C NMR (CDCl ): δ 35.6 (C-2), 73.9 (C-6), 78.5
3
(
C-5), 78.6 (C-3), 84.7 (C-4), 90.2 (CH ), 90.6 (C-7), 116.3 (C-2′), 115.88, 115.91, 116.0, 130.0,
2
1
6

ACCEPTED MANUSCRIPT
1
3
30.1, 130.2, 130.4, 162.2, 166.2 (Ph), 146.1 (C-3′), 164.5 (C-1′), 174.6 (C-1). HRMS (ESI): m/z
+
68.1133 (M +NH ), calcd for C H FNO : 368.1140.
4
17 19
7
4
.1.10. (7S)- (5c) and (7R)-3,6-anhydro-2-deoxy-7-C-(trans-4-nitrocinnamoyloxy)-5,7-O-
-ido-heptono-1,4-lactone (6c)
methylene-
D
To a cooled (0 °C) and stirred solution of 12 (0.115 g, 0.57 mmol) and trans-4-nitrocinnamoyl
chloride (0.157 g, 0.74 mmol) in dry CH CN (5 mL) was added DMAP (0.108 g, 0.88 mmol). The
3
mixture was stirred at 0 °C for 0.5 h and then at room temperature for 1.5 h. A new portion of trans-
4-nitrocinnamoyl chloride (0.157 g, 0.74 mmol) and DMAP (0.108 g, 0.88 mmol) was added and
stirring at room temperature was continued for additional 1 h. The mixture was poured into 5% aq
NaCl (100 mL) and extracted with EtOAc (3×30 mL). The combined organic solutions were dried
and evaporated and the residue purified by flash column chromatography (49:1 CH Cl /Me CO).
2
2
2
Eluted first was pure 5c (0.136 g, 63%). Recrystallization from CH Cl /hexane gave white flakes,
2
2
20
mp 198–200 °C, [α] +225.8 (c 0.5, Me CO); R =0.32 (4:1 toluene/EtOAc). IR (KBr): ν 1780
D
2
f
max
1
(
(
(
C=O, lactone), 1717 (C=O, cinnamate), 1633 (C=C, cinnamate), 1604 (Ph), 1514 (NO ). H NMR
2
CDCl ): δ 2.72 (d, 1 H, J2a,2b=17.8 Hz, H-2a), 2.84 (dd, 1 H, J2a,2b=17.9, J2b,3=5.4 Hz, H-2b), 3.90
3
br s, 1 H, H-6), 4.66 (br s, 1 H, H-5), 4.85 (d, 1 H, Jgem=6.5 Hz, CH -a), 4.98 (d, 1 H, J =4.1 Hz,
2
3,4
H-4), 5.11 (d, 1 H, Jgem=6.6 Hz, CH -b), 5.15 (m, 1 H, H-3), 6.33 (s, 1 H, H-7), 6.59 (d, 1 H,
2
1
3
J2′,3′=16.0 Hz, H-2′), 7.72 and 8.27 (2×d, 4 H, J=8.8 Hz, Ph), 7.79 (d, 1 H, J2′,3′=16.1 Hz, H-3′). C
NMR (CDCl ): δ 35.6 (C-2), 73.4 (C-6), 75.5 (C-5), 77.8 (C-3), 85.2 (CH ), 85.4 (C-4), 88.7 (C-7),
3
2
120.8 (C-2′), 124.2, 128.9, 139.8, 148.8 (Ph), 143.9 (C-3′), 163.5 (C-1′), 174.6 (C-1). HRMS (ESI):
+
m/z 395.1085 (M +NH ), calcd for C H N O : 395.1085. Eluted second was the minor
4
17 19
2
9
stereoisomer 6c (0.07 g, 33%). Recrystallization from CH Cl /hexane gave colourless powder, mp
2
2
2
0
2
32–233 °C, [α] −1.6 (c 0.5, Me CO); R =0.22 (4:1 toluene/EtOAc). IR (KBr): ν 1794 (C=O,
D
2
f
max
1
lactone), 1745 (C=O, cinnamate), 1640 (C=C, cinnamate), 1522 (NO ), 1603 (Ph). H NMR
2
(
CDCl ): δ 2.82 (d, 2 H, J =4.4 Hz, H-2), 4.18 (t, 1 H, J =J =1.9 Hz, H-6), 4.63 (br s, 1 H, H-5),
3 2,3 5,6 6,7
4
.94 (d, 1 H, Jgem=6.9 Hz, CH -a), 4.97 (dd, 1 H, J =4.3, J =0.6 Hz, H-4), 5.13 (d, H, Jgem=6.9
2 3,4 4,5
Hz, CH -b), 5.21 (m, 1 H, H-3), 6.15 (d, 1 H, J =1.7 Hz, H-7), 6.65 (d, 1 H, J2′,3′=16.0 Hz, H-2′),
2
6,7
7.70 and 8.261 (2×d, 4 H, J=8.8 Hz, Ph), 7.84 (d, 1 H, J2′,3′=16.1 Hz, H-3′). NOE contact: H-5 and
1
3
H-7. C NMR (CDCl ): δ 35.6 (C-2), 73.8 (C-6), 78.4 (C-5), 78.6 (C-3), 84.7 (C-4), 90.3 (CH ),
3
2
91.0 (C-7), 120.6 (C-2′), 124.2, 128.9, 139.8 (Ph), 144.3 (C-3′), 163.7 (C-1′), 174.5 (C-1). HRMS
+
(
ESI): m/z 400.0639 (M +Na), calcd for C H NNaO : 400.0639.
1
7
15
9
4
.1.11. (7S)- (5d) and (7R)-3,6-anhydro-2-deoxy-7-C-(trans-4-methoxycinnamoyloxy)-5,7-O-
1
7

ACCEPTED MANUSCRIPT
methylene-
D-ido-heptono-1,4-lactone (6d)
Procedure A. To a stirred solution of 12 (0.125 g, 0.62 mmol) in dry CH Cl (15 mL) were added
2
2
successively trans-4-methoxycinnamic acid (0.23 g, 1.29 mmol), DCC (0.323 g, 1.57 mmol) and
DMAP (0.32 g, 2.61 mmol). The mixture was stirred at room temperature for 20 h, then suspended
in water (100 mL) and extracted with CH Cl (3×30 mL). The combined organic solutions were
2
2
washed with 10% aq NaCl (100 mL), dried and evaporated. Flash column chromatography (9:1
toluene/EtOAc) of the residue gave pure 5d (0.135 g, 60%) as a colourless solid. Recrystallization
20
from CH Cl /hexane gave colourless needles, mp 182–183 °C, [α] +303.6 (c 0.25, Me CO);
2
2
D
2
R =0.33 (4:1 toluene/EtOAc).
f
Procedure B. To a cooled (0 °C) and stirred solution of 12 (0.08 g, 0.39 mmol), Ph P (0.285 g, 1.09
3
mmol) and trans-4-methoxycinnamic acid (0.167 g, 0.94 mmol) in dry CH CN (12 mL) was added
3
40% DEAD in toluene (0.43 mL, 0.99 mmol). The mixture was stirred at 0 °C for 0.5 h and then at
room temperature for 1 h. The mixture was evaporated and the residue purified by flash column
chromatography (99:1 → 49:1 CH Cl /Me CO). Eluted first was pure 5d (0.015 g, 10%) as a
2
2
2
colourless glassy solid. Recrystallization from CH Cl /hexane gave colourless needles, mp 181–182
2
2
2
0
°
C, [α] +254.4 (c 0.25, Me CO); R =0.33 (4:1 toluene/EtOAc). IR (KBr): ν 1773 (C=O,
2 f max
D
1
lactone), 1710 (C=O, cinnamate), 1633 (C=C, cinnamate), 1604 (Ph). H NMR (CDCl ): δ 2.71 (br
3
d, 1 H, J2a,2b=18.5 Hz, H-2a), 2.82 (dd, 1 H, J2a,2b=18.9, J2b,3=5.4 Hz, H-2b), 3.84 (s, 3 H, CH3),
3
.89 (br s, 1 H, H-6), 4.65 (br s, 1 H, H-5), 4.83 (d, 1 H, Jgem=6.5 Hz, CH -a), 4.96 (d, 1 H, J =4.2
2 3,4
Hz, H-4), 5.07–5.17 (m, 2 H, H-3 and CH -b), 6.31 (s, 1 H, H-7), 6.32 (d, 1 H, J2′,3′=16.0 Hz, H-2′),
2
1
3
6
5
1
.93 and 7.51 (2×d, 4 H, Ph), 7.73 (d, 1 H, J2′,3′=15.9 Hz, H-3′). C NMR (CDCl ): δ 35.6 (C-2),
3
5.4 (OCH ), 73.6 (C-6), 75.5 (C-5), 77.7 (C-3), 85.1 (CH ), 85.4 (C-4), 88.1 (C-7), 113.8 (C-2′),
3
2
14.4, 126.6, 130.1, 161.9 (Ph), 146.7 (C-3′), 164.7 (C-1′), 174.6 (C-1). HRMS (ESI): m/z 380.1339
+
(
M +NH ), calcd for C H NO : 380.1340. Eluted second was pure 6d (0.05 g, 35%).
4
18 22
8
20
Recrystallization from CH Cl /hexane gave pure 6d as colourless needles, mp 184 °C, [α] −0.8 (c
2
2
D
0
.25, Me CO); R =0.23 (4:1 toluene/EtOAc). IR (KBr): ν 1788 (C=O, lactone), 1731 (C=O,
2 f max
1
cinnamate), 1632 (C=C, cinnamate), 1602 (Ph). H NMR (CDCl ): δ 2.82 (d, 2 H, J =3.4 Hz, H-
3
2,3
2
), 3.84 (s, 3 H, OCH ), 4.17 (t, 1 H, J =J =1.8 Hz, H-6), 4.60 (br s, 1 H, H-5), 4.93 (d, 1 H,
3 5,6 6,7
Jgem=6.9 Hz, CH -a), 4.95 (br d, 1 H, J =4.4 Hz, H-4), 5.11 (d, 1 H, J =6.9 Hz, CH -b), 5.20 (m,
2
3,4
gem
2
1
H, H-3), 6.14 (d, 1 H, J =1.6 Hz, H-7), 6.65 (d, 1 H, J2′,3′=15.9 Hz, H-2′), 6.91 and 7.50 (2×d, 4
6,7
1
3
H, J=8.7 Hz, Ph), 7.78 (d, 1 H, J2′,3′=15.9 Hz, H-3′). NOE contact: H-5 and H-7. C NMR (CDCl ):
3
δ 35.6 (C-2), 55.4 (OCH ), 74.0 (C-6), 78.3 (C-5), 78.5 (C-3), 84.7 (C-4), 90.2 (CH ), 90.5 (C-7),
3
2
1
8

ACCEPTED MANUSCRIPT
113.8 (C-2′), 114.4, 126.6, 130.1, 161.8 (Ph), 147.2 (C-3′), 165.0 (C-1′), 174.6 (C-1). HRMS (ESI):
+
m/z 380.1339 (M +NH ), calcd for C H NO : 380.1340.
4
18 22
8
4.2. MTT assay
The colorimetric MTT assay was carried out following the procedure recently reported by us [34].
Acknowledgement
Financial support from the Ministry of Education, Science and Technological Development of the
Republic of Serbia (Grant No 172006) is gratefully acknowledged.
Appendix A. Supplementary material
CCDC 979783 contains the supplementary crystallographic data for structure 3a. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: +44 1223 336 033).
Appendix B. Supplementary data
These data include modified experimental procedures for preparation of starting compounds (7 and
1
13
8
), and copies of H, and C NMR spectra of the most important compounds described in this
article. Additional crystallographic results are also included in this section. Supplementary data
associated with this article can be found in online version.
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1
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(
2
0

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[
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1
2
2

ACCEPTED MANUSCRIPT
Captions
Figure 1. ORTEP presentation of compound 3a.
Scheme 1. Design of conformationally constrained (+)-goniofufurone and 7-epi-(+)-goniofufurone
mimics 3 and 4, as well as the corresponding cinnamic isosteres 5 and 6, respectively.
Scheme 2. Reagents and conditions: (a) BnBr, NaH, DMF, 0 ºC for 0.5 h, then rt for 1.5 h; (b) 50%
aq TFA, rt, 18 h; (c) Meldrum’s acid, Et N, DMF, 44–46 ºC, 66 h; (d) H -Pd/C, MeOH, rt, 48 h,
3
2
3
9% from 7, 48% from 8; (e) H IO , PCC (cat), MeCN, 0 ºC, 2 h, 96%; (f) NaBH , L-tartaric acid,
5
6
4
THF, reflux for 2 h, then cooled to −18 ºC added 10 and stirred for 20 h, 81% of 1, 17% of 2.
Scheme 3. Reagents and conditions: (a) Me C(OMe) , TsOH, Me CO, rt, 3.5 h for 1, 4.5 h for 2,
2
2
2
95% of 3a, 95% of 4a; (b) paraformaldehyde, TsOH, MeCN, rt, 20 h for 1, 48% of 3b, 49% of 3c,
7
2 h for 2, 82% of 4b; (c) SOCl , DMSO, 65 ºC, 1.5 h, 38% of 3b, 51% of 3c, 95% of 4b; (d)
2
Imd CO, MeCN, 46–48 ºC, 1.5 h for 1, 96% of 3d, 2 h for 2, 73% of 4c.
2
Scheme 4. Reagents and conditions: (a) see references [27] and [28]; (b) H IO , MeCN, rt, 20 h,
5
6
80%.
2
3

ACCEPTED MANUSCRIPT
Table 1. Preparation of (+)-goniofufurone and 7-epi-(+)-goniofufurone mimics 5a–d and 6a–d,
respectively
Cinnamic acid
derivative
Major product
(isolated yield, %)
Minor product
(isolated yield, %)
Entry
Reagents and conditions
DMAP, MeCN, 0 °C for
1
2
3
4
5
6
R = H, X = Cl
R = F, X = OH
R = F, X = OH
5a R = H (61)
5b R = F (60)
6b R = F (45)
6a R = H (25)
—
0
.5 h, then rt for 2 h
DCC, DMAP, CH Cl , rt
2
2
for 24 h
Ph P, DEAD, MeCN, 0 °C
3
5b R = F (20)
for 0.5 h, then rt for 1 h
DMAP, MeCN, 0 °C for
R = NO , X = Cl
5c R = NO (63)
6c R = NO (33)
2
2
2
0
.5 h, then rt for 2.5 h
DCC, DMAP, CH Cl , rt
2
2
R = OMe, X = OH
R = OMe, X = OH
5d R = OMe (60)
6d R = OMe (35)
—
for 20 h
Ph P, DEAD, MeCN, 0 °C
3
5d R = OMe (10)
for 0.5 h, then rt for 1 h
2
4

ACCEPTED MANUSCRIPT
Table 2. In vitro cytotoxicity of (+)-goniofufurone (1), 7-epi-(+)-goniofufurone (2), the corresponding
mimics 3a–d, 4a–c, 5a–d, 6a–d and DOX
a
IC50 (µM)
Compounds
K562
0.41
HL-60
>100
2.36
Jurkat
32.45
34.15
18.21
13.64
11.52
5.06
Raji
MCF-7
16.59
87.45
23.45
27.79
1.01
MDA-MB 231 HeLa
Hs 294T
>100
>100
35.64
45.32
>100
>100
0.002
>100
89.74
43.58
>100
>100
>100
2.53
MRC-5
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
0.10
1
3
3
3
3
5
5
5
5
2
4
4
4
6
6
6
6
18.45
3.25
75.34
5.27
8.32
a
b
c
16.59
>100
>100
5.59
1.64
10.08
14.34
33.78
8.08
17.89
12.45
25.31
1.01
>100
>100
2.37
18.87
12.36
14.26
0.001
0.02
d
a
b
c
3.16
27.32
>100
3.64
4.08
>100
>100
8.77
2.36
>100
>100
0.042
18.64
22.51
3.33
5.78
>100
1.01
6.37
20.01
4.32
8.79
d
1.24
>100
9.24
>100
58.7
12.51
0.89
0.028
0.17
22.02
1.25
1.25
a
b
c
1.01
1.06
24.89
>100
>100
2.36
9.75
0.023
4.46
0.24
1.01
8.08
3.02
12.85
8.45
7.89
15.78
7.56
32.45
>100
32.22
>100
51.79
0.20
5.67
a
b
c
>100
4.32
>100
15.47
>100
12.01
0.03
0.23
12.07
35.38
25.61
0.92
87.23
1.32
5.69
11.69
1.01
>100
>100
>100
4.50
>100
3.68
>100
3.03
d
69.24
2.98
2.21
DOX
0.25
0.09
0.065
a
IC50 is the concentration of compound required to inhibit the cell growth by 50% compared to an untreated control. Values are means of three
independent experiments. Coefficients of variation were less than 10%.
2
5

ACCEPTED MANUSCRIPT
Figure 1.
2
6

ACCEPTED MANUSCRIPT
Scheme 1.
2
7

ACCEPTED MANUSCRIPT
Scheme 2.
2
8