A step-wise synthetic approach is necessary to access γ-conjugates of folate: Folate-conjugated prodigiosenes

Article abstract of DOI:10.1039/c9ra01435g

Despite the vast literature that describes reacting folic acid with a pharmacophore, this route is ineffective in providing the correct regioisomer of the resulting conjugate. We herein present a step-wise route to the preparation of nine folate conjugate

Full text of DOI:10.1039/c9ra01435g

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A step-wise synthetic approach is necessary to
access g-conjugates of folate: folate-conjugated
prodigiosenes†
Cite this: RSC Adv., 2019, 9, 14078
*
Carlotta Figliola,‡ Estelle Marchal,‡ Brandon R. Groves and Alison Thompson
Despite the vast literature that describes reacting folic acid with a pharmacophore, this route is ineffective in
providing the correct regioisomer of the resulting conjugate. We herein present a step-wise route to the
preparation of nine folate conjugates of the tripyrrolic prodigiosene skeleton. The strict requirement for
step-wise construction of the folate core is demonstrated, so as to achieve conjugation at only the
desired g-carboxylic acid and thus maintain the a-carboxylic site for folate receptor (FRa) recognition.
Linkages via ethylenediamine, polyethylene glycol and glutathione are demonstrated.
Received 25th February 2019
Accepted 23rd April 2019
DOI: 10.1039/c9ra01435g
rsc.li/rsc-advances
by FRa.33–35 Consequently, cognisant that folate-conjugated
drugs do not generally enter normal cells,36 folic acid has
Introduction
been employed in the synthesis of multiple drug-delivery
systems for chemotherapeutic treatment and imaging.
Given the potency of prodigiosenes and the targeting ability
of folate, we herein report the synthesis of the rst series of
folate–prodigiosene conjugates. In doing so, we emphasize the
ineffectiveness of the much-utilised direct synthetic approach
to couple unmodied folic acid with the desired pharmaco-
phore. Our observations and comments contrast with the vast
literature that apparently describes the folate-targeted bioac-
tivity of unpuried and uncharacterised material that results
from such direct coupling. We categorically demonstrate that
this direct approach, despite its wide use by others, gives rise to
mixtures that include both regioisomers featuring the phar-
macophore coupled to both carboxyl sites of folic acid. Instead,
we demonstrate the requirement for step-wise construction of
the folate core, so as to achieve conjugation at only the desired
g-carboxylic acid and thus maintenance of the a-carboxylic site
for FRa recognition.37
Prodigiosin is a tripyrrolic, red pigmented natural product,
produced by Gram positive and Gram negative bacteria,
including certain strains of Serratia marcescens (Fig. 1).1,2 Pro-
digiosin is well known to exhibit immunosuppressive, antimi-
crobial and anticancer properties, yet modern uses extend from
sunscreen3 to antibacterial dyes for silk4 and cotton.5 Known
mechanisms of bioactivity include H+/Clꢀ exchange, oxidative
DNA cleavage through Cu(II) chelation and signal-transduction
interference.6–15 Synthetic mimics of prodigiosin, named pro-
digiosenes,16 with modications on the A-, B- or C-ring17–24 have
been shown to maintain the biological activity of the parent
compound yet with 100-fold improvements in selectivity
towards malignant cells and with 100-fold reduction of systemic
toxicity in mice compared to the natural product (R ¼ CO2iPr, R1
¼ Me, Fig. 1).25 Furthermore, the study of these synthetic
analogues has enriched the knowledge of structure–activity
relationships (SAR) for a better understanding of the biological
activity of prodigiosin.
Folic acid (vitamin B9, Fig. 2) is considered26 a promising
biomarker for triple-negative breast cancer (TNBC).27 More than
50% of TNBCs overexpress folate receptor alpha (FRa), as do
a limited number of other cancers28 (e.g. ovarian cancers)29,30
along with those tissues where TNBC is likely to result in
metastasis, such as brain and lung.31 Importantly, FRa is
present on only a few types of healthy cells (activated macro-
phages and proximal tubules of kidneys),32 and, crucially, the
uptake of the vitamin folic acid (as a folate salt) is not mediated
Results and discussion
Our folate–prodigiosene conjugates (Fig. 3) feature prodigio-
sene 1 as the pharmacophore,38 with varied aliphatic spacer
length (n ¼ 2, 4, 8) leading to the folate moiety. The conjugated
carbonyl group on the b-position of the C-ring has been shown
to facilitate purication of prodigiosene intermediates21 and so
it, and the adjacent b-methyl substituent, were incorporated
into the synthetic strategy. Linkers were chosen to increase
either the lipophilicity39 (ethylenediamine, DA) or the water-
solubility and biocompatibility40,41 (polyethylene glycol, PEG)
of the conjugates, or to enable intracellular redox-mediated
cleavage by glutathione (disulde, SS, Fig. 3).42–44
Department of Chemistry, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2,
Canada. E-mail: Alison.Thompson@dal.ca; Tel: +1-902-494-3305
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra01435g
‡ Equal contributions.
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Fig. 1 Naturally occurring prodigiosin, and SAR of prodigiosene analogues.17–25
was found to be highly sensitive to basic work-up conditions
and purication using ash chromatography, both of which
caused cleavage of the disulde.
g-Coupling to folic acid and synthesis of folate–prodigiosene
conjugates
Folic acid formally consists of pteroic acid linked to L-glutamic
acid through a peptide bond (Fig. 2).46 The crystal structure of
human FRa complexed with folic acid reveals a deep binding
pocket with the pteroate element of folate buried inside the
receptor.47 In contrast, the glutamate moiety of folate sits at the
pocket entrance. The a-carboxylic acid of the amino-acid is
involved in the interaction with the FRa and, thus, in the
metabolism and function of folate.37 However, conjugates
bound at the pendant g-carboxylic acid, further away from the
binding pocket, readily undergo binding to FRa. As such, in
order to leave the a-position unmodied, conjugation of phar-
macophores to folic acid must be specic to the g-carboxylic
acid in order to maintain ligand binding affinity.37
Fig. 2 Folic acid, or vitamin B9.
Synthesis of linker-prodigiosene conjugates
In order to synthesise the linker-prodigiosene conjugates 2–4a–
c, prodigiosenes 1a–c were coupled38 to the Boc-protected
linkers 5–7 using HBTU in the presence of DMAP.39,40,45
Compounds 8–10 were thus obtained in moderate-to-excellent
yields (Scheme 1, General procedure in experimental section).
Deprotection, using HCl, afforded the targeted linker-
prodigiosene adducts 2–4 aer basic work-up to liberate the
respective free-bases. However, prodigiosene-linker conjugates
4b$HCl and 4c$HCl were used as crude salts, as the S–S bond
As shown in Fig. 4, three retrosynthetic strategies can be
envisaged to achieve the desired folate–prodigiosene conjugates
(top). The simplest method, Strategy A, involves the direct
Fig. 3 Approach to targeted folate–prodigiosene conjugates.
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Scheme 1 Synthesis of linker-prodigiosene adducts 2–4.
coupling of folic acid with the pharmacophore. Following this synthetic sequences and tedious purication processes and
approach, many literature reports appear to describe the direct have not enjoyed widespread adoption. Indeed, the vast
activation of folic acid, followed by addition of the desired majority of published routes involving folate conjugates steer
amine to afford conjugated folates.48–61 However, we met away from these step-wise approaches.68
Strategy A with considerable scepticism as the presence of two
Given the evident popularity of the direct approach offered
carboxylic acid moieties within folic acid renders two regioiso- by Strategy A, we wanted to unequivocally assess the regiose-
meric coupling products clearly tangible. Given the nature of lective outcome of reacting folic acid with a coupling agent and
those two carboxylic acid groups, we were unable to nd any an alcohol. We thus treated folic acid with DCC and NHS, and
rationale by which to convince ourselves that direct reaction analysed the crude product mixture. Based on the phenyl group
would result in production of the required g-conjugate. signals in the 1H NMR spectrum (see ESI†), the crude NHS-
Furthermore, as conjugates to folic acid are oen soluble only adduct was determined to contain a- and g-adducts in an
in DMSO the separation of the two regioisomers represents approx. 25 : 75 a : g ratio. A solution of the adduct mixture in
a considerable challenge. Adding to our skepticism, we found DMSO was treated with the linker-prodigiosene conjugate 2a in
the literature regarding this direct synthetic approach to be an attempt to form the desired amide linkage. Attempts to
incomplete and unreliable, due to either vagueness of puri- isolate pure material (12a) from the precipitate thus formed
cation techniques or lack of characterization such as to give were completely unsuccessful (Scheme 2). Rather, the crude
assurance of purity. Indeed, upon close inspection it appears mixture was poorly soluble and decomposition occurred on
that there are many published reports that simply use the chromatographic media (alumina and silica). Treatment of the
uncharacterised crude precipitate, obtained following the mix- NHS-adduct mixture with 2b and 2c also resulted in bulk
ing of folic acid, coupling agent and pharmacophore, in studies precipitation, and again separation and purication of the
relating to targeting using folate. Cognisant that coupling with highly insoluble material was not possible. Still intrigued by the
DCC etc. involves ureas and other synthetic intermediates, and apparent widespread success of Strategy A, we treated folic acid
that these oen persist in crude product mixtures, we remained with DCC, NHS and a simple amine to thus employ another
unconvinced that Strategy A would be fruitful as we required route by which to gain insight regarding the regioselectivity of
a procedure that gave unequivocal access to the desired g- activation.57 A solution of the 25 : 75 a : g folate–NHS adduct in
conjugate of folic acid bearing prodigiosenes.
DMSO was treated with octyl amine, as a model amine, and the
Retrosynthetic Strategies B and C (Fig. 4) involve the step- resulting precipitate analyzed using 1H NMR spectroscopy. Both
wise construction of suitably protected and activated folic acid a- and g-regioisomers were present, along with the NHS-
from pteroic acid and L-glutamic acid, allowing for the selective activated folic acid, and purication proved unsuccessful
conjugation of pharmacophore at the desired g-carboxyl site. given the lack of solubility of the material. In short, direct
Strategy B requires that the g-activated, a-protected glutamic activation following Strategy A was found to be wholly unsatis-
acid moiety be coupled with the pharmacophore prior to reac- factory in the quest towards isolated and pure g-appended
tion with the pteroate portion of what will become folate.62–64 conjugates of folic acid.
Strategy C requires that the g-activated, a-protected glutamic
With rm evidence that the direct reaction of folic acid with
acid moiety rst be coupled with activated pteroate portion to coupling agent and alcohol/amine does not regioselectively
create g-activated, a-protected folate prior to reaction with the provide the desired g-regioisomer, we turned our attention to
pharmacophore.65 Solid-state resin approaches66,67 recognise strategies that used sequential protection/activation. We rst
the virtues of a step-wise approach yet, compared to the lure of turned to the applicability of retrosynthetic Strategy B, involving
Strategy A, both step-wise strategies obviously demand long step-wise construction of the folate moiety so as to ensure
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Fig. 4 Retrosynthetic approaches for the synthesis of folate–prodigiosene conjugates.
conjugation at the desired g-carboxyl site. As shown in Fig. 4, presence of ZnCl2 at 30 ꢁC.65 Carboxypeptidase G was purchased
the critical step entails coupling of suitably protected (the base from Sigma and used as is (7 mg; 20 units, since 1 unit ¼ 1
portion) and activated (the acid portion) pteroic acid with mmol minꢀ1 at optimal conditions of 30 ꢁC and pH 7.3). The
a derivative of L-glutamic acid that has been pre-linked to the enzyme operates optimally at pH ¼ 7.3. However, in our hands
prodigiosene pharmacophore by way of the g-position. This key the reported 0.1 M Tris–HCl buffer was insufficient to maintain
coupling would result in the folate–prodigiosene conjugate as stable pH aer the addition of folic acid. Therefore, the initial
a single isomer, courtesy of the previous regiospecic activation buffer concentration was increased to 1 M and the pH subse-
of L-glutamic acid.62–65,68,69 To embark upon Strategy B, pteroic quently stabilised in the range of 7.2–7.3 via the addition of
acid was prepared following literature procedure through solid buffer. Aer 5 days, 1H NMR spectroscopic analysis of the
hydrolysis of folic acid using carboxypeptidase G in the crude product mixture revealed 75% conversion of folic acid to
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Scheme 2 Activation of folic acid with NHS and conjugation to linker-prodigiosenes 2a–c.
Attempts to couple 16 with the dithio linker-prodigiosene
conjugate 4c$HCl in the presence of HBTU and DMAP were
unsuccessful and only starting material was recovered (Scheme
5). However, coupling between 3b–c and the protected amino-
acid 16 successfully afforded substrates 18b–c, thus crucially
connecting the prodigiosene pharmacophore with the g-posi-
tion of L-glutamic acid, by way of a PEG linker. Boc-deprotection
in the presence of TsOH in a mixture of dioxane/water gave the
amines 19b–c. Strategy B (Fig. 4) then requires coupling of the
drug-appended glutamic acid moiety with the activated pteroic
acid, but attempts to couple 19b–c to 13 resulted in only partial
recovery of the substrate prodigiosenes 19b–c (Scheme 5).
In turning our attention to Strategy C (Fig. 4), the L-glutamic
acid derivative 16 was rst deprotected at the amino position,
and then coupled to the activated pteroic acid to successfully
afford 22. This g-carboxylic acid was then reacted with NHS to
give 23 which is activated in the desired position of what will
become folate (Scheme 6).65 The amines 2–4a–c were reacted
with a solution of 23, to provide conjugates 24–26a–c. Subse-
quently, the Teoc protecting group was removed with TBAF, and
the resulting tetrabutylammonium salt precipitated via the
addition of water. Dissolution of the salt in DMSO, followed by
reaction with NaOAc, afforded eight sodium folate–prodigio-
sene conjugates 27–28a–c and 29a–b. However, addition of
TBAF to 26c caused the cleavage of the S–S bond and the cor-
responding folate–prodigiosene conjugate 29c could not be
isolated (Scheme 6). Clearly the step-wise approach to building
folate acid, such that only the g-carboxyl site is available for
coupling, requires more synthetic effort that the direct
approach. However, in contrast to Strategy A, the step-wise
Scheme 3 Preparation of the activated Teoc-protected pteroic acid
13.
pteroic acid. The carboxylic acid of the crude pteroic acid was
activated using CDI and the primary amine then protected with
a trimethylsilylethoxycarbonyl (Teoc) group, to give 13 aer
purication using column chromatography on silica (Scheme
3). This purication also allowed the removal of folic acid
remaining from the initial step.
The L-glutamic acid moiety of folic acid was prepared from
its commercially available Boc-L-glutamic acid 5-benzyl ester
derivative (14), which was rst esteried at the a-position using
CDI and 2-(trimethylsilyl)ethanol, in order to obtain 15.
Subsequent hydrogenolysis of the benzyl ester at the g-position
gave the protected amino acid 16, ready for coupling with pro-
digiosene (Scheme 4).65
Scheme 4 Preparation of the protected glutamic acid derivative 16.
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Scheme 5 Attempts to synthesise Teoc-protected folic acid-prodigiosene conjugates 20.
approaches of Strategies B and C tolerate substantiation of involve evaluation of the cytotoxicity of the conjugates, along-
purity and characterization at each synthetic step and should side optimization of drug release and internalisation.
thus be the approaches adopted for the preparation of regioi-
somerically pure desired conjugates of folate.
Experimental section
All chemicals were purchased and used as received unless
otherwise indicated. Moisture sensitive reactions were per-
formed in oven-dried glassware and under a positive pressure of
Conclusions
nitrogen. Air- and moisture-sensitive compounds were intro-
In summary, the rst series of folate–prodigiosene conjugates
duced via syringe or cannula through a rubber septum. Flash
have been synthesised, and full characterisation acquired. In
chromatography was performed using either Silicycle ultra-pure
order to increase the lipophilicity, the water-solubility and the
silica (230–400 mm) or 150 mesh Brockmann III activated
ease of cleavage, three linkers were chosen to link the folate and
neutral/basic alumina oxide, as indicated. The NMR spectra
the prodigiosene moieties (DA, PEG and SS respectively). Cog-
were recorded using a 500 MHz spectrometer instrument using
nisant that the a-carboxylate of folate is involved in the inter-
CDCl3, MeOD or DMSO as solvents and are reported in part per
action with FRa, three synthetic approaches were investigated
million (ppm). Internal solvents were referenced at 7.26 ppm for
for the preparation of the targeted g-adduct. The direct and
1H and at 77.16 ppm for 13C when using CDCl3, at 3.31 ppm for
most commonly used literature method involves coupling the
1H and at 49.00 ppm for 13C when using MeOD and at 2.50 ppm
unprotected folic acid, activated in situ, to the amino-
for 1H and at 39.5 ppm for 13C when using DMSO-d6. Coupling
counterpart. Despite the widespread use of this direct
constants (J) are given in Hertz (Hz). Mass spectra were obtained
approach, oen presented along with unsubstantiated claims
using TOF and LCQ Duo ion trap instruments operating in ESI+/
as to purity and constitution of the product(s) thus obtained, we
ꢀ mode, as indicated. Compounds 1a–c,21 5–7,39,40,45 11,57 pteroic
determined it to be wholly unsatisfactory as it gives mixtures of
acid,65 13,65 15–16,65 and 21–23 (ref. 65) were prepared following
a- and g-regioisomers, along with various ureas and other
literature procedures.
synthetic intermediates presenting as impurities, which are
challenging to separate. We evaluated this shortcoming at the
activation stage, using simply NHS, as well as through reaction
General procedure 1 (GP1)
with octyl amine and the prodigiosene pharmacophore. In Amines 5–7 (2 eq.), HBTU (1.2 eq.) and DMAP (1.2 eq.) were
order to access the required g-adduct, the hydrolysis of folic added to a solution of prodigiosene 1 (1 eq.) in anhydrous
acid into its two core components (pteroic acid and L-glutamic CH2Cl2 (0.01 M) and the reaction mixture was stirred at room
acid) was necessary. The subsequent step-wise synthesis of folic temperature for 16 h under N2 atmosphere. The solvent was
acid, with the a-carboxylic acid protected, allowed synthesis of removed under reduced pressure and the crude mixture was
only the desired regioisomer thus, for the rst time, connecting partitioned between EtOAc and NaHCO3 (aq. sat solution). The
folic acid with the prodigiosene pharmacophore. Next steps will aqueous layer was extracted with EtOAc (ꢂ3). The combined
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Scheme 6 Synthesis of folate–prodigiosene conjugates 27–28a–c and 29a–b.
organic layers were washed with water (ꢂ5), brine, dried over HRMS (TOF) (m/z): [M + H]+ calcd for C27H36N5O5, 510.2711;
Na2SO4 and concentrated under reduced pressure.
(Z)-tert-Butyl (2-(4-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)
methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-4-oxobutanamido)
found, 510.2719.
(Z)-tert-Butyl (2-(6-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)
methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-6-oxohexanamido)
ethyl)carbamate (8a). Compound 8a was obtained according to ethyl)carbamate (8b). Compound 8b was obtained according to
GP1. The crude mixture was puried by column chromatog- GP1. The crude mixture was puried by column chromatog-
raphy using A2O3 type III basic (CH2Cl2 : MeOH 100 : 0, 99 : 1), raphy using A2O3 type III basic (CH2Cl2 : MeOH 100 : 0, 99 : 1),
followed by A2O3 type III neutral (CH2Cl2 : MeOH, 100 : 0, precipitated with CH2Cl2 : hexanes (1 : 9), ltered and washed
1
99 : 1) to afford 8a (0.098 g, 78%) as dark red glass. H NMR with hexanes to afford 8b (0.100 g, 87%) as orange glass. 1H
(CDCl3, 500 MHz) 1.41 (s, 9H), 2.21 (s, 3H), 2.38 (s, 3H), 2.47 (t, J NMR (CD3OD, 500 MHz) 1.42 (s, 9H), 1.68–1.70 (m, 4H), 2.22–
¼ 6.1 Hz, 2H), 3.02 (t, J ¼ 6.3 Hz, 2H), 3.24 (br s, 2H), 3.31 (br s, 2.26 (m, 2H), 2.39 (s, 3H), 2.66 (s, 3H), 2.81 (t, J ¼ 6.6 Hz, 2H),
2H), 3.96 (s, 3H), 5.14 (br s, 1H), 6.04 (s, 1H), 6.20–6.21 (m, 1H), 3.15 (t, J ¼ 6.0 Hz, 2H), 3.25 (t, J ¼ 6.1 Hz, 2H), 3.92 (s, 3H), 6.08
6.35 (br s, 1H), 6.72 (d, J ¼ 3.4 Hz, 1H), 6.76 (s, 1H), 6.89 (s, 1H). (s, 1H), 6.26–6.27 (m, 1H), 6.76 (s, 2H), 7.02 (s, 1H). 13C NMR
13C NMR (CDCl3, 125 MHz) 12.6, 14.6, 28.5, 29.8, 30.7, 38.3, (CD3OD, 125 MHz) 12.3, 15.4, 25.1, 26.7, 28.8, 30.2, 37.0, 40.5,
40.4, 58.7, 79.5, 96.1, 110.8, 111.9, 113.9, 122.7, 123.3, 126.4, 41.0, 43.1, 59.0, 96.7, 111.2, 111.3, 114.1, 123.6, 123.7, 128.3,
128.2, 129.8, 141.0, 142.8, 156.7, 160.9, 169.0, 173.7, 196.2. 128.8, 129.8, 142.6, 144.3, 162.1, 169.6, 176.3, 200.0 (1 carbon
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atom unaccounted for). HRMS (TOF) (m/z): [M + H]+ calcd for
(Z)-tert-Butyl (24-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)
methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-15,24-dioxo-4,7,10-
trioxa-14-azatetracosyl)carbamate (9c). Compound 9c was ob-
tained according to GP1. The crude mixture was puried by
column chromatography using Al2O3 type III basic
(EtOAc : hexanes 60 : 40, 80 : 20, EtOAc : MeOH 100 : 0, 99 : 1)
followed by Al2O3 type III neutral (EtOAc : hexanes 60 : 40,
80 : 20, EtOAc : MeOH 100 : 0, 99 : 1, 98 : 2) and Al2O3 type III
neutral (EtOAc 100%) to afford 9c as a red glass (0.200 g, 86%).
1H NMR (CDCl3, 500 MHz) 1.28 (br s, 8H), 1.43 (s, 9H), 1.56–1.63
(m, 4H), 1.75 (quint., J ¼ 6.0 Hz, 4H), 2.12 (t, J ¼ 7.5 Hz, 2H), 2.20
(s, 3H), 2.39 (s, 3H), 2.63 (t, J ¼ 7.5 Hz, 2H), 3.19–3.23 (m, 2H),
3.34 (q, J ¼ 6.0 Hz, 2H), 3.49–3.64 (m, 12H), 3.97 (s, 3H), 4.97
(br s, 1H), 6.04 (s, 1H), 6.19–6.21 (m, 2H), 6.72 (d, J ¼ 3.6 Hz,
1H), 6.75 (br s, 1H), 6.91 (s, 1H). 13C NMR (CDCl3, 125 MHz)
12.4, 14.1, 24.3, 25.9, 28.6, 29.1, 29.3, 29.4, 29.5, 29.8, 36.9, 38.0,
38.6, 42.8, 58.6, 69.7, 70.3 (ꢂ2), 70.6, 70.7, 77.4, 77.6, 79.0, 96.1,
110.7, 112.1, 113.8, 123.3, 126.2, 128.3, 129.6, 140.5, 142.1,
156.2, 160.9, 169.0, 173.2, 198.2 (1 carbon atom unaccounted
for). HRMS (TOF) (m/z): [M + Na]+ calcd for C41H63N5Na1O8,
776.4569; found, 776.4558.
(Z)-tert-Butyl (2-((2-(4-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-
5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-4-oxobutanamido)
ethyl)disulfanyl)ethyl)carbamate (10a). Compound 10a was ob-
tained according to GP1. The crude mixture was puried by
column chromatography using Al2O3 type III neutral
(EtOAc : hexanes 20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40, 70 : 50,
100 : 0, EtOAc : MeOH 99 : 1) to afford 10a as a red glass
(0.052 g, 72%). 1H NMR (CDCl3, 300 MHz) 1.43 (s, 9H), 2.28 (s,
3H), 2.38 (s, 3H), 2.55 (t, J ¼ 6.4 Hz, 2H), 2.75–2.82 (m, 4H), 3.04
(t, J ¼ 6.4 Hz, 2H), 3.41–3.45 (m, 2H), 3.55 (q, J ¼ 6.4 Hz, 2H),
3.97 (s, 3H), 5.05 (br s, 1H), 6.03 (s, 1H), 6.23 (dd, J ¼ 3.6, 2.4 Hz,
1H), 6.54 (t, J ¼ 5.1 Hz, 1H), 6.23 (dd, J ¼ 3.6, 2.4 Hz, 1H), 6.52–
6.56 (m, 1H), 6.73 (dd, J ¼ 3.6, 1.2 Hz, 1H), 6.81 (br s, 1H), 6.88
(s, 1H). 13C NMR (CDCl3, 125 MHz) 12.6, 14.5, 28.5, 30.5, 38.2,
38.4, 39.6, 58.6, 77.4, 79.7, 96.0, 110.8, 111.9, 113.9, 122.7, 123.5,
126.3, 128.1, 130.0, 140.5, 142.8, 156.0, 160.7, 168.9, 173.2, 195.9
(1 carbon atom unaccounted for). HRMS (TOF) (m/z): [M + H]+
calcd for C29H40N5O5S2, 602.2465; found, 602.2456.
C
29H40N5O5, 538.3024; found, 538.3012.
(Z)-tert-Butyl (2-(10-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-
yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-10-oxodecanamido)
ethyl)carbamate (8c). Compound 8c was obtained according to
GP1. The crude mixture was puried by column chromatog-
raphy using Al2O3 type III neutral (EtOAc 100%) followed by
Al2O3 type III neutral (CH2Cl2 : MeOH 99 : 1) and Al2O3 type III
basic (CH2Cl2 : MeOH 99.5 : 0.5, 99 : 1, 98.5 : 0.5) to afford 8c as
1
a red glass (0.116 g, 63%). H NMR (CDCl3, 300 MHz) 1.26 (s,
8H), 1.42 (s, 9H), 1.58–1.60 (m, 4H), 2.10–2.13 (m, 5H), 2.38 (s,
3H), 2.62 (t, J ¼ 7.2 Hz, 2H), 3.24 (br s, 2H), 3.31 (br s, 2H), 3.97
(s, 3H), 5.05 (br s, 1H), 6.06 (s, 1H), 6.18 (s, 1H), 6.25 (br s, 1H),
6.71–6.72 (s, 2H), 6.93 (s, 1H). 13C NMR (CDCl3, 100 MHz) 12.4,
14.0, 24.3, 25.8, 28.5, 29.2, 29.3, 29.4, 36.8, 40.5, 40.7, 42.8, 58.7,
79.7, 96.1, 110.7, 112.1, 113.8, 123.4, 123.6, 126.2, 128.3, 129.7,
132.3, 140.5, 142.2, 157.1, 161.1, 169.1, 174.0, 198.3. HRMS
(TOF) (m/z): [M + Na]+ calcd for C33H47N5NaO5, 616.3436; found,
616.3490.
(Z)-tert-Butyl (18-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)
methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-15,18-dioxo-4,7,10-
trioxa-14-azaoctadecyl)carbamate (9a). Compound 9a was ob-
tained according to GP1. The crude mixture was puried by
column chromatography using Al2O3 type III basic
(EtOAc : hexanes 50 : 50, 70 : 30 EtOAc 100 : 0, CH2Cl2 : MeOH
100 : 0, 99 : 1) to afford 9a as an orange glass (0.124 g, 74%). 1H
NMR (CDCl3, 500 MHz) 1.42 (s, 9H), 1.73–1.79 (m, 4H), 2.25
(br s, 3H), 2.38 (s, 3H), 2.49 (t, J ¼ 6.5 Hz, 2H), 3.02 (t, J ¼ 6.5 Hz,
2H), 3.19–3.20 (m, 2H), 3.34 (q, J ¼ 6.0 Hz, 2H), 3.51–3.59 (m,
8H), 3.62–3.64 (m, 4H), 3.96 (s, 3H), 5.02 (br s, 1H), 6.02 (s, 1H),
6.22 (br s, 1H), 6.42 (br s, 1H), 6.72 (br s, 1H), 6.78 (br s, 1H), 6.88
(s, 1H). 13C NMR (CDCl3, 125 MHz) 12.5, 14.7, 28.6, 29.1, 29.8,
30.5, 37.8, 38.2, 38.6, 58.6, 69.6, 69.9, 70.3 (ꢂ2), 70.6, 79.0, 95.9,
110.8, 111.9, 113.8, 122.8, 123.4, 126.4, 128.2, 129.9, 140.7,
142.6, 156.2, 160.6, 168.8, 172.8, 196.0 (1 carbon atom unac-
counted for). HRMS (TOF) (m/z): [M
35H51N5Na1O8, 692.3630; 692.3627.
(Z)-tert-Butyl (20-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)
+
Na]+ calcd for
C
methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-15,20-dioxo-4,7,10-
trioxa-14-azaicosyl)carbamate (9b). Compound 9b was obtained
according to GP1. The crude mixture was puried by column
chromatography using A2O3 type III neutral (hexanes : EtOAc
50 : 50, 40 : 60, 30 : 70, 20 : 80, 10 : 90, 0 : 100, then CH2Cl2-
: MeOH 99 : 1), followed by twice A2O3 type III basic (CH2Cl2-
: MeOH, 100 : 0, 99 : 1) to afford 9b (0.104 g, 64%) as dark red
solid. 1H NMR (CDCl3, 500 MHz) 1.42 (s, 9H), 1.63–1.66 (m, 4H),
1.70–1.80 (m, 4H), 2.14–2.19 (m, 5H), 2.38 (s, 3H), 2.65–2.69 (m,
2H), 3.19 (d, J ¼ 5.5 Hz, 2H), 3.34 (dd, J ¼ 12.0 and 6.0 Hz, 2H),
3.48–3.62 (m, 12H), 3.97 (s, 3H), 5.02 (m, 1H), 6.04 (s, 1H), 6.19–
6.21 (m, 1H), 6.39 (br s, 1H), 6.72 (d, J ¼ 3.6 Hz, 1H), 6.76 (s, 1H),
6.91 (s, 1H). 13C NMR (CDCl3, 125 MHz) 12.3, 13.9, 23.7, 25.4,
28.5, 29.1, 29.7, 36.6, 37.8, 38.5, 42.3, 58.6, 70.0, 70.2 (ꢂ2), 70.6,
78.9, 96.1, 110.6, 111.9, 113.9, 123.3, 123.5, 126.1, 128.1, 129.7,
140.3, 142.3, 156.2, 161.0, 169.1, 172.9, 197.5 (2 carbon atoms
unaccounted for). HRMS (TOF) (m/z): [M + H]+ calcd for
(Z)-tert-Butyl (2-((2-(6-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-
5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-6-oxohexanamido)
ethyl)disulfanyl)ethyl)carbamate (10b). Compound 10b was
obtained according to GP1. The crude mixture was puried by
column chromatography using Al2O3 type III neutral
(EtOAc : hexanes 20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40, 70 : 30,
100 : 0 then EtOAc : MeOH 99/1) to afford 10b as a red-brown
1
glass (0.090 g, 75%). H NMR (CDCl3, 300 MHz) 1.43 (s, 9H),
1.66–1.68 (m, 4H), 2.21–2.26 (m, 5H), 2.39 (s, 3H), 2.69 (t, J ¼
6.3 Hz, 2H), 2.75 (t, J ¼ 6.6 Hz, 2H), 2.82 (t, J ¼ 6.3 Hz, 2H), 3.37–
3.43 (m, 2H), 3.55 (q, J ¼ 6.1 Hz, 2H), 3.98 (s, 3H), 5.02 (br s, 1H),
6.05 (s, 1H), 6.21 (dd, J ¼ 3.6, 2.4 Hz, 1H), 6.59 (br s, 1H), 6.73
(dd, J ¼ 3.6, 1.2 Hz, 1H), 6.77 (br s, 1H), 6.92 (s, 1H). 13C NMR
(CDCl3, 125 MHz) 12.4, 14.0, 23.7, 25.3, 28.5, 36.4, 38.0, 38.3,
38.4, 39.6, 42.3, 58.7, 79.7, 96.2, 110.7, 112.0, 114.0, 123.5, 126.2,
128.2, 129.7, 140.5, 142.3, 156.0, 161.1, 169.1, 173.3, 197.6 (1
C
37H55N5NaO5, 698.4123; found, 698.4102.
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carbon atom unaccounted for). HRMS (TOF) (m/z): [M + H]+ 43.1, 59.00, 96.7, 111.2, 111.3, 114.1, 123.5, 123.7, 128.2, 128.9,
calcd for C31H44N5O5S2, 630.2778; found, 630.2770. 129.8, 142.7, 144.2, 162.0, 169.6, 176.6, 199.9. HRMS (TOF) (m/
(Z)-tert-Butyl (2-((2-(10-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]- z): [M + H]+ calcd for C24H32N5O3, 438.2500; found, 438.2488.
5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-10-
oxodecanamido)ethyl)disulfanyl)ethyl)carbamate
(Z)-N-(2-Aminoethyl)-10-(2-((4-methoxy-1H,10H-[2,20-bipyr-
(10c). rol]-5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-10-
Compound 10c was obtained according to GP1. The crude oxodecanamide (2c). A solution of 8c (0.073 g, 0.12 mmol) in
mixture was puried by column chromatography using Al2O3 a mixture of CHCl3 : MeOH (1 : 1, 6 mL) was treated with HCl
type III basic (EtOAc : hexanes 50 : 50, 70 : 30 EtOAc 100%) 12 N (0.024 mL, 0.29 mmol) and the reaction mixture was stirred
followed by Al2O3 type III neutral (EtOAc : hexanes 50 : 50, 60/ at room temperature for 7 h. The solvent was removed under
40) to afford 10c as a red glass (0.138 g, 65%). 1H NMR vacuum and NaOH (10% aq. solution) was added drop-wise
(CDCl3, 300 MHz) 1.28 (s, 8H), 1.43 (s, 9H), 1.58–1.62 (m, 4H), under stirring until the red solution turned orange-brown.
2.14 (s, 3H), 2.18 (t, J ¼ 7.4 Hz, 2H), 2.39 (s, 3H), 2.62 (t, J ¼ The solvent was removed under vacuum and the precipitate
7.4 Hz, 2H), 2.75 (t, J ¼ 6.7 Hz, 2H), 2.81 (t, J ¼ 5.8 Hz, 2H), 3.39– was washed with water to give a dark red solid (0.066 g, 76%).
3.43 (m, 2H), 3.54 (q, J ¼ 6.1 Hz, 2H), 3.98 (s, 3H), 5.06 (br s, 1H), Mp 88 ꢁC. 1H NMR (DMSO-d6, 500 MHz) 1.22–1.32 (m, 8H),
6.06 (s, 1H), 6.18 (t, J ¼ 3.0 Hz, 1H), 6.41 (br s, 1H), 6.72 (d, J ¼ 1.47–1.49 (m, 2H), 1.56–1.59 (m, 2H), 2.03–2.06 (m, 2H), 2.34 (s,
3.0 Hz, 2H), 6.93 (s, 1H). 13C NMR (CDCl3, 100 MHz) 12.4, 14.0, 3H), 2.67 (s, 3H), 2.72–2.74 (m, 2H), 2.99–3.03 (m, 2H), 3.25–3.35
24.3, 25.8, 28.5, 29.3, 29.5, 36.7, 37.9, 38.2, 38.6, 39.7, 42.8, 58.7, (m, 2H), 3.88 (s, 3H), 6.19 (s, 1H), 6.25 (s, 1H), 6.70 (s, 1H), 6.79
79.7, 96.1, 110.7, 112.1, 113.9, 123.4, 123.6, 126.2, 128.2, 129.8, (s, 1H), 7.14 (s, 1H), 7.68 (br s, 1H), 11.81 (br s, 1H). 13C NMR
140.3, 142.2, 156.1, 161.0, 169.1, 173.7, 198.2 (2 carbon atoms (DMSO-d6, 125 MHz) 11.7, 15.3, 23.7, 25.3, 28.6, 28.7, 28.8, 28.9,
unaccounted for). HRMS (TOF) (m/z): [M + H]+ calcd for 35.4, 41.4, 41.8, 42.2, 58.4, 96.2, 110.1 (2C), 113.0, 122.4, 122.9,
C
35H52N5O5S2, 686.3404; found, 686.3386.
126.3, 127.4, 128.2, 140.6, 142.1, 159.3, 167.3, 172.1, 196.6.
(Z)-N-(2-Aminoethyl)-4-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]- HRMS (TOF) (m/z): [M + H]+ calcd for C28H40N5O3, 494.3126;
5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-4-oxobutanamide
(2a). A solution of 8a (0.038 g, 0.070 mmol) in MeOH (1 mL) was
found, 494.3129.
(Z)-N-(3-(2-(2-(3-Aminopropoxy)ethoxy)ethoxy)propyl)-4-(2-
treated with HCl (1.2 mL, 2 M solution in Et2O, 2.40 mmol) and ((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-
the reaction mixture was stirred at room temperature for 18 h. dimethyl-2H-pyrrol-4-yl)-4-oxobutanamide (3a). A solution of 9a
The solvent was removed under reduced pressure and the crude (0.125 g, 0.18 mmol) in a mixture of MeOH/CHCl3 (1 : 1, 4 mL)
mixture was dissolved in MeOH (1.5 mL). NaOH (10% aq. was treated with HCl 12 N (0.031 mL, 0.37 mmol) at room
solution) was added to the solution until a colour change temperature. Aer 30 min additional HCl 12 N (0.030 mL, 0.36
occurred (dark red to orange). The solvent was removed under mmol) was added and the reaction mixture stirred for an
reduced pressure and the precipitate was ltered and washed additional 3 hours. The solvent was removed under reduced
with H2O to afford 2a (0.023 g, 80%) as orange solid. Mp 119 ꢁC. pressure and the crude mixture was dissolved in MeOH (2 mL).
1H NMR (DMSO-d6, 500 MHz) 2.36 (s, 3H), 2.41 (t, J ¼ 6.7 Hz, NaOH (10% aq. solution) was added drop-wise under stirring
2H), 2.56 (t, J ¼ 6.3 Hz, 2H), 2.69 (s, 3H), 2.99 (t, J ¼ 6.8 Hz, 2H), until the red solution turned orange-brown. The solvent was
3.05 (dd, J ¼ 12.1, 6.2 Hz, 2H), 3.88 (s, 3H), 6.19 (s, 1H), 6.25 removed under vacuum and the crude solid was puried using
(br s, 1H), 6.70 (s, 1H), 6.79 (br d, 1H, J ¼ 3.4 Hz), 7.14 (br s, 1H), ash chromatography on Al2O3 basic type III (EtOAc 100%,
7.78–7.79 (m, 1H), 11.81 (s, 1H). 13C NMR (DMSO-d6, 125 MHz) CH2Cl2 : MeOH 98 : 2, 95 : 5, 90 : 10 then MeOH 100%) to
11.8, 15.4, 29.4, 37.3, 41.4, 42.4, 58.5, 96.3, 110.1 (2C), 113.1, afford 3a as a dark red glass (0.105 g, 51%). 1H NMR (CDCl3, 500
122.1, 122.9, 126.3, 127.5, 128.2, 140.8, 142.1, 159.4, 167.3, MHz) 1.68–1.73 (m, 4H), 2.20 (s, 3H), 2.34 (s, 3H), 2.48 (t, J ¼
171.6, 195.3 (1 carbon atom unaccounted for). HRMS (TOF) (m/ 6.5 Hz, 2H), 2.84 (t, J ¼ 6.5 Hz, 2H), 2.97 (t, J ¼ 6.5 Hz, 2H), 3.28
z): [M + H]+ calcd for C22H28N5O3, 410.2187; found, 410.2177.
(Z)-N-(2-Aminoethyl)-6-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]- 6.18–6.19 (s, 1H), 6.68–6.71 (m, 2H), 6.76 (s, 1H), 6.86 (s, 1H).
5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-yl)-6-oxohexanamide
13C NMR (CDCl3, 125 MHz) 12.5, 14.5, 29.3, 30.4, 30.7, 37.4,
(q, J ¼ 6.5 Hz, 2H), 3.47–3.60 (m, 12H), 3.95 (s, 3H), 6.03 (s, 1H),
(2b). A solution of 8b (0.100 g, 0.186 mmol) in a mixture of 38.0, 40.1, 58.6, 69.3, 69.9, 70.0 (ꢂ2), 70.2, 70.5, 96.0, 110.7,
MeOH : CHCl3 (1 : 1, 4 mL) was treated with HCl (3.3 mL, 2 M 111.7, 113.9, 122.7, 123.5, 126.4, 128.1, 129.8, 140.6, 142.7,
solution in Et2O, 6.60 mmol) and the reaction mixture was 160.7, 168.9, 173.2, 196.1. HRMS (TOF) (m/z): [M + H]+ calcd for
stirred at room temperature for 18 h. The solvent was removed
under reduced pressure and the crude mixture was dissolved in
C
30H44N5O6, 570.3286; found, 570.3295.
N-(3-(2-(2-(3-Aminopropoxy)ethoxy)ethoxy)propyl)-6-(2-((4-
MeOH (3.8 mL). NaOH (10% aq. solution) was added to the methoxy-1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-dimethyl-
solution until a colour change occurred (dark red to orange). 2H-pyrrol-4-yl)-6-oxohexanamide (3b). A solution of 9b (0.104 g,
The solvent was removed under reduced pressure and the 0.150 mmol) in a mixture of MeOH : CHCl3 (1 : 1, 3.4 mL) was
precipitate was ltered and washed with H2O to afford 2b treated with HCl 12 N (0.55 mL, 6.60 mmol) and the reaction
(0.076 g, 93%) as orange solid. 1H NMR (CD3OD, 500 MHz) mixture was stirred at room temperature for 25 h. The solvent
1.68–1.72 (m, 4H), 2.24–2.27 (m, 2H), 2.40 (s, 3H), 2.66 (s, 3H), was removed under reduced pressure and the crude mixture
2.79–2.83 (m, 2H), 3.28–3.32 (m, 2H), 3.92 (s, 3H), 6.08 (s, 1H), was dissolved in MeOH (2 mL). NaOH (6 M aq. solution) was
6.25–6.27 (m, 1H), 6.76–6.78 (m, 2H), 7.02–7.03 (m, 1H). 13C added to the solution until a colour change occurred (dark red
NMR (CD3OD, 125 MHz) 12.3, 15.4, 25.1, 26.6, 37.0, 41.5, 41.7, to orange). The solvent was removed under reduced pressure
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and the crude mixture was puried using ash chromatography 173.1, 196.0 (1 carbon atom unaccounted for). HRMS (TOF) (m/
on Al2O3 basic type III (CH2Cl2 : MeOH, 9 : 1) to afford 3b z): [M + H]+ calcd for C24H32N5O3S2, 502.1941; found, 502.1933.
1
(0.074 g, 83%) as a dark red glass. H NMR (CDCl3, 500 MHz) HRMS (TOF) (m/z): [M + H]+ calcd for C24H32N5O3S2, 502.1933;
1.63 (br s, 4H), 1.66–1.71 (m, 2H), 1.72–1.77 (m, 2H), 2.15 (s, found, 502.1941.
3H), 2.17 (br s, 2H), 2.37 (s, 3H), 2.65 (br s, 2H), 2.76 (t, 2H, J ¼
(S,Z)-2-(Trimethylsilyl)ethyl 2-((tert-butoxycarbonyl)amino)-
6.6 Hz), 3.30–3.34 (m, 2H), 3.52 (t, 4H, J ¼ 5.8 Hz), 3.56 (ddd, 25-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-
12H, J ¼ 24.1, 10.1, 8.0 Hz), 3.96 (s, 3H), 6.04 (s, 1H), 6.18–6.19 dimethyl-2H-pyrrol-4-yl)-20,25-dioxo-9,12,15-trioxa-5,19-
(m, 1H), 6.63 (br s, 1H), 6.71 (d, 1H, J ¼ 3.5 Hz), 6.74 (br s, 1H), diazapentacosan-1-oate (18b). Compound 3b was obtained
6.91 (s, 1H). 13C NMR (CDCl3, 125 MHz) 12.4, 14.0, 23.8, 25.5, following GP1. The crude mixture was puried using Al2O3 type
29.1, 29.8, 31.0, 33.3, 36.7, 37.7, 39.7, 42.4, 58.6, 69.6, 69.9, 70.2, III neutral (CH2Cl2 100%, CH2Cl2/MeOH 99/1, 98/2) followed by
70.6, 96.2, 110.7, 112.0, 113.9, 123.4 (ꢂ2), 126.2, 128.2, 129.7, Al2O3 type III basic (CH2Cl2 100%, CH2Cl2/MeOH 99/1) to afford
140.5, 142.3, 161.1, 169.1, 173.0, 197.6. HRMS (TOF) (m/z): [M + 18b as a red glass (0.020 g, 20%). 1H NMR (CDCl3, 300 MHz) 0.02
H]+ calcd for C32H48N5O6, 598.3599; found, 598.3577.
N-(3-(2-(2-(3-aminopropoxy)ethoxy)ethoxy)propyl)-10-(2-((4-
methoxy-1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-dimethyl-
(s, 9H), 0.95–1.01 (m, 2H), 1.42 (s, 9H), 1.65–1.67 (m, 4H), 1.73–
1.81 (m, 4H), 1.87–1.95 (m, 1H), 2.08–2.13 (m, 1H), 2.16–2.20
(m, 3H), 2.26 (s, 3H), 2.39 (s, 3H), 2.67–2.69 (m, 2H), 3.31–3.37
2H-pyrrol-4-yl)-10-oxodecanamide (3c). A solution of 9c (0.113 g, (m, 4H), 3.51–3.64 (m, 12H), 3.96 (s, 3H), 4.14–4.20 (m, 3H), 5.44
0.150 mmol) in a mixture of MeOH : CHCl3 (1 : 1, 3.2 mL) was (d, 1H, J ¼ 8.1 Hz), 6.02 (s, 1H), 6.22 (dd, 1H, J ¼ 3.6, 2.7 Hz),
treated with HCl 12 N (0.65 mL of 12 M aqueous solution, 7.80 6.45 (br s, 1H), 6.59 (br s, 1H), 6.72 (dd, 1H, J ¼ 3.6, 1.2 Hz), 6.79
mmol) and the reaction mixture was stirred at room tempera- (br s, 1H), 6.89 (s, 1H). 13C NMR (CDCl3, 125 MHz), ꢀ1.4 (3C),
ture for 5 h. The solvent was removed under reduced pressure 12.5, 14.7, 17.5, 23.9, 25.5, 28.5 (3C), 28.8, 29.2, 29.8, 32.8, 36.7,
and the crude mixture was dissolved in MeOH (2 mL). NaOH 37.8, 37.9, 42.4, 53.5, 58.6, 63.9, 70.0 (ꢂ2), 70.2, 70.6 (4C), 80.0,
(2 M aq. solution) was added to the solution until a colour 96.0, 110.8, 111.9, 113.6, 123.1, 123.3, 126.6, 128.4, 129.3, 141.2,
change occurred (dark red to orange). The solvent was removed 141.9, 156.0, 160.8, 168.9, 172.1, 172.6, 173.0, 197.6. HRMS
under reduced pressure and the crude mixture was puried by (TOF) (m/z): [M + Na]+ calcd for C47H74N6Na1O11Si1, 949.5077;
ash chromatography using Al2O3 basic type III (CH2Cl2- found, 949.5086.
: MeOH, 9 : 1) to afford 3c (0.068 g, 70%) as a dark red glass. 1H
(S,Z)-2-(Trimethylsilyl)ethyl 2-((tert-butoxycarbonyl)amino)-
NMR (CDCl3, 500 MHz) 1.24–1.27 (m, 8H), 1.56–1.60 (m, 4H), 29-(2-((4-methoxy-1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-
1.63 (br s, 4H), 1.65–1.79 (m, 4H), 2.11 (d, 2H, J ¼ 7.8 Hz), 2.15 dimethyl-2H-pyrrol-4-yl)-20,29-dioxo-9,12,15-trioxa-5,19-
(s, 3H), 2.38 (s, 3H), 2.62 (t, 2H, J ¼ 7.4 Hz), 2.77 (t, 2H, J ¼ 6.7 diazanonacosan-1-oate (18c). Compound 3c was obtained
Hz), 3.33 (dd, 2H, J ¼ 12.2, 6.0 Hz), 3.51–3.63 (m, 12H), 3.97 (s, following GP1. The crude mixture was puried using Al2O3 type
3H), 6.05 (s, 1H), 6.17–6.19 (m, 1H), 6.39–6.43 (br m, 1H), 6.70– III basic (EtOAc 100%, EtOAc/MeOH 99/1, CH2Cl2/MeOH 98/2),
6.73 (m, 2H), 6.92 (s, 1H). 13C NMR (CDCl3, 125 MHz) 12.4, 14.1, followed by Al2O3 type III basic (CH2Cl2/MeOH 99/1) and Al2O3
24.3, 25.9, 29.1, 29.3, 29.4, 29.5, 33.4, 36.9, 37.8, 39.8, 58.6, 69.6 type III neutral (CH2Cl2/MeOH 99/1, 98/2) to afford 18c as a red
1
(2C), 70.1, 70.3 (2C), 70.7, 96.1, 110.7, 112.1, 113.8, 123.3, 123.6, glass (0.130 g, 46%). H NMR (CDCl3, 300 MHz) 0.03 (s, 9H),
126.2, 128.2, 129.7, 140.4, 142.2, 160.9, 169.1, 173.2, 198.1 (2 0.96–1.02 (m, 2H), 1.28 (s, 8H), 1.43 (s, 9H), 1.59–1.62 (m, 4H),
carbons uncounted for). HRMS (TOF) (m/z): [M + H]+ calcd for 1.76 (quint., 4H, J ¼ 6.0 Hz), 1.87–1.97 (m, 1H), 2.12 (t, 3H, J ¼
C
36H56N5O6, 654.4225; found, 654.4203.
(Z)-N-(2-((2-Aminoethyl)disulfanyl)ethyl)-4-(2-((4-methoxy-
7.5 Hz), 2.21–2.26 (m, 5H), 2.39 (s, 3H), 2.64 (t, 2H, J ¼ 7.3 Hz),
3.33 (q, 4H, J ¼ 6.0 Hz), 3.52–3.64 (m, 12H), 3.96 (s, 3H), 4.16–
1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4- 4.21 (m, 3H), 5.43 (d, 1H, J ¼ 8.1 Hz), 6.03 (s, 1H), 6.21–6.23 (m,
yl)-4-oxobutanamide (4a). A solution of 10a (0.052 g, 0.077 2H), 6.56 (br s, 1H), 6.71–6.73 (m, 1H), 6.79 (br s, 1H), 6.91 (s,
mmol) in a mixture of MeOH : CHCl3 (1 : 1, 4 mL) was treated 1H). 13C NMR (CDCl3, 100 MHz), ꢀ1.4 (3C), 12.4, 14.3, 17.5,
with HCl 12 N (0.024, 0.077 mmol). The reaction was stirred 24.3, 25.9, 28.4 (3C), 28.8, 29.1, 29.2, 29.3, 29.4, 29.5, 32.8, 36.9,
overnight at room temperature and additional HCl 12 N (0.024, 37.7, 37.9, 42.8, 53.5, 58.6, 63.9, 69.9, 70.1, 70.5 (4C), 77.4, 77.6,
0.077 mmol) was added. The solution was concentrated under 80.0, 96.0, 110.8, 112.1, 113.8, 123.3, 123.5, 126.3, 128.2, 129.7,
reduced pressure and the crude mixture dissolved in MeOH (3 142.1, 155.9, 168.9, 172.1, 172.6, 173.4, 198.2. HRMS (TOF) (m/
mL). NaOH (10% aq. solution) was added dropwise under stir- z): [M + Na]+ calcd for C51H82N6Na1O11Si1, 1005.5703; found,
ring until the red solution turned orange-brown. The solvent 1005.5713.
was removed under vacuum and the crude solid was puried
(S,Z)-2-(Trimethylsilyl)ethyl
2-amino-25-(2-((4-methoxy-
using ash chromatography on Al2O3 basic type III (EtOAc 1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4-
100%, CH2Cl2 : MeOH, 95 : 5) to afford 4a as a dark red glass yl)-20,25-dioxo-9,12,15-trioxa-5,19-diazapentacosan-1-oate
1
(0.033 g, 77%) H NMR (CDCl3, 300 MHz) 2.25 (s, 3H), 2.38 (s, (19b). Prodigiosene 18b (0.020 g, 0.021 mmol) was dissolved in
3H), 2.53 (t, J ¼ 6.3 Hz), 2.73–2.80 (m, 4H), 2.97–3.05 (m, 4H), a mixture of dioxane : water (1 : 1, 1 mL) and PTSA (0.016 g,
3.56 (q, J ¼ 6.8 Hz, 2H), 3.97 (s, 3H), 6.03 (s, 1H), 6.22 (dd, J ¼ 0.052 mmol) was added. The reaction was stirred at 60 ꢁC for 3
3.8, 2.7 Hz, 1H), 6.38 (t, J ¼ 5.7 Hz, 1H), 6.73 (dd, J ¼ 3.8, 1.2 Hz, hours and additional PTSA (0.016 g, 0.052 mmol) was added.
1H), 6.79 (s, 1H), 6.89 (s, 1H). 13C NMR (CDCl3, 125 MHz) 12.6, Aer 16 h the solvent was removed under reduced pressure the
14.8, 30.6, 38.0, 38.2, 38.5, 40.8, 42.7, 58.7, 96.0, 110.9, 111.9, crude solid was puried using Al2O3 type III basic (CH2Cl2/
113.8, 122.7, 123.2, 126.5, 128.2, 129.8, 142.6, 160.7, 168.9, MeOH 99/1) to afford 19b as an orange glass (0.011 g, 64%). 1H
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NMR (CDCl3, 300 MHz) 0.04 (s, 9H), 0.96–1.02 (m, 2H), 1.65– 26.4, 28.2, 29.5, 31.8, 37.3 (2C), 46.0, 52.3, 58.4, 62.4, 64.1, 77.6,
1.68 (m, 4H), 1.73–1.82 (m, 5H), 2.04–2.13 (m, 1H), 2.15–2.29 96.3, 110.1, 111.2 (2C), 113.1, 121.3, 122.1, 122.9, 126.4, 127.5,
(m, 2H), 2.32–2.40 (m, 2H), 2.68 (s, 3H), 2.72 (s, 3H), 3.30–3.43 128.2, 129.0 (2C), 129.8, 140.9, 142.2, 148.9, 150.7, 151.4, 154.9,
(m, 2H), 3.50–3.64 (m, 5H), 3.96 (s, 3H), 4.15–4.21 (m, 2H), 6.01 155.3, 155.6, 159.5, 160.9, 166.4, 167.4, 171.6, 171.8, 172.3,
(s, 1H), 6.23–6.25 (m, 1H), 6.45 (t, 1H, J ¼ 5.1 Hz), 6.51 (t, 1H, J ¼ 195.3. HRMS (TOF) (m/z): [M + H]+ calcd for C52H69N12NaO10Si2,
4.8 Hz), 6.72 (d, 1H, J ¼ 3.6 Hz), 6.84 (br s, 1H), 6.89 (s, 1H). 13
C
1077.4793; found, 1077.4748.
NMR (CDCl3, 100 MHz), ꢀ1.4 (3C), 12.5, 14.9, 17.6, 23.9, 25.5,
Teoc-FA-DA-prod(C4) (24b). Compound 24b was obtained
29.2, 29.3, 30.5, 33.0, 36.7, 37.8, 42.4, 54.2, 58.6, 63.5, 70.0, 70.1, according to GP2 as orange solid (0.096 g, 84%). Mp 138–140 ꢁC.
70.2, 70.6 (4C), 95.9, 110.8, 111.9, 113.5, 123.0, 123.2, 126.7, 1H NMR (DMSO-d6, 500 MHz) 0.00 (s, 9H), 0.05 (s, 9H), 0.86–
128.4, 129.2, 141.4, 141.7, 160.6, 168.8, 172.5, 173.0, 175.9, 0.87 (m, 3H), 0.91–0.94 (m, 2H), 1.02–1.05 (m, 3H), 1.24–1.28
197.6.0. HRMS (TOF) (m/z): [M + Na]+ calcd for C42H66N6Na1- (m, 1H), 1.36 (br s, 3H), 1.54 (br s, 4H), 1.91–2.07 (m, 4H), 2.18
O9Si1, 849.4553; found, 849.4557.
(br s, 2H), 2.34 (s, 3H), 2.67 (s, 3H), 2.72 (br s, 2H), 3.06 (m, 4H),
(S,Z)-2-(Trimethylsilyl)ethyl
2-amino-29-(2-((4-methoxy- 3.87 (s, 3H), 4.09–4.12 (m, 2H), 4.28–4.29 (m, 2H), 4.58 (br s,
1H,10H-[2,20-bipyrrol]-5-yl)methylene)-3,5-dimethyl-2H-pyrrol-4- 3H), 6.18 (s, 1H), 6.24 (s, 1H), 6.65 (br d, 2H, J ¼ 7.0 Hz), 6.68 (s,
yl)-20,29-dioxo-9,12,15-trioxa-5,19-diazanonacosan-1-oate (19c). 1H), 6.78 (br s, 1H), 6.99 (br s, 1H), 7.13 (s, 1H), 7.65 (br d, 2H, J
Prodigiosene 18c (0.130 g, 0.13 mmol) was dissolved in ¼ 7.0 Hz), 7.77 (br s, 1H), 7.85 (br s, 1H), 8.28–8.31 (m, 1H), 8.81
a mixture of dioxane : water (1 : 1, 6 mL) and PTSA (0.063 g, 0.32 (s, 1H), 11.55 (br s, 2H), 11.81 (br s, 1H). 13C NMR (DMSO-d6,
mmol) was added. The reaction was stirred at 60 ꢁC for 3 hours 125 MHz), ꢀ1.5 (6C), 11.8, 15.4, 16.9, 17.1, 23.4, 25.0, 26.4, 28.2,
and additional PTSA (0.063 mg, 0.32 mmol) was added. Aer 31.8, 35.5, 38.3, 38.5, 41.6, 46.0, 52.3, 58.4, 62.4, 64.6, 79.2, 96.2,
16 h the reaction mixture was quenched by addition of NaHCO3 110.1, 111.3, 113.0, 121.4, 122.3, 122.9, 126.3, 127.5, 128.2,
solid until the dark red solution turned dark brown. The solvent 128.7, 129.1, 129.9, 140.8, 142.2, 149.1, 149.2, 150.7, 151.9,
were removed under vacuum and the crude solid was puried 154.5, 155.0, 159.4, 159.6, 166.4, 167.4, 171.6, 172.2, 172.3,
using Al2O3 type III basic (CH2Cl2/MeOH 98/2, 95/5) to afford 196.4. HRMS (TOF) (m/z): [M + H]+ calcd for C54H73N12O10Si2,
19c as an orange glass (0.066 g, 57%). 1H NMR (CDCl3, 300 1105.5106; found, 1105.5086.
MHz) 0.03 (s, 9H), 0.96–1.01 (m, 2H), 1.24–1.27 (m, 11H), 1.58–
Teoc-FA-DA-prod(C4) (24c). Compound 24c was obtained
1.60 (m, 4H), 1.74 (quint., 4H, J ¼ 6.1 Hz), 2.09–2.14 (m, 3H), according to GP2 as a dark red solid (0.098 g, 70%). Mp 124–
2.19 (s, 3H), 2.29 (t, 2H, J ¼ 7.3 Hz), 2.38 (s, 3H), 2.63 (t, 2H, J ¼ 126 ꢁC. 1H NMR (CDCl3, 500 MHz) 0.02 (s, 9H), 0.05 (s, 9H),
7.3 Hz), 3.32 (q, 4H, J ¼ 6.1 Hz), 3.38–3.43 (m, 1H), 3.50–3.64 (m, 0.99–1.05 (m, 4H), 1.21–1.25 (m, 8H), 1.56 (s, 4H), 1.98 (s, 1H),
13H), 3.96 (s, 3H), 4.15–4.21 (m, 2H), 6.04 (s, 1H), 6.19 (dd, 1H, J 2.13–2.17 (m, 3H), 2.26–2.34 (m, 8H), 2.57–2.61 (m, 2H), 3.21
¼ 3.6, 2.7 Hz), 6.24 (br s, 1H), 6.49 (br s, 1H), 6.71 (dd, 1H, J ¼ (br s, 1H), 3.33 (s, 1H), 3.43–3.50 (m, 2H), 3.94 (s, 3H), 4.20–4.29
3.6, 1.1 Hz), 6.74–6.75 (m, 1H), 6.91 (s, 1H). 13C NMR (CDCl3, (m, 4H), 4.58 (s, 2H), 4.65–4.68 (m, 1H), 5.56 (br s, 1H), 5.97 (s,
125 MHz), ꢀ1.4 (3C), 12.4, 14.3, 17.6, 24.3, 25.9, 29.2, 29.3, 29.4, 1H), 6.25 (br s, 1H), 6.59 (br s, 2H), 6.72 (br s, 1H), 6.84 (s, 2H),
29.5, 29.8, 30.5, 32.9, 36.9, 37.8 (ꢂ2), 42.8, 54.1, 58.6, 63.4, 70.0 6.96–6.97 (m, 2H), 7.12 (br s, 1H), 7.19 (br s, 1H), 7.63–7.64 (m,
(ꢂ2), 70.2, 70.6 (4C), 96.0, 110.7, 112.1, 113.7, 123.2, 123.5, 2H), 8.74 (s, 1H). 13C NMR (CDCl3, 125 MHz), ꢀ1.5 (6C), 11.8,
126.3, 128.3, 129.5, 140.8, 142.0, 160.8, 179.0, 172.4, 173.3, 15.3, 16.8, 17.1, 23.8, 25.2, 26.3, 28.2, 28.8, 28.9, 31.7, 35.4, 37.8
175.9, 198.2. HRMS (TOF) (m/z): [M + Na]+ calcd for C46H74N6- (2C), 41.8, 46.1, 52.2, 58.4, 62.4, 63.6, 77.6, 96.2, 110.1, 111.2
Na1O9Si1, 905.5179; found, 905.5145.
(2C), 111.3, 113.0, 121.2, 121.3, 122.4, 122.9, 126.3, 127.4, 128.2,
129.0, 129.6 (2C), 140.6, 142.1, 148.5, 150.7 (ꢂ2), 152.2, 155.2,
155.6, 159.4, 162.0, 166.3, 167.3, 171.5, 172.3, 196.6. HRMS
(TOF) (m/z): [(M + H)]+ calcd for C58H81N12O10Si2, 1161.5732;
General procedure 2 (GP2)
A solution of linker-prodigiosene conjugate (1 eq.) and 23 (1 eq.) found, 1161.5700.
in anhydrous DMSO (0.05 M) was treated with NEt3 (2 eq.). The
Teoc-FA-PEG-prod(C2) (25a). Compound 25a was obtained
resulting reaction mixture was stirred at room temperature for according to GP2 as an orange-brown solid (0.146 g, 91%). Mp
5 h under N2 atmosphere. Water was added to the reaction 114–115 ꢁC. 1H NMR (CDCl3, 500 MHz) 0.01 (s, 9H), 0.06 (s, 9H),
mixture until a precipitate formed, which was isolated via 0.96–1.00 (m, 2H), 1.02–1.06 (m, 2H), 1.20 (t, J ¼ 7.0 Hz, 1H),
microltration, then washed 3 times with water and dried 1.71 (dt, J ¼ 21.5, 6.0 Hz, 4H), 2.10–2.14 (m, 2H), 2.19–2.29 (m,
under vacuum.
2H), 2.33 (s, 6H), 2.49 (t, J ¼ 6.7 Hz, 2H), 2.97 (t, J ¼ 6.7 Hz, 2H),
Teoc-FA-DA-prod(C2) (24a). Compound 24a was obtained 3.23–3.32 (m, 4H), 3.46–3.63 (m, 12H), 3.92 (s, 3H), 4.16–4.19
according to GP2 as an orange solid (0.096 g, 83%). Mp 148– (m, 2H), 4.28 (t, J ¼ 7.7 Hz, 2H), 4.57–4.64 (m, 3H), 5.38 (br s,
150 ꢁC. 1H NMR (DMSO-d6, 500 MHz) 0.02 (s, 9H), 0.07 (s, 9H), 1H), 5.93 (s, 1H), 6.26 (s, 1H), 6.56 (d, J ¼ 7.2 Hz, 2H), 6.71 (s,
0.93–0.96 (m, 2H), 1.02–1.06 (m, 2H), 1.37 (s, 6H), 1.92–2.27 (m, 2H), 6.78 (s, 2H), 6.96 (br s, 1H), 7.39 (d, J ¼ 6.5 Hz, 1H), 7.67 (d,
4H), 2.36 (s, 3H), 2.68 (s, 3H), 2.73 (s, 1H), 2.98–3.00 (m, 4H), J ¼ 7.2 Hz, 2H), 8.74 (br s, 1H). 13C NMR (CDCl3, 125 MHz),
3.88 (s, 3H), 4.10–4.16 (m, 2H), 4.25–4.30 (m, 2H), 4.35 (br s, ꢀ1.41 (6C), 12.5, 15.4, 17.5, 17.7, 27.7, 29.0, 29.2, 30.4 (2C), 32.9,
1H), 4.57 (br s, 2H), 6.17 (s, 1H), 6.25 (s, 1H), 6.67 (br d, 2H, J ¼ 37.6, 37.8, 38.1 (2C), 46.7, 53.1, 58.6, 63.9, 65.6, 65.9 (2C), 69.6,
7.0 Hz), 6.79 (br s, 1H), 6.83 (br s, 1H), 7.11 (br s, 1H), 7.66 (br d, 69.7, 70.0, 70.1, 70.5 (2C), 95.5, 110.8, 111.5, 112.1 (2C), 113.9,
3H, J ¼ 7.2 Hz), 8.16 (br s, 1H), 8.78 (s, 1H), 11.70 (br s, 1H). 13
C
122.5 (ꢂ2), 123.8, 126.5, 127.7, 129.2, 129.8 (2C), 142.6, 149.0,
NMR (DMSO-d6, 125 MHz), ꢀ1.5 (6C), 11.9, 15.4, 16.8, 17.1, 150.4, 151.5, 154.0, 154.7, 167.5, 168.2, 172.7, 173.1, 196.0 (2
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carbons uncounted for). HRMS (TOF) (m/z): [M + H]+ calcd for z): [(M + H + Na)/2]2+ calcd for C54H73N12Na1O10S2Si2, 596.2211;
C
60H85N12O13Si2, 1237.5892; found, 1237.5890.
found, 596.2220.
Teoc-FA-PEG-prod(C4) (25b). Compound 25b was obtained
Teoc-FA-SS-prod(C4) (26b). A solution of 4b (0.128 g, 0.203
according to GP2 as a dark red solid (0.101 g, 89%). Mp 128– mmol) in a mixture of MeOH : CHCl3 (1 : 1, 4 mL) was treated
130 ꢁC. 1H NMR (CDCl3, 500 MHz) 0.03 (s, 9H), 0.07 (s, 9H), with HCl 12 N (1.2 mL, 14.4 mmol) and the reaction mixture was
0.98–1.01 (m, 2H), 1.04–1.07 (m, 2H), 1.61 (br s, 4H), 1.70–1.72 stirred at room temperature for 4 h. The solvent was removed
(m, 2H), 1.75–1.78 (m, 2H), 2.16–2.22 (m, 4H), 2.30–2.39 (m, under reduced pressure to obtain 4b as dark purple solid (0.124
8H), 2.61 (br s, 2H), 3.23–3.36 (m, 4H), 3.50–3.60 (m, 12H), 3.94 g), which was used in the next step without any further puri-
(s, 3H), 3.97–3.99 (br m, 1H), 4.18–4.22 (m, 2H), 4.27–4.31 (m, cation. HRMS (TOF) (m/z): [M + H]+ calcd for C26H36N5O3S2,
2H), 4.57 (br s, 2H), 4.61–4.66 (m, 2H), 5.44 (br s, 1H), 5.95 (s, 530.2254; found, 530.2264. Compound 26b was obtained
1H), 6.27 (s, 1H), 6.58 (d, 2H, J ¼ 7.2 Hz), 6.72–6.74 (m, 2H), 6.81 according to GP2. The crude mixture was puried by column
(s, 1H), 6.90 (br s, 1H), 6.97 (br s, 1H), 7.41 (d, 1H, J ¼ 7 Hz), 7.68 chromatography using Al2O3 type III neutral (CH2Cl2 : MeOH,
(d, 2H, J ¼ 7.2 Hz), 8.74 (br s, 1H). 13C NMR (CDCl3, 125 MHz), 9 : 1) and 26b was obtained as an orange solid (0.176 g, 72%).
ꢀ1.5 (6C), 12.3, 15.1, 17.4, 17.6, 23.7, 25.4, 27.7, 28.5, 29.0, 29.2, Mp 135–137 ꢁC. 1H NMR (CDCl3, 500 MHz) 0.02 (s, 9H), 0.06 (s,
29.7, 32.8, 36.5, 37.5, 37.8, 42.3, 46.7, 53.0, 58.6, 63.8, 65.7, 69.7, 9H), 0.81–0.90 (m, 1H), 0.96–1.06 (m, 4H), 1.58 (br s, 4H), 2.09–
70.0, 70.1, 70.4 (2C), 95.6, 110.8, 111.5, 112.1 (2C), 114.0, 122.5, 2.19 (m, 4H), 2.26 (br m, 3H), 2.31 (s, 3H), 2.34–2.40 (m, 2H),
123.0, 123.6, 126.4, 127.6, 127.9, 129.1, 129.8 (2C), 139.9, 142.2, 2.57 (br s, 2H), 2.69–2.78 (m, 4H), 3.40–3.53 (m, 4H), 3.93 (s,
149.1, 150.3, 151.5, 154.1, 154.6, 159.4, 161.9, 167.5, 168.3, 3H), 4.16–4.32 (m, 4H), 4.58 (d, 2H, J ¼ 4.0 Hz), 4.65–4.72 (m,
172.6, 172.7, 173.2, 197.4. HRMS (TOF) (m/z): [(M + H + Na)/2]2+ 1H), 5.45–5.46 (m, 1H), 5.95 (s, 1H), 6.25–6.27 (m, 1H), 6.56 (d,
calcd for C62H89N12NaO13Si2, 644.3049; found, 644.3030.
2H, J ¼ 8.6 Hz), 6.72 (br s, 1H), 6.80 (s, 1H), 6.89–6.95 (m, 2H),
Teoc-FA-PEG-prod(C8) (25c). Compound 25c was obtained 7.14 (t, 1H, J ¼ 5.6 Hz), 7.32 (d, 1H, J ¼ 6.7 Hz), 7.65 (d, 2H, J ¼
according to GP2. The crude mixture was puried by column 8.6 Hz), 8.75 (s, 1H). 13C NMR (CDCl3, 125 MHz), ꢀ1.4 (6C), 12.4,
chromatography using Al2O3 type III neutral (CH2Cl2 : MeOH, 15.4, 17.5, 17.7, 23.6, 25.3, 27.3, 29.8, 32.9, 36.4, 37.9, 38.1, 38.6,
9 : 1) and 25c was obtained as dark red glass (0.065 g, 47%). 1H 38.8, 42.2, 46.8, 53.0, 58.7, 64.0, 66.0, 95.6, 111.0, 111.6, 112.2
NMR (CDCl3, 500 MHz) 0.01 (s, 9H), 0.05 (s, 9H), 0.82–0.89 (m, (2C), 114.2, 122.5, 123.1, 124.0, 126.5, 127.5, 129.2 (2C), 129.9,
1H), 0.96–1.07 (m, 4H), 1.25 (br s, 8H), 1.57–1.58 (br m, 4H), 139.8, 142.3, 149.2, 149.9, 150.4, 151.8, 154.0, 154.7, 159.3,
1.68–1.77 (m, 4H), 2.09–2.14 (m, 2H), 2.19–2.25 (m, 2H), 2.29– 161.5, 167.7, 168.3, 172.6, 173.2, 173.8, 197.5. HRMS (TOF) (m/
2.33 (m, 2H), 2.36 (s, 6H), 2.61 (t, 2H, J ¼ 7.1 Hz), 3.27–3.34 (m, z): [(M + H + Na)/2]+ calcd for C56H77N12NaO10S2Si2, 610.2376;
4H), 3.47–3.58 (m, 12H), 3.94 (s, 3H), 4.17–4.22 (m, 2H), 4.26– found, 610.2356.
4.31 (m, 2H), 4.62 (br s, 3H), 5.43 (br s, 1H), 5.98 (s, 1H), 6.24
Teoc-FA-SS-prod(C8) (26c). A solution of 4c (0.150 g, 0.22
(br s, 1H), 6.44–6.48 (m, 1H), 6.60 (d, 2H, J ¼ 8.3 Hz), 6.72 (br s, mmol) in a mixture of MeOH : CHCl3 (1 : 1, 4 mL) was treated
1H), 6.81–6.85 (m, 2H), 6.90 (br s, 1H), 7.40 (d, 1H, J ¼ 7.2 Hz), with HCl 12 N (0.036 mL, 0.44 mmol). Aer an additional
7.67 (d, 2H, J ¼ 8.3 Hz), 8.77 (s, 1H). 13C NMR (CDCl3, 125 MHz), 30 min HCl 12 N (0.030 mL, 0.36 mmol) was added and the
ꢀ1.4 (6C), 12.4, 15.2, 17.5, 17.7, 24.3, 25.9, 27.9, 29.0, 29.3 (ꢂ2), reaction mixture stirred for a further 12 hours. The solvent was
29.4, 29.5 (ꢂ2), 29.8 (2C), 32.9, 36.9, 37.7, 38.0 (2C), 42.8, 46.9, removed under reduced pressure to afford 4c as a red glass
53.1, 58.7, 64.0, 66.1 (2C), 69.9, 70.0, 70.1, 70.2, 70.6, 95.7, 110.9, (0.130 g), which was used in the next step without any further
111.9, 112.3 (2C), 114.0, 122.8, 123.5, 126.6, 127.9, 129.2, 130.1 purication. HRMS (TOF) (m/z): [M
(2C), 140.2, 142.2, 149.4, 150.3, 151.8, 154.0, 154.8, 159.6, 161.0, 30H44N5O3S2, 586.2880; found, 586.2856. Compound 26c was
167.3, 168.5, 172.6, 172.7, 173.5, 198.1. HRMS (TOF) (m/z): [M + obtained according to GP2 as a dark red glass (0.086 g, 69%). 1H
H]+ calcd for C66H97N12O13Si2, 1321.6831; found, 1321.6807.
NMR (CDCl3, 500 MHz) 0.00 (s, 9H), 0.04 (s, 9H), 0.96–1.00 (m,
+
H]+ calcd for
C
Teoc-FA-SS-prod(C2) (26a). Compound 26a was obtained 4H), 1.02–1.04 (m, 8H), 1.21–1.24 (m, 4H), 1.53–1.55 (m, 4H),
according to GP2 as an orange-brown solid (0.042 g, 54%). Mp 2.10–2.13 (m, 3H), 2.21 (app br s, 4H), 2.34–2.36 (m, 5H), 2.57–
1
ꢁ
149–151 C. H NMR (CDCl3, 500 MHz) 0.00 (1 s, 9H), 0.04 (s, 2.58 (m, 2H), 2.68–2.69 (m, 2H), 2.72–2.75 (m, 2H), 3.40–3.52
9H), 0.95 (t, J ¼ 8.5 Hz, 2H), 1.01 (t, J ¼ 8.5 Hz, 2H), 1.25 (s, 1H), (m, 4H), 3.92 (m, 3H), 4.17–4.20 (m, 2H), 4.26 (t, J ¼ 8.2 Hz, 2H),
2.16–2.20 (m, 2H), 2.26 (s, 6H), 2.33–2.39 (m, 2H), 2.45 (br s, 4.58 (s, 2H), 4.64–4.68 (m, 1H), 5.59 (br s, 1H), 5.97 (s, 1H), 6.21
2H), 2.61 (br s, 2H), 2.71–2.72 (m, 2H), 2.92 (br s, 2H), 3.42–3.51 (s, 1H), 6.56 (d, J ¼ 7.5 Hz, 2H), 6.70 (s, 2H), 6.83 (s, 2H), 7.25–
(m, 4H), 3.91 (s, 3H), 4.15 (t, J ¼ 8.5 Hz, 2H), 4.24–4.32 (m, 3H), 7.26 (m, 2H), 7.35 (d, J ¼ 6.0 Hz, 1H), 7.62 (d, J ¼ 7.5 Hz, 2H),
4.55 (br s, 2H), 4.65–4.68 (m, 1H), 5.49 (br s, 1H), 5.92 (s, 1H), 8.74 (s, 1H). 13C NMR (CDCl3, 125 MHz), ꢀ1.4 (6C), 12.4, 14.9,
6.23 (s, 1H), 6.53 (d, J ¼ 7.7 Hz, 2H), 6.69 (s, 1H), 6.72 (s, 1H), 17.5, 17.7, 24.3, 25.8, 28.1, 29.1, 29.2, 29.4 (ꢂ2), 32.8, 36.6, 37.9,
6.91 (s, 1H), 7.06 (br s, 1H), 7.36 (br s, 1H), 7.64 (d, J ¼ 7.7 Hz, 38.0, 38.6, 42.8, 46.9, 52.9, 58.7, 64.1, 66.0, 95.7, 110.9, 111.8,
2H), 8.71 (s, 1H). 13C NMR (CDCl3, 125 MHz), ꢀ1.4 (6C), 12.5, 112.2 (2C), 114.0, 122.5, 123.4, 123.8, 126.4, 127.7, 129.2 (2C),
15.6, 17.5, 17.7, 27.5, 28.5, 29.8, 30.3, 32.8 (2C), 38.0 (2C), 38.7, 130.0, 139.9, 142.1, 149.3, 149.8, 150.4, 151.8, 154.1, 154.8,
38.8, 46.8, 53.1, 58.6, 64.0, 65.9, 95.4, 110.9, 111.3, 112.1, 112.2 159.8, 161.3, 167.6, 168.5, 168.6, 172.6, 173.2, 174.0, 198.1 (1
(2C), 114.1, 122.4, 124.0, 126.5 (2C), 127.5, 129.2 (2C), 130.0, carbon atom unaccounted for). HRMS (TOF) (m/z): [(M + H +
142.9, 149.1, 150.4, 151.9, 154.1, 167.6, 168.1, 172.6, 173.2, Na)/2]2+ calcd for C60H85N12Na1O10S2Si2, 638.2689; found,
173.6, 196.0 (3 carbon atoms unaccounted for). HRMS (TOF) (m/ 638.2663.
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uncounted for). HRMS (TOF) (m/z): [(M + H–Na)]+ calcd for
General procedure 3 (GP3)
C
47H55NaN12O8, 915.4271; found, 915.4232.
FA-PEG-prod(C4) (28a). Compound 28a was obtained
A solution of (1 eq.) Teoc-FA-LINKERS-prod. (1 eq.) in anhy-
drous DMSO (0.1 M) was treated with TBAF (1 M solution in
THF, 2 eq.) and AcOH (1.25/0.1 mmol). The resulting reaction
mixture was stirred at room temperature for 18 h under N2
atmosphere. EtOAc was added to the reaction mixture until
a precipitate formed, which was ltered using Milipore® and
washed 3 times with water. The obtained dark red solid was
dissolved in DMSO (0.1 M), treated with NaOH (0.2 M solution
in MeOH) and stirred at room temperature for 10 min. Water
was added and a precipitate was formed. The resulting sodium
salt was isolated via microltration, then washed 3 times with
water and dried under vacuum.
according to GP3 as a black solid (0.010 g, 41%). Mp 185 ꢁC. 1H
NMR (DMSO-d6, 500 MHz) 1.57–1.63 (m, 4H), 1.86–1.93 (m, 1H),
2.01–2.07 (m, 1H), 2.17 (t, 2H, J ¼ 7.5 Hz), 2.35 (s, 3H), 2.40 (t,
2H, J ¼ 6.7 Hz), 2.69 (s, 3H), 2.97 (t, 2H, J ¼ 6.7 Hz), 3.04–3.10
(m, 4H), 3.34–3.50 (m, 12H), 3.87 (s, 3H), 4.24–4.28 (m, 1H), 4.48
(d, 2H, J ¼ 5.5 Hz), 6.19 (s, 1H), 6.24 (s, 1H), 6.64 (d, 2H, J ¼ 8.7
Hz), 6.70 (s, 1H), 6.79 (s, 1H), 6.88–6.90 (m, 2H), 7.13 (s, 1H),
7.64 (d, 2H, J ¼ 8.7 Hz), 7.78–7.81 (m, 2H), 8.12 (d, 1H, J ¼ 7.0
Hz), 8.64 (s, 1H), 11.82 (br s, 1H). 13C NMR (DMSO-d6, 125 MHz)
11.8, 15.4, 26.6, 29.3, 29.4 (2C), 32.0, 35.8, 37.3 (2C), 45.9, 52.3,
58.4, 68.0 (2C), 68.1, 69.5, 69.7 (4C), 96.3, 110.1, 111.2 (2C),
113.1, 121.4, 122.1, 122.9, 126.3, 127.6, 127.9, 128.2, 128.9 (2C),
140.8, 142.1, 148.5, 150.7, 153.8, 159.4, 166.2, 167.4, 171.5,
173.9, 195.3 (3 carbon atoms unaccounted for). HRMS (TOF) (m/
z): [(M ꢀ H–Na)/2]2ꢀ calcd for C49H58NaN12O11, 495.2179;
found, 495.2177.
FA-PEG-prod(C4) (28b). Compound 28b was obtained
according to GP3 as dark red solid (0.065 g, 79%). Mp decomp.
>170 ꢁC. 1H NMR (DMSO-d6, 500 MHz) 1.55–1.64 (m, 8H), 1.89–
1.93 (m, 1H), 2.02–2.10 (m, 3H), 2.15–2.19 (m, 2H), 2.35 (s, 3H),
2.68 (s, 3H), 2.73 (br s, 2H), 3.02–3.10 (m, 4H), 3.36 (dd, 4H, J ¼
12.6, 6.3 Hz), 3.45–3.48 (m, 8H), 3.87 (s, 3H), 4.23–4.30 (m, 1H),
4.48 (d, 2H, J ¼ 5.7 Hz), 6.19 (s, 1H), 6.24 (br s, 1H), 6.64 (d, 2H, J
¼ 8.6 Hz), 6.70 (s, 1H), 6.80 (br s, 1H), 6.88–6.91 (m, 2H), 7.13 (s,
1H), 7.65 (d, 2H, J ¼ 8.6 Hz), 7.73–7.80 (m, 2H), 8.14 (d, 1H, J ¼
7.4 Hz), 8.64 (s, 1H), 11.81 (br s, 1H). 13C NMR (DMSO-d6, 125
MHz) 11.8, 15.33, 23.5, 25.1, 26.7, 29.3, 29.4 (2C), 32.0, 35.5,
35.7, 35.8 (2C), 41.2, 41.6, 45.9, 58.4, 68.0 (2C), 68.1, 69.5, 69.7
(4C), 96.3, 110.2, 111.2 (2C), 113.1, 121.4, 122.3, 122.9, 126.3,
128.2, 128.9 (2C), 140.8, 142.1, 148.5, 148.6, 150.7, 153.8, 159.4,
161.0, 166.2, 167.4, 171.5, 172.0, 173.9, 196.5. HRMS (TOF) (m/
z): [M–Na]ꢀ calcd for C51H63NaN12O11, 1019.4745; found,
1019.4718.
FA-DA-prod(C2) (27a). Compound 27a was obtained accord-
ing to GP3 as dark red solid (0.040 g, 53%). Mp decomp.
>230 ꢁC. 1H NMR (DMSO-d6, 500 MHz, 80 ꢁC) 1.39 (s, 3H), 1.96–
2.22 (m, 7H), 2.68 (s, 3H), 3.00 (s, 4H), 3.90 (s, 3H), 4.32 (br s,
1H), 4.49 (s, 2H), 6.16 (br s, 1H), 6.26 (br s, 1H), 6.67 (br s, 4H),
6.78 (br s, 1H), 7.09 (br s, 1H), 7.64 (br s, 3H), 7.90 (br s, 1H), 8.65
(br s, 1H), 11.61 (br s, 1H). 13C NMR (DMSO-d6, 125 MHz) 11.8,
15.4, 26.8, 28.2, 29.4, 32.0, 36.6, 37.3, 38.4 (2C), 45.9, 52.3, 58.4,
96.3, 110.2, 111.2 (2C), 113.1, 121.4, 122.1, 122.9, 127.6, 127.9,
128.2, 128.9 (2C), 140.9, 142.0, 148.5, 150.7, 153.9, 155.6, 156.3,
159.4, 161.2, 166.3, 167.4, 171.8, 174.0, 195.3 (1 carbon
uncounted for). HRMS (TOF) (m/z): [(M ꢀ H–Na)/2]2ꢀ calcd for
C
41H42NaN12O8, 415.1630; found, 415.1648.
FA-DA-prod(C4) (27b). Compound 27b was obtained
according to GP3 as dark red solid (0.036 g, 68%). Mp decomp.
1
ꢁ
ꢁ
>200 C. H NMR (DMSO-d6, 500 MHz, 60 C) 1.54 (br s, 4H),
1.85–1.95 (m, 2H), 2.08–2.27 (m, 6H), 2.34 (s, 3H), 2.68 (s, 3H),
2.73 (br s, 2H), 3.06 (br s, 4H), 3.87 (s, 3H), 4.23–4.31 (m, 1H),
4.47 (d, 2H, J ¼ 5.6 Hz), 6.19 (s, 1H), 6.24 (br s, 1H), 6.64 (d, 2H, J
¼ 8.6 Hz), 6.69 (s, 1H), 6.78–6.79 (m, 1H), 6.87–6.91 (m, 2H),
6.78 (br s, 1H), 7.13 (br s, 1H), 7.65 (d, 2H, J ¼ 8.4 Hz), 7.79–7.85
(m, 2H), 8.15 (d, 1H, J ¼ 5.4 Hz), 8.63 (s, 1H), 11.81 (br s, 1H). 13
C
NMR (DMSO-d6, 125 MHz) 11.8, 15.3, 23.4, 24.9, 26.6, 28.2, 32.0,
35.5, 38.3, 38.5, 41.6, 45.9, 52.1, 58.4, 96.3, 110.2, 111.2 (2C),
113.1, 121.4, 122.3, 122.9, 126.3, 127.6, 127.9, 128.2, 128.9 (2C),
140.8, 142.1, 148.5, 150.8, 153.8, 156.3, 159.3, 161.0, 161.1,
166.3, 167.4, 171.7, 172.2, 173.9, 196.3. HRMS (TOF) (m/z): [M ꢀ
H–Na/2]2ꢀ calcd for C43H46NaN12O8, 429.1786; found, 429.1796.
FA-DA-prod(C8) (27c). Compound 27c was obtained accord-
ing to GP3 as a black solid (0.025 g, 67%). Mp decomp. >205 ꢁC.
1H NMR (DMSO-d6, 500 MHz) 1.24–1.27 (m, 8H), 1.45–1.48 (m,
2H), 1.55–1.57 (m, 2H), 1.88–1.93 (m, 1H), 2.01–2.09 (m, 3H),
2.15–2.19 (m, 2H), 2.34 (s, 3H), 2.67 (s, 3H), 2.72 (t, 2H, J ¼ 7.0
Hz), 3.00–3.10 (m, 5H), 3.30 (br s, 4H), 3.87 (s, 3H), 4.28–4.30 (m,
1H), 4.48 (d, 2H, J ¼ 5.5 Hz), 6.19 (s, 1H), 6.24 (s, 1H), 6.64 (d,
2H, J ¼ 8.2 Hz), 6.69 (s, 1H), 6.79 (s, 1H), 6.89–6.91 (m, 2H), 7.14
(s, 1H), 7.65 (d, 2H, J ¼ 8.2 Hz), 7.74 (s, 1H), 7.84 (s, 1H), 8.17 (d,
1H, J ¼ 7.5 Hz), 8.64 (s, 1H), 11.43 (s, 1H), 11.81 (s, 1H). 13C NMR
(DMSO-d6, 125 MHz) 11.7, 15.3, 23.7, 25.1, 27.0, 28.2, 28.7 (ꢂ2),
28.9, 32.0, 35.4, 41.8, 45.9, 52.3, 58.4, 77.5, 96.2, 110.1, 111.2
(2C), 113.0, 121.5, 122.4, 122.9, 126.3, 127.5, 127.9, 128.2, 128.8
(2C), 140.7, 142.0, 148.5, 150.7, 154.0, 155.6, 156.2, 159.3, 161.2,
166.1, 167.3, 171.8, 172.3, 173.0, 174.2, 196.6 (1 carbon
FA-PEG-prod(C8) (28c). Compound 28c was obtained
according to GP3 as dark red solid (0.021 g, 38%). Mp decomp.
1
>150 ꢁC. H NMR (DMSO-d6, 500 MHz) 1.25–1.26 (br m, 8H),
1.44–1.50 (m, 2H), 1.53–1.64 (m, 4H), 2.03 (t, 2H, J ¼ 7.1 Hz),
2.14–2.28 (m, 4H), 2.34 (s, 3H), 2.67 (s, 3H), 2.72 (t, 2H, J ¼ 7.1
Hz), 3.06 (dd, 4H, J ¼ 12.9, 6.8 Hz), 3.33–3.39 (m, 4H), 3.43–3.49
(m, 8H), 3.87 (s, 3H), 4.22–4.29 (m, 1H), 4.48 (d, 2H, J ¼ 5.7 Hz),
6.19 (s, 1H), 6.64 (d, 2H, J ¼ 8.3 Hz), 6.69 (s, 1H), 6.78–6.80 (m,
1H), 6.85–6.92 (m, 3H), 7.13 (br s, 1H), 7.64 (d, 2H, J ¼ 8.3 Hz),
7.69–7.72 (m, 1H), 7.77–7.81 (m, 1H), 8.14 (d, 1H, J ¼ 7.0 Hz),
8.64 (s, 1H), 11.43 (br s, 1H), 11.81 (br s, 1H). 13C NMR (DMSO-
d6, 125 MHz) 11.8, 15.3, 23.8, 25.3, 26.7, 28.6, 28.7, 28.8, 29.0,
29.3, 29.4, 32.0, 35.4, 35.7, 35.8, 41.8, 45.9, 52.3, 58.4, 68.0, 68.1,
69.5 (ꢂ2), 69.7 (4C), 96.3, 110.2, 111.2 (2C), 113.1, 121.4, 122.4,
122.9, 126.3, 127.5, 127.9, 128.2, 128.9 (2C), 140.7, 142.1, 148.5,
148.6, 150.7, 153.8, 153.9, 159.4, 166.2, 167.4, 171.5, 172.0,
173.8, 197.7. HRMS (TOF) (m/z): [(M ꢀ H–Na)/2]ꢀ calcd for
C
55H70NaN12O11, 537.2649; found, 537.2664.
FA-SS-prod(C4) (29a). Compound 29a was obtained accord-
1
ing to GP3 as a dark red solid (0.009 g, 26%). H NMR (DMSO-
d6, 300 MHz, 50 ꢁC) 1.86–1.96 (m, 1H), 2.03–2.17 (m, 1H), 2.19–
14090 | RSC Adv., 2019, 9, 14078–14092
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2.23 (m, 2H), 2.35 (s, 3H), 2.42 (t, 2H, J ¼ 6.6 Hz), 2.68 (s, 3H),
2.72–2.96 (m, 4H), 3.00 (t, 1H, J ¼ 7.0 Hz), 3.30–3.36 (m, 5H),
3.89 (s, 3H), 4.29 (br s, 1H), 4.49 (d, 1H, J ¼ 4.5 Hz), 6.20 (s, 1H),
6.25 (s, 1H), 6.62–6.70 (m, 3H), 6.89–6.93 (m, 3H), 7.04–7.07 (m,
1H), 7.13 (s, 1H), 7.65 (d, 2H, J ¼ 7.5 Hz), 8.06 (t, 1H, J ¼ 5.7 Hz),
8.15–8.17 (m, 1H), 8.64 (s, 1H), 11.82 (br s, 1H). 13C NMR
(DMSO-d6, 125 MHz) 11.8, 15.4, 26.5, 28.2, 29.3, 31.9, 37.2 (2C),
37.3, 37.9, 38.1 (2C), 39.0, 45.9, 52.1, 58.4, 96.3, 110.1 (2C),
111.1, 113.1, 121.3, 122.1, 122.9, 126.3, 127.6, 127.9, 128.1, 128.9
(2C), 140.9, 142.0, 148.6, 150.7, 153.8, 159.3, 166.2, 167.3, 171.7
(ꢂ2), 173.8, 195.1 (1 carbon atom unaccounted for). HRMS
(TOF) (m/z): [(M ꢀ H–Na)/2]2ꢀ calcd for C43H46NaN12O8S2,
461.1507; found, 461.1530.
5 Y. Ren, J. Gong, R. Fu, Z. Li, Q. Li, J. Zhang, Z. Yu and
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6 A. Furstner and E. J. Grabowski, ChemBioChem, 2001, 2, 706–
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7 A. Furstner, K. Reinecke, H. Prinz and H. Waldmann,
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2005, 85, 870–879.
FA-SS-prod(C4) (29b). Compound 29b was obtained accord-
ing to GP3 as dark red solid (0.047 g, 30%). Mp decomp.
>210 ꢁC. 1H NMR (DMSO-d6, 500 MHz) 1.55 (br s, 4H), 1.84–1.96 11 S. Ohkuma, T. Sato, M. Okamoto, H. Matsuya, K. Arai,
(m, 2H), 2.02–2.12 (m, 2H), 2.16–2.22 (m, 2H), 2.35 (s, 3H), 2.68
(s, 3H), 2.73–2.78 (m, 6H), 3.29–3.32 (m, 4H), 3.87 (s, 3H), 4.23–
T. Kataoka, K. Nagai and H. H. Wasserman, Biochem. J.,
1998, 334, 731–741.
4.32 (m, 1H), 4.48 (d, 2H, J ¼ 5.5 Hz), 6.19 (s, 1H), 6.24 (br s, 1H), 12 G. Park, J. T. Tomlinson, M. S. Melvin, M. W. Wright,
6.66 (d, 2H, J ¼ 8.6 Hz), 6.80 (br s, 1H), 6.88–6.93 (m, 2H), 6.99 C. S. Day and R. A. Manderville, Org. Lett., 2003, 5, 113–116.
(br s, 1H), 7.13 (br s, 1H), 7.64 (dd, 2H, J ¼ 8.6, 2.8 Hz), 7.96–8.04 13 R. I. Saez Dıaz, S. M. Bennett and A. Thompson,
(m, 2H), 8.09–8.16 (m, 1H), 8.64 (s, 1H), 11.81 (br s, 1H). 13C
ChemMedChem, 2009, 4, 742–745.
NMR (DMSO-d6, 125 MHz) 11.8, 15.3, 23.4, 25.0, 26.6, 32.0, 35.4, 14 T. Sato, H. Konno, Y. Tanaka, T. Kataoka, K. Nagai,
´
´
37.2 (ꢂ2), 37.3, 37.9, 38.0, 41.6, 45.9, 52.3, 58.4, 96.3, 110.2,
H. H. Wasserman and S. Ohkuma, J. Biol. Chem., 1998,
273, 21455–21462.
111.2 (2C), 113.1, 121.4, 122.4, 122.9, 126.3, 127.9, 128.2, 128.9
(2C), 140.8, 142.1, 148.5, 150.7, 153.8, 156.3, 159.3, 161.1, 166.0, 15 J. L. Seganish and J. T. Davis, Chem. Commun., 2005, 5781–
166.2, 166.3, 167.3, 171.8, 172.3, 173.9, 196.5. HRMS (TOF) (m/ 5783.
z): [M–Na]ꢀ calcd for C45H51NaN12O8S2, 951.3400; found, 16 W. R. Hearn, M. K. Elson, R. H. Williams and J. Medina-
951.3369.
Castro, J. Org. Chem., 1970, 35, 142–146.
17 E. Marchal, S. Rastogi, A. Thompson and J. T. Davis, Org.
Biomol. Chem., 2014, 12, 7515–7522.
Conflicts of interest
18 E. Marchal, D. A. Smithen, I. M. Uddin, A. W. Robertson,
D. L. Jakeman, V. Mollard, C. D. Goodman,
K. S. MacDougall, S. A. McFarland, G. I. McFadden and
A. Thompson, Org. Biomol. Chem., 2014, 12, 4132–4142.
19 E. Marchal, M. I. Uddin, D. A. Smithen, L. A. Hawco,
M. Lanteigne, D. P. Overy, R. G. Kerr and A. Thompson,
RSC Adv., 2013, 3, 22967–22971.
There is no conict to declare.
Acknowledgements
During this work, E. M. was supported by a trainee award from
The Beatrice Hunter Cancer Research Institute (BHCRI) with
funds provided by Cancer Care Nova Scotia as part of The Terry 20 S. Rastogi, E. Marchal, I. Uddin, B. Groves, J. Colpitts,
Fox Foundation Strategic Health Research Training Program in
Cancer Research at Canadian Institutes of Health Research
S. A. McFarland, J. T. Davis and A. Thompson, Org. Biomol.
Chem., 2013, 11, 3834–3845.
(CIHR). This work was funded by research grants to A. T. from: 21 J. Regourd, A. Al-Sheikh Ali and A. Thompson, J. Med. Chem.,
CIHR (Grant # 133110), Canadian Breast Cancer Foundation-
2007, 50, 1528–1536.
Atlantic, Breast Cancer Society of Canada/QEII Foundation 22 R. I. Saez Dıaz, J. Regourd, P. V. Santacroce, J. T. Davis,
´
´
Awards for Breast Cancer Research, BHCRI and Nova Scotia
Health Research Foundation. A. T. is a Senior Scientist of the
BHCRI.
D. L. Jakeman and A. Thompson, Chem. Commun., 2007,
2701–2703.
23 D. A. Smithen, A. M. Forrester, D. P. Corkery, G. Dellaire,
J. Colpitts, S. A. McFarland, J. N. Berman and
A. Thompson, Org. Biomol. Chem., 2013, 11, 62–68.
24 M. I. Uddin, S. Thirumalairajan, S. M. Crawford,
T. S. Cameron and A. Thompson, Synlett, 2010, 2561–2564.
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