Chemoenzymatic synthesis, nanotization, and anti-Aspergillus activity of optically enriched fluconazole analogues

Article abstract of DOI:10.1128/AAC.00273-17

Despite recent advances in diagnostic and therapeutic methods in antifungal research, aspergillosis still remains a leading cause of morbidity and mortality. One strategy to address this problem is to enhance the activity spectrum of known antifungals, and we now report the first successful application of Candida antarctica lipase (CAL) for the preparation of optically enriched fluconazole analogues. Anti-Aspergillus activity was observed for an optically enriched derivative, ()-S-2-(2=,4=difluorophenyl)-1-hexyl-amino-3-(1,2,4)triazol-1-yl-propan-2-ol, which exhibits MIC values of 15.6 g/ml and 7.8 g/disc in broth microdilution and disc diffusion assays, respectively. This compound is tolerated by mammalian erythrocytes and cell lines (A549 and U87) at concentrations of up to 1,000 g/ml. When incorporated into dextran nanoparticles, the novel, optically enriched fluconazole analogue exhibited improved antifungal activity against Aspergillus fumigatus (MIC, 1.63 g/ml). These results not only demonstrate the ability of biocatalytic approaches to yield novel, optically enriched fluconazole derivatives but also suggest that enantiomeri-cally pure fluconazole derivatives, and their nanotized counterparts, exhibiting anti-Aspergillus activity may have reduced toxicity.

Full text of DOI:10.1128/AAC.00273-17

AAC Accepted Manuscript Posted Online 12 June 2017
Antimicrob. Agents Chemother. doi:10.1128/AAC.00273-17
Copyright © 2017 Malhotra et al.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.
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Chemoenzymatic synthesis, nanotization and anti-Aspergillus
activity of optically enriched fluconazole analogues
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Shashwat Malhotra,¶,a,b Seema Singh,¶,c Neha Rana,a Shilpi Tomar,a Priyanka Bhatnagar,c
Mohit Gupta,a Suraj K. Singh,a Brajendra K. Singh,a Anil K. Chhillar,d Ashok K. Prasad,a
Christophe Len,e Pradeep Kumar,c Kailash C. Gupta,c Anjani J. Varma,f Ramesh C. Kuhad,f
Gainda L. Sharma,c,* Virinder S. Parmara,f,g,* and Nigel G. J. Richardsh,*
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aBioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi – 110 007, India;
bKirori Mal College, Department of Chemistry, University of Delhi, Delhi – 110 007, India;
cCSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi – 110 007, India;
dCentre for Biotechnology, Maharishi Dayanand University, Rohtak, Haryana, India;
eSorbonne Universités, Université de Technologie de Compiègne, EcoleSupérieure de
Chimie Organique et Minérale, France;
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fSchool of Chemical Sciences, Central University of Haryana, Mahendragarh, Haryana – 123
031, India;
gInstitute of Advanced Sciences, 86-410 Faunce Corner Mall Road, Dartmouth, MA 02747,
USA;
hSchool of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT, UK
¶Authors contributed equally to this work
Address correspondence to Gainda Sharma, drglsharma@hotmail.com; Virinder Parmar,
virparmar@gmail.com; Nigel G. J. Richards, RichardsN14@cardiff.ac.uk
Running title: Chemoenzymatic synthesis of optically enriched fluconazole
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analogues.
Keywords: chemoenzymatic synthesis, fluconazole, antifungal agents

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Despite recent advances in diagnostic and therapeutic advances in antifungal
research, aspergillosis still remains a leading cause of morbidity and mortality. One
strategy to address this problem is to enhance the activity spectrum of known
antifungals, and we now report the first successful application of Candida antarctica
lipase (CAL) for the preparation of optically enriched fluconazole analogs. Anti-
Aspergillus activity was observed for an optically enriched derivative, (-)-S-2-(2',4'-
difluorophenyl)-1-hexyl-amino-3-(1''',2''',4''') triazol-1'''-yl-propan-2-ol, which exhibits
MIC values of 15.6 µg/mL and 7.8 µg/disc in microbroth dilution and disc diffusion
assays, respectively. This compound is tolerated by mammalian erythrocytes and
cell lines (A549 and U87) at concentrations of up to 1000 µg/mL. When incorporated
into dextran nanoparticles, the novel, optically enriched fluconazole analog exhibited
improved antifungal activity against Aspergillus fumigatus (MIC = 1.63 µg/mL).
These results not only demonstrate the ability of biocatalytic approaches to yield
novel, optically enriched fluconazole derivatives but also suggest that
enantiomerically pure fluconazole derivatives, and their nanotised counterparts,
exhibiting anti-Aspergillus activity may have reduced toxicity.

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Aspergillosis remains a significant threat to public health, and, in spite of
continuous efforts to improve timely diagnosis and clinical therapies, mortality
caused by this disease remains unacceptably high [1, 2]. Current therapeutic
options for treating Aspergillus-induced disorders include antifungal agents
such as polyenes, azoles and echinocandins [3, 4]. Thus the discovery of new
antifungal compounds remains important given the need to address the
development of drug resistance in pathogenic fungi [5-7]. One approach to
accomplishing this goal is to prepare new derivatives of existing drugs with
broad spectrum activity and enhanced pharmacokinetic properties. As part of
our on-going efforts to use lipases [8-12], which catalyze reactions with high
degree of chemo-, regio- and stereoselectivity in organic synthesis, we
became interested in preparing new antifungals using biocatalysis.
Fluconazole, introduced in 1990, is a bis-triazole antifungal drug which
possesses interesting pharmacokinetic properties, such as low plasma binding
affinity, good water solubility, low first pass metabolism, high oral
bioavailability and a long half-life, all of which should make it a drug of choice
for treating fungal infections [13, 14]. On the other hand, fluconazole has been
reported to exhibit only limited activity against Aspergillus infections [15],
which has led to many reports concerning the synthesis of various types of
fluconazole derivatives and their chiral separation/resolution into constituent
enantiomers [16-19]. We now report the use of Candida antarctica lipase
(CAL-B) in catalysing the addition of amines to an achiral epoxide to yield
optically enriched fluconazole analogues in which one of the triazole rings is
replaced by n-alkylamino and cycloalkylamino substituents. To the best of our
knowledge, the work reported herein is the first direct synthesis of optically

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enriched fluconazole analogues using biocatalytic methods. In vitro assays
show that the optically enriched analogues exhibit more potent antifungal
activity than the corresponding racemic mixtures. Interestingly, this bioactivity
can be enhanced by their encapsulation in dextran-based nanoparticles [20].
Results
Synthesis of fluconazole analogues. A series of linear and cyclic alkylamines
was screened for reaction with the epoxide ring of (±)-1-[2-(2, 4-difluorophenyl)-
oxiranylmethyl]-1H-[1,2,4]-triazole (1, Figure 1) in a number of different organic
solvents. Three different immobilized lipases were also evaluated for their ability to
catalyze this reaction: Candida rugosa lipase (CRL), porcine pancreatic lipase (PPL)
and CAL-B. Although the ring-opening reactions catalysed by CRL and PPL were of
no practical utility, when the reaction was performed in the presence of CAL-B in
tetrahydrofuran (THF) as solvent, the desired products (3a-j, 5a and 5b) were
obtained with good yields in optically enriched forms (Figure 1, and Tables S1 and
S2 in Supporting Information). Very importantly, all of the twelve novel fluconazole
analogues formed in the lipase-catalyzed reactions were optically active showing
that aminolysis of the racemic starting epoxide (±)-1 had proceeded in an
enantioselective fashion (Table S1). These twelve compounds could also be
prepared in racemic form, as viscous oils in 75-80 % yields, by direct reaction of the
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alkylamines with the racemic epoxide precursor (±)-1 in THF at 55 C. The time
taken for complete consumption of aliphatic amines 2a-j, 4a and 4b in the CAL-B
catalyzed reaction varied between 18h and 28h, which was considerably shorter
than the 48-56 h required for the chemical addition of the amines (Table S2 in
Supporting Information). The structures of all twelve fluconazole analogues were

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unambiguously established on the basis of spectroscopic data (IR, 1H- and 13C NMR,
and mass spectra), and by comparison to literature data for known compounds 3b,
3c, 5a and 5b [21, 22].
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Although the enantiomeric enrichment of the fluconazole analogues prepared
by lipase-catalyzed addition was not established, we were able to assign the
absolute configuration of the major enantiomer using the optical activity of the
unreacted epoxide isolated from the reaction mixture. These samples rotated
polarized light in a positive (+) direction, meaning that the recovered, unreacted
epoxide was enriched in the enantiomer for which the stereogenic centre has the (S)
configuration (Table S1 in Supporting Information) [23]. CAL-B therefore
preferentially employs (-)-R-1 in the aminolysis reaction and, assuming a standard
SN2 mechanism for reaction of the amine with the epoxide, we can deduce that the
fluconazole analogues must be enriched in the (-)-S-enantiomer (Figure 1).
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Antifungal activities of the fluconazole analogs Pathogenic Aspergillus
strains (Aspergillus fumigatus ITCC 6604, Aspergillus flavus ITCC 5192, and
Aspergillus niger ITCC 0004) were used to determine the in vitro antifungal efficacy
of the fluconazole analogues, in both their optically enriched and racemic forms.
These experiments used standard microbroth dilution (MDA), disc diffusion (DDA)
and spore germination inhibition (PSGI) assays [24, 25]. We note that the MDA
assay is based on the same basic principle as that used in the CLSI micro-dilution
protocol. The only difference between the two assays is that CLSI uses RPMI
medium to prepare diluted drug solutions rather than the Sabouraud dextrose broth
(a medium used to culture Aspergillii in the laboratory) used by us to determine the
MIC of the fluconazole derivatives. As recommended in CLSI protocols, we carefully

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monitored MDA parameters with respect to preparation of the test compounds,
medium preparation, temperature, inoculum size, incubation time, minimum
inhibitory concentration (MIC)/endpoint determination, data recording and
interpretation of results to ensure the validity and quality of our results. On this point,
we note that a previous study from our laboratory [26] showed that results with RPMI
1640 or RPMI 1640 containing glucose were not different from those obtained by
using Sabouraud dextrose broth.
On the basis of their MIC values, all the compounds exhibited moderate to
good anti-Aspergillus activities, with the analogue (-)-S-3d being more potent than
the commercially available fluconazole (Table 1). We also observed that optically
enriched mixtures of (-)-S-3a, (-)-S-3c, (-)-S-3d, (-)-S-3e and (-)-S-5b were more
active than the corresponding racemates. These data also confirm that introducing a
linear aliphatic alkyl side chain is important for imparting antifungal activity, as
reported previously [23, 24]. On the other hand, when additional, “distal” N-
substituted alkyl groups were present, as in compounds (-)-S-3g and (-)-S-3h,
antifungal activity was completely lost (Table 1). Compounds 3j and 5a exhibited no
biological activity in microbroth dilution assays and were not studied further. Our
work also shows that the length of the alkyl side chain is an important factor in
determining activity, i.e. the compound (-)-S-3d, containing an n-hexyl moiety, has
higher activity than (-)-S-3a, (-)-S-3b and (-)-S-3c, which contain ethyl, n-propyl and
n-butyl groups, respectively (Table 1). Decreasing the linker chain length also led to
higher activity. Optically enriched (-)-S-3d was the most potent compound against
Aspergillus fumigatus (Table 1) and was therefore used to examine how
encapsulation in dextran nanoparticles might impact anti-fungal activity.

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Characterization of (-)-S-3d release from O-alkylated dextran
nanoparticles. Dextran nanoparticle-based drug delivery systems are
biocompatible, biodegradable, possess low immunogenicity [20], and can be used
for controlled release of pharmacologically active substances [27]. We therefore
encapsulated optically enriched (-)-S-3d into three types of dextran nanoparticles,
derivatized with O-hexadecyl, O-decyl and O-heptyl chains to ensure amphiphilicity,
and examined their effect on anti-Aspergillus activity. After trapping (-)-S-3d within
each of the nanoparticles by self-assembly (encapsulation efficiencies for the O-
hexadecyl, O-decyl and O-heptyl nanoparticles were 50 ± 4 %, 22 ± 2 % and 30 ± 2
%), the resulting particle size distributions were determined using dynamic light
scattering (DSL). These measurements showed that the sizes of the O-hexadecyl-,
O-decyl- and O-heptyl- derivatized nanoparticles were 140 ± 16 nm, 187 ± 13.16 nm
and 183 ± 14.73 nm, respectively, and that all of the samples had a low
polydispersity index (< 0.3) (Supporting Information). Examination of the rate at
which the fluconazole analogue (-)-(S)-3d was released from each of the three types
of nanoparticles, showed an initial burst for the O-hexadecyl- and O-decyl-
derivatized nanoparticles (Figure 2).
Anti-Aspergillus activity and cytotoxicity of (-)-S-3d encapsulated in O-
alkylated dextran nanoparticles. We next examined the effect of nanoparticle
encapsulation on the activity of (-)-S-3d against Aspergillus fumigatus using a
microbroth dilution assay (Figure 3). After 48 h of incubation (approximately 80 %
release), (-)-S-3d encapsulated in O-decyl-derivatized nanoparticles inhibited the
growth of Aspergillus fumigatus at an effective concentration of 3.16 µg/mL. Perhaps
more importantly, when the optically enriched fluconazole analogue was

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encapsulated in O-hexadecyl nanoparticles, complete inhibition of Aspergillus
fumigatus growth was achieved at an effective concentration of 1.63 µg/mL (41.3 %
release at an initial concentration of 3.95 µg/mL). In addition, nanoparticle-
encapsulated (-)-S-3d exhibits activity at a lower concentration when compared to
both fluconazole and free (-)-S-3d. Although we believe that this effect is associated
with sustained release of the compound over time, it is also possible that drug
uptake is more efficient because the drug in its encapsulated form is more efficiently
captured by the cells. The general importance of this observation is also evident from
the fact that the MIC of amphotericin B was decreased from 1.95 µg/mL to 0.97
µg/mL when the drug was encapsulated in O-heptyl nanoparticles.
The cytotoxicity of (-)-S-3d and amphotericin B when encapsulated in
derivatized nanoparticles was also evaluated using haemolysis and MTT-based
assays (Figure 4). Perhaps unsurprisingly, given that erythrocytes and cell lines
treated with empty dextran nanoparticles (> 90 % cell viability at concentrations of 2
mg/mL) remained completely viable up to 1 mg/mL, the encapsulated, optically
enriched fluconazole analogue (-)-S-3d exhibited similar cytotoxicity to that of the
free compound. Thus, essentially no toxicity to two human cell lines (Figures 4b and
4c) was seen when the compound was present at concentrations similar to the MIC
values observed for its anti-fungal activity. The optically enriched fluconazole
analogue (-)-S-3d was also considerably less cytotoxic than free amphotericin B in
all assays (Figure 4). It is therefore interesting to note that encapsulating
amphotericin B into O-hexadecyl derivatized nanoparticles lowered the cytotoxicity of
this antifungal agent in both the hemolysis and MTT-based assays. Nevertheless,
cell viability was reduced for amphotericin B-containing nanoparticles relative to
derivatized nanoparticles containing fluconazole analogue (-)-S-3d.

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Conclusions
Reacting alkylamines with a racemic epoxide precursor (Figure 1) in the
presence of immobilized lipase CAL-B in THF provides a simple approach for
the preparation of optically enriched fluconazole analogs, which appear to
exhibit better antifungal activity against Aspergillus than fluconazole. Although
the extent to which the enzyme catalyzes the coupling reaction in an
enantioselective manner remains to be determined, we have been able to
assign the (S)-configuration to the stereogenic centre of the enantiomer that
exhibits biological activity, assuming that (i) the aminolysis reaction proceeds
with its usual chemical mechanism, and (ii) only one enantiomer has antifungal
activity. Given the difficulty of single-step chemical strategies for the
preparation of chiral fluconazoles in optically enriched form, we anticipate that
the enzymatic methodology reported herein will have significant impact in this
approach to obtaining novel variants of existing antifungal drugs.
The most active analogue prepared in this study, (-)-S-3d, is more
potent against Aspergillus fumigatus than fluconazole, having MIC values of 8-
16 µg/mL in a series of in vitro assays. Perhaps more importantly for drug
discovery, the anti-Aspergillus potency of this compound is enhanced (MIC
1.6-4.0 µg/mL) by encapsulation in derivatized nanoparticles, with minimal in
vitro cytotoxic effects at concentrations of up to 2 mg/mL against human
erythrocytes and cell lines of human origin.
Materials and Methods
General procedure for the CAL-B catalysed synthesis of optically
enriched fluconazole analogues. CAL-B immobilized on accurel beads (300

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mg) was added to a solution of the epoxide (±)-1 (5.0 mmol) and the appropriate
amine (2a-j, 4a or 4b, 2.5 mmol) dissolved in THF, and the mixture incubated at 55
°C. The extent of the reaction was monitored by TLC and the enzyme was removed
by filtration when the amine was consumed. After removal of THF at reduced
pressure, the residue was subjected to column chromatography using chloroform/
methanol as eluent to afford optically enriched samples of pure fluconazole
analogues (-)-S-3a-3j, (-)-S-5a or (-)-S-5b and the unreacted epoxide (+)-S-1.
(-)-S-2-(2',4'-Difluorophenyl)-1-hexylamino-3-(1''',2''',4''')triazol-1'''-yl-prop-
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D
an-2-ol (3d) was obtained as a viscous oil in 80% yield. [α]
-20.3 (c 0.01,
CHCl3); IR spectrum (film) µmax: 3315 (OH and NH), 2979, 1620, 1508, 1415, 1267,
1
1145, 960 cm-1. H NMR (400 MHz, CDCl3): δ 0.83 (3H, t, J = 7.63 Hz), 1.17-1.33
(8H, m), 2.43 (2H, t, J = 6.87 Hz), 2.81 (1H, d, J = 12.97 Hz), 3.12 (1H, d, J = 12.21
Hz), 4.49 (1H, d, J = 14.50 Hz), 4.58 (1H, d, J = 13.73 Hz), 6.74-6.82 (2H, m), 7.50-
7.55 (1H, m), 7.77 (1H, s) and 8.10 (1H, s). 13C NMR (100 MHz, CDCl3): δ 13.92,
22.46, 26.55, 29.83, 31.49, 50.00, 54.14 (d, JCF= 3.83 Hz), 55.98 (d, JCF= 4.79 Hz),
72.96 (d, JCF= 5.75 Hz), 104.12 (d, JCF=26.84 Hz), 111.38 (d, JCF= 20.61 Hz), 125.05
(d, JCF = 13.42 Hz), 129.79 (d, JCF = 6.71 Hz), 144.60, 151.09, 158.92 (d, JCF
=
237.78 Hz) and 162.29 (d, JCF = 249.20 Hz). HRMS: m/z 339.1991 ([M+H]+,
C17H25F2N4O calcd. 339.1969).
Microbroth dilution assay Various concentrations of different derivatives in the
range of 0.24-1000.0 µg/mL were prepared in 96 well culture plates (Nunc, Roskilde,
Denmark) by serial dilution in Sabouraud dextrose broth. Wells were inoculated with
1 x 106 spores (conidia) of Aspergillus in 10 µL of spore suspension. Negative

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controls were solvent in medium and spores only, with amphotericin B and
fluconazole being used as positive controls. Plates were incubated at 37 ºC using a
BOD incubator (Calton, NSW, India) and examined macroscopically after 48 h for the
growth of Aspergillus mycelia. The activity of the analogues was defined as positive
if the medium appeared clear without any growth of Aspergillus mycelia, and the
minimum concentration of compounds inhibiting growth was reported as MIC (Table
1).
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Disc diffusion assay Autoclaved Sabouraud dextrose agar (SDA) was poured into
radiation-sterilized petri dishes (10.0 cm diameter). A suspension of conidia of
Aspergillus was prepared and overlaid on the agar plates. Different concentrations of
the fluconazole analogues were impregnated on 5.0 mm diameter sterilized discs
(Whatman No. 1) and placed on the agar. Control discs containing solvent,
amphotericin B or fluconazole were also included in the assay. Plates were
incubated at 37 ºC and the zone of inhibition determined after 72 h. MICs reported
for this assay (Table 1) correspond to fluconazole analogue concentrations giving a
zone of inhibition of at least 6.0 mm diameter from the centre of the plate.
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Percent spore germination inhibition assay Serial dilutions, ranging from 0.24-
1000.0 µg/mL, of each fluconazole analogue dissolved in Sabouraud dextrose broth
were placed in radiation-sterilized petri dishes (10.0 cm diameter), with each dish
then being inoculated with 100 ± 5 Aspergillus conidia. After incubation for 16 h at 37
ºC, wells were examined for spore germination using an inverted microscope (Nikon
Diphot, Japan), and the number of germinated, and non-germinated, spores

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recorded. MICs in this assay (Table 1) correspond to fluconazole analog
concentrations resulting in inhibition of spore germination.
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In vitro cytotoxicity assays. Two approaches were performed to assess the
cytotoxicity of the fluconazole analogues. First, using a standard haemolytic assay
[28], erythrocytes from healthy individuals were suspended in phosphate buffered
saline (PBS) to give a 2 % suspension (v/v). These cells were then incubated with
various concentrations of each compound for 1 h at 37 °C before being pelleted by
centrifugation at 3000 x g for 10 min. The percentage haemolysis was then
calculated from the optical density at 450 nm of the supernatant (Figure 4a). The
effect of solvent and PBS on erythrocyte viability was also checked. Triton X-100
(Sigma Chemicals, USA) was used for complete haemolysis of the erythrocytes.
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In an alternate approach, an MTT-based assay [29] was used to examine the
cytotoxicity of the analogues against A549 (human pulmonary epithelial cells)
and U87 (primary glioblastoma cells) human cell lines, obtained from National
Centre for Cell Science, Pune, India (Figures 4b and 4c). Briefly, cells were
cultured in RPMI-1640 medium supplemented with L-glutamine and fetal calf
serum (10 % v/v), before being harvested at the log phase of confluency and
re-suspended in RPMI-1640 medium. Samples (2 x 104 cells in 100 µL) were
seeded into culture plates and allowed to grow overnight at 37 °C under 5 %
(v/v) CO2. Fluconazole analogues were added at a variety of concentrations
and the cells were incubated under the same conditions for 24 h. Equivalent
amounts of solvent, amphotericin B and fluconazole were used as negative
and positive controls. The medium was removed from each well before the
addition of 50.0 µg of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium

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bromide (MTT) in PBS (100 µL). After incubation for a further period of 4 h at
37 °C, the MTT solution was removed and the cells were lysed using
isopropanol-HCl (100.0 µL). The absorption of each well (at 540 nm) was used
to determine the percentage cytotoxicity in a micro-plate reader (Spectra max
384 plus, Molecular Devices, USA).
Acknowledgements
The Council of Scientific and Industrial Research (CSIR, New Delhi), the
University of Delhi and the University Grants Commission (UGC, New Delhi)
provided research facilities and funding for this study. SM acknowledges the
financial support from CSIR, New Delhi through the award of a Senior
Research Associateship.
References
1. Rousseau N, Picot S, Bienvenu AL. 2014. Erythropoietin combined with
liposomal Amphotericin B improves outcome during disseminated aspergillosis in
mice. Front Immunol 5:1-4.
310
311
312
2. Arvanitis M, Ziakas PD, Zacharioudakis IM, Zervou FN, Caliendo AM,
Mylonakis E. 2014. PCR in diagnosis of invasive aspergillosis: a meta-
analysis of diagnostic performance. J Clin Microbiol 52:3731-3742.
313
314
315
3. Roemer T, Krysan DJ. 2014. Antifungal drug development: challenges,
unmet clinical needs, and new approaches. Cold Spring Harb Perspect Med
4:1-14.
316
317
4. McCormick A, Jacobsen ID, Broniszewska M, Beck J, Heesemann J,
Ebel F. 2012. The two-component sensor kinase TcsC and its role in stress

318
319
resistance of the human-pathogenic mold Aspergillus fumigatus. PLoS One
7:e38262.
320
321
322
5. Yu S, Wang N, Chai X, Wang B, Cui H, Zhao Q, Zou Y, Sun Q, Meng
Q, Wu Q. 2013. Synthesis and antifungal activity of novel triazole analogues
containing 1,2,3-triazole fragment. Arch Pharm Res 36:1215-1222.
323
324
325
6. Singh S, Dabur R, Gatne MM, Singh B, Gupta S, Pawar S, Sharma
SK, Sharma GL. 2014. In vivo efficacy of a synthetic coumarin derivative in a
murine model of aspergillosis. PLoS One 9:1-7.
326
327
7. Sanglard D. 2016. Emerging threats in antifungal-resistant fungal pathogens.
Front Med doi:10.3389/fmed.2016.00011.
328
329
330
331
332
333
8. Kumar A, Khan A, Malhotra S, Mosurkal R, Dhawan A, Pandey MK,
Singh BK, Kumar R, Prasad AK, Sharma SK, Samuelson LA, Cholli AL,
Len C, Richards NGJ, Kumar J, Haag R, Watterson AC, Parmar VS. 2016.
Synthesis of macromolecular systems via lipase catalyzed biocatalytic
reactions: Applications and future perspectives. Chem Soc Rev 45:6855-
6887.
334
335
9. Gandhi NN, Patil NS, Sawant SB, Joshi JB, Wangikar PP, Mukesh D.
2000. Lipase-catalyzed esterification. Catal Rev 42:439-480.
336
337
338
339
10.Kumar R, Chen MH, Parmar VS, Samuelson LA, Kumar J, Nicolosi
R, Yoganathan S, Watterson AC. 2004.Supramolecular assemblies based
on copolymers of PEG 600 and functionalized aromatic diesters for drug
delivery applications. J Am Chem Soc 126:10640-10644.

340
341
342
11.Malhotra S, Calderón M, Prasad AK, Parmar VS, Haag R. 2010. Novel
chemoenzymatic methodology for the regioselective glycine loading on
polyhydroxy compounds. Org Biomol Chem 8:2228-2237.
343
344
345
12.Bhatia S, Mohr A, Mathur D, Parmar VS, Haag R, Prasad AK. 2011.
Biocatalytic route to sugar-PEG-based polymers for drug delivery
applications. Biomacromolecules 12:2543-2555.
346
347
348
349
13.Tett S, Moore S, Ray J. 1995. Pharmacokinetics and bioavailability of
fluconazole in two groups of males with human immunodeficiency virus (HIV)
infection compared with those in a group of males without HIV infection.
Antimicrob Agents Chemother 39:1835-1841.
350
351
14.Lass-Flörl C. 2011. Triazole antifungal agents in invasive fungal infections: A
comparative review. Drugs 71:2405-2419.
352
353
354
15.Karthaus M. 2011. Prophylaxis and treatment of invasive aspergillosis with
voriconazole, posaconazole and caspofungin - review of the literature. Eur J
Med Res 16:145-152.
355
356
357
16.Yamada H, Tsuda T, Watanabe T, Ohashi M, Murakami K, Mochizuki H.
1993. In vitro and in vivo antifungal activities of D0870, a new triazole agent.
Antimicrob Agents Chemother 37:2412-2417.
358
359
360
17.Young-Min N. 2011. Synthesis and activity of novel 1-halogenobenzylindole
linked triazole analogues as antifungal agents. Bull Korean Chem Soc
32:307-310.
361
362
363
18.Pore VS, Jagtap MA, Agalave SG, Pandey AK, Siddiqi MI, Kumar V,
Shukla PK. 2012. Synthesis and antifungal activity of 1, 5-disubstituted-1, 2,
3-triazole containing fluconazole analogues. MedChemCommun 3:484-488.

364
365
366
367
19.Borate HB, Sawargave SP, Chavan SP, Chandavarkar MA, Iyer RR,
Nawathye VV, Chavan GJ, Tawte AC, Rao DD. 2012. Enantiomers of
fluconazole analogues containing thieno-[2,3-d]pyrimidin-4(3h)-one moiety as
antifungal agents. PCT Int Appl: WO 2012123952 A1.
368
369
370
20.Yang J, Han S, Zheng H, Dong H, Liu J. 2015. Preparation and application
of micro/nanoparticles based on natural polysaccharides. Carbohydr Polym
123:53-66.
371
372
373
374
21.Chai X, Zhang J, Yu S, Hu H, Zou Y, Zhao Q, Dan Z, Zhang D, Wu Q
.
2009. Design, synthesis and biological evaluation of novel 1-(1H-1,2,4-
triazole-1-yl)-2-(2,4-difluorophenyl)-3-substituted
benzylamino-2-propanols.
Bioorg Med Chem Lett 19:1811-14.
375
376
377
378
22.Zhao Q, Song Y, Hu H, Sun Q, Zhang J, Wu Q. 2006. Synthesis of α-(2,4-
difluorophenyl)-α-(1H-1,2,4-triazol-1-ylmethyl)-1-piperidineethanol analogues
and determination of their activity as antifungal agents. Zhongguo Yaowu
Huaxue Zazhi 16:150-153.
379
380
381
382
383
23.Saksena AK, Girijavallabhan VM, Lovey RG, Pike RE, Desai JA, Ganguly
AK, Hare RS, Loebenberg D, Cacciapuoti A, Parmegiani RM. 1994.
Enantioselective synthesis of the optical isomers of broad-spectrum orally
active antifungal azoles, Sch 42538 and Sch 45012. Bioorg Med Chem Lett
4:2023-2028.
384
385
24.Dabur R, Sharma GL. 2002. Studies on antimycotic properties of
Daturametel. J Ethnopharmacol 80:193-197.

386
387
388
25.Yadav V, Mandhan R, Dabur R, Chhillar AK, Gupta J, Sharma GL. 2005.
A fraction from Escherichia coli with anti-Aspergillus properties. J Med
Microbiol 54:375-379.
389
390
391
26.Dabur R, Chhillar AK, Yadav V, Kamal PK, Gupta J, Sharma GL. 2005. In
vitro antifungal activity of 2-(3,4-dimethyl-2,5-dihydro-1H-pyrrol-2-yl)-1-
methylethyl pentanoate, a dihydropyrrole derivative. J Med Microbiol 54:1-4.
392
393
394
27.Yoo JW, Doshi N, Mitragotri S. 2011. Adaptive micro and nanoparticles:
temporal control over carrier properties to facilitate drug delivery.
Adv Drug Deliv Rev 63:1247-1256.
395
396
397
28.Latoud C, Peypoux F, Michel G, Genet R, Morgat JL. 1986. Interactions of
antibiotics of the iturin group with human erythrocytes. Biochim Biophys Acta
856: 526-535.
398
399
400
29.Mossman T. 1983. Rapid colorimetric assay for cellular growth and survival:
application to proliferation and cytotoxicity assays. J Immunol Methods 65:
55-63.

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Figure Captions
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Figure 1. CAL-B catalyzed epoxide ring opening with open chain and cyclic aliphatic
amines. Note that samples of each compound could also be prepared in racemic
form by heating the epoxide and amine at 55 oC in THF (see Supporting
Information). The new stereogenic centre is indicated by an asterisk.
Figure 2. In vitro release of (-)-S-3d from O-hexadecyl- (blue triangles), O-decyl-
(red circles) and O-heptyl-derivatized (grey squares) dextran nanoparticles.
Figure 3. In vitro antifungal activity of (-)-S-3d, amphotericin B and their
dextran NPs. Lane a: Negative control; Lane b: Empty O-alkyl dextran
nanoparticles; Lane c: Amphotericin B; Lane d: Fluconazole; Lane e: (-)-S-3d
Lane f: O-heptyl nanoparticles containing (-)-S-3d; Lane g: O-decyl
nanoparticles containing (-)-S-3d Lane h: O-hexadecyl nanoparticles
;
;
containing (-)-S-3d; Lanei: O-heptyl nanoparticles containing Amphotericin B;
Lane j: O-decyl nanoparticles containing Amphotericin B; Lane k: O-hexadecyl
nanoparticles containing Amphotericin B.
Figure 4. In vitro cytotoxicity assays for optically enriched (-)-S-3d and amphotericin
B in both the free form and when encapsulated into dextran nanoparticles. (a)
Haemolytic assay; MTT-based assay using (b) A459 and (c) U87 cell lines.

Table 1: In vitro activity of selected, optically enriched fluconazole analogues against Aspergillus species.a,b
Aspergillus fumigatus
Aspergillus niger
Aspergillus flavus
Analogue
MDA
DDA
PSGI
MDA
DDA
PSGI
MDA
DDA
PSGI
(µg/ml)
(µg/disc)
(µg/ml) (µg/ml)
(µg/disc)
(µg/ml) (µg/ml)
(µg/disc)
(µg/ml)
125.0
62.50
125.0
250.0
125.0
250.0
250.0
-
125.0
-
250.0
-
(-)-S-3a
(-)-S-3b
(250.0)
(125.0)
(250.0) (250.0)
(125.0)
(250.0)
250.0
62.50
250.0
500.0
-
125.0
-
500.0
-
-
-
-
-
-
-
(250.0)
(125.0)
(250.0)
62.50
31.25
62.50
62.50
31.25
62.50
500.0
125.0
500.0
(-)-S-3c
(125.0)
(31.25)
(125.0) (500.0)
(125.0)
(500.0) (1000.0)
(125.0)
(1000.0)
15.62
7.81
15.62
62.50
15.62
62.50
125.0
15.62
125.0
(-)-S-3d
(-)-S-3e
(-)-S-3i
(15.62)
(7.81)
(15.62) (125.0)
(31.25)
(125.0) (125.0)
(31.25)
(125.0)
62.50
31.25
62.50
125.0
62.50
125.0
500.0
125.0
-
500.0
(125.0)
(62.50)
(125.0) (500.0)
(125.0)
(500.0) (500.0)
(500.0)
500.0
250.0
500.0
500.0
-
125.0
-
500.0
-
500.0
-
250.0
-
500.0
-
(500.0)
(250.0)
(500.0)

62.50
31.25
62.50
125.0
62.50
125.0
500.0
125.0
500.0
(-)-S-5b
(125.0)
(62.50)
(125.0) (500.0)
(125.0)
(500.0) (500.0)
(125.0)
(500.0)
250.0
1.95
125.0
0.97
250.0
1.95
250.0
1.95
125.0
0.97
250.0
1.95
250.0
1.95
125.0
0.97
250.0
1.95
Fluconazole
Amphotericin B
aValues in parentheses are for the racemic form of the compound.
b(-) shows no activity within the range of concentrations tested.