T.A. Ribeiro et al.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 626 (2021) 126984
refers to an alternative class of cytotoxic compounds that combines the
reactive attributes of the nitro group [40,47] with their specific
amphiphilic nature, also reiterating the functionality of GBL moiety in
biologically active molecules. Amphiphilic properties improve the
permeation and activity of various anticancer drugs [48,49] and these
new nitro compounds are shown to interact with Langmuir monolayers
as cell membrane models, including with molecular dynamic (MD)
simulations. The possible implications of these interactions for the
compounds bioactivity are discussed.
passed through a celite column to remove traces of NaIO3 and the filtrate
concentrated under reduced pressure, providing a colorless to slightly
yellow oil. This product was used in the next step without further pu-
rification (4.76 g).
2.1.3. Synthesis of ethyl (2Z)ꢀ 3-[(4S)ꢀ 2,2-dimethyl-1,3-dioxolan-4-yl]
prop-2-enoate (4)
A solution of (R)ꢀ 2,3-O-isopropylidenoglyceraldehyde (3) (2.20 g,
16.92 mmol) in methanol (24.20 mL) was added to a round-bottom
flask, forming a colorless solution and refrigerated to ꢀ 10 ◦C with
magnetic stirring. Then ethyl (triphenylphosphoranylidene) acetate
(5.89 g, 16.92 mmol) was added and the reaction stirred for 1 h at
ꢀ 10 ◦C. The solvent was removed under reduced pressure. The residue
was extracted, filtered with hot hexane and the extracts evaporated in
reduced pressure generating colorless oil. The product was purified on
preparative chromatography obtaining the pure product in 60.5% yield
(2.02 g). Spectral data: FT-IR (ATR): 2985, 2938, 1715, 1644, 1184,
1055, 1028, 855, 821, 511 cmꢀ 1; 1H NMR (90 MHz, CDCl3) δ ppm 6.25
(1 H, dd, J = 11.3, 5.8 Hz) 5.68 (1 H, dd, J = 11.3, 1.5 Hz) 5.32 (1 H,
qd, J = 6.6, 1.6 Hz) 4.22 (1 H, dd, J = 8.0, 6.9 Hz) 4.02 (1 H, q,
J = 7.3 Hz) 3.41 (1 H, dd, J = 8.0, 6.9 Hz) 1.26 (3 H, s) 1.21 (3 H, s)
1.13 (3 H, t, J = 7.3 Hz); 13C NMR (23 MHz, CDCl3) δ ppm 165.08,
150.19, 120.21, 109.32, 73.83, 69.35, 59.92, 31.71, 26.36, 25.22,
22.70, 13.95.
2. Experimental methods
2.1. Chemical synthesis of the PA precursors
Fig. 1 depicts the synthetic route from D-(+)-mannitol to ethyl (3S)ꢀ
3-((S)ꢀ 2,2-dimethyl-1,3-dioxolan-4-yl)ꢀ 4-nitropentadecanoate (mole-
cule 6), named “Nitro-C15-EED”, and (4S,5S)ꢀ 5-(hydroxymethyl)ꢀ 4-
((S)ꢀ 1-nitrododecyl)dihydrofuran-2(3H)-one (molecule 7), named
“Nitro-C12-GBL”. The production of molecules 6 and 7 was accom-
plished with the nephrosteranic acid synthesis methodology [29], from
D-(+)-mannitol (1) as starting molecule [50]. This synthetic route is
based on the chiron approach to produce enantiomericaly pure mole-
cules from cheap chiral natural sources, like carbohydrates [51,52].
Some steps were modified for improving the overall yield of the re-
actions. Briefly, the first two steps were optimized and a sequence of
selective protection to 2, followed by a oxidative cleavage (3) and used
immediately to avoid polymerization [53,54] in a Wittig reaction pro-
duced the enoate 4 with high Z stereoselectivity (10:1 Z:E). Nitroesther 6
was obtained via a Michael addition with 1-nitrododecane (5) (prepared
from 1-bromododecane by Kornblum reaction) [55] with high diaster-
eoselection (18:1 syn/anti). Cyclization of nitroesther 6 was performed
by acid hydrolysis to generate lactone 7. The molecules 6 and 7 used in
cytotoxic assays are in the form of a diastereoisomeric mixture at the
stereocenter in position Cα-NO2 due to the labile hydrogen. The nuclear
magnetic resonance (NMR) and infrared (IR) spectra of purified syn-
thetic compounds are presented in Supplementary Material 1. The
synthesis steps are described below.
2.1.4. Synthesis of 1-nitrododecane (5)
A solution of 1-bromododecane (10 g, 40.16 mmol) in DMSO
(31 mL) and sodium nitrite (5.5 g, 80.32 mmol), at 25 ◦C, was kept
under stirring for 22 h. The medium was extracted with 90 mL hexane
and the organic solution was then washed with water (3 × 30 mL) and
dried over anhydrous Na2SO4. The suspension was filtered and the so-
lution evaporated under reduced pressure providing the crude 1-nitro-
dodecane. The product was purified by preparative chromatography,
providing the product as a colorless liquid in 50% yield (4.3 g). Spectral
data: FT-IR (ATR): 2956, 2923, 2854, 1551, 1466, 1434, 1380, 1352,
721 cmꢀ 1
;
1H NMR (90 MHz, Without Solvent) δ ppm 4.36 (t,
J = 6.4 Hz, 2 H), 1.98 (br. s., 2 H), 1.28 (br. s., 18 H), 0.89 (br. s., 3 H);
13C NMR (23 MHz, without solvent) δ ppm 76.00, 32.45, 30.15, 29.87,
29.40, 27.86, 26.72, 23.18, 14.45.
2.1.1. Synthesis of 1,2:5,6-Di-O-isopropylidene-D-mannitol (2)
D-mannitol (1) (10.0 g, 54.96 mmol), anhydrous zinc chloride
(20.0 g, 146.62 mmol) and anhydrous acetone (0.27 mol Lꢀ 1 solution)
was mixed under argon atmosphere for 5 h. The reaction product was
poured in a solution of potassium bicarbonate (22.5 g) in water
(22.5 mL) under vigorous stirring and filtered with acetone (100 mL).
The solution was evaporated under reduced pressure. The resulting solid
was dissolved in diethyl ether (30 mL), transferred to a separating fun-
nel and the organic layer obtained. The aqueous layer was extracted
with diethyl ether (3 ×25 mL). The organic layers were dried over
Na2SO4, filtered and evaporated under reduced pressure. The solid was
purified in cold hexane (50 mL), filtered and dried, yielding a white
solid in 60% yield (8.64 g). Spectral data: FT-IR (ATR): 3463, 3309,
2.1.5. Synthesis of ethyl (3S)ꢀ 3-((S)ꢀ 2,2-dimethyl-1,3-dioxolan-4-yl)ꢀ
4-nitropentadecanoate (6)
A solution of ethyl (2Z)ꢀ 3-[(4S)ꢀ 2,2-dimethyl-1,3-dioxolan-4-yl]
prop-2-enoate (4) (Z-enoate) (1.3 g, 6.48 mmol) and 1-nitrododecane
(5) (1.67 g, 7.80 mmol), 26 mL in acetonitrile (0.25 mol Lꢀ 1 solution)
was contained in a flask under nitrogen atmosphere and magnetic stir-
ring at room temperature. DBU [1,8-Diazabicyclo(5.4.0)undec-7-ene]
(0.967 mL, 6.48 mmol) was added and the resulting orange solution
stirred for 24 h, then concentrated on a rotary evaporator. The residue
was purified by preparative chromatography, obtaining 61% yield
(1.64 g) in the form of a colorless liquid from the Z-enoate with the
presence of a mixture of syn/anti epimers in the proportion of 18:1 at Cα-
NO2. Spectral data: FT-IR (ATR): 2984, 2924, 2854, 1735, 1548, 1466,
1371, 1213, 1180, 1066, 858, 722 cmꢀ 1;1H NMR (90 MHz, CDCl3) δ
ppm 4.81 (t, J = 11.2 Hz, 1 H), 4.18 (m, 4 H), 3.64 (m, 2 H), 2.51 (m,
4 H), 1.91 (m, 9 H), 1.32 (m, 18 H), 0.87 (m, 3 H); 13C NMR (23 MHz,
CDCl3) δ ppm 171.74, 109.25, 87.85, 75.89, 67.11, 60.94, 41.74, 32.01,
31.18, 29.67, 29.43, 29.05, 26.28, 25.32, 22.77, 14.12.
1
2981, 2939, 2874, 1370, 1250, 1204, 1061, 945, 844 cmꢀ 1; H NMR
(90 MHz, CDCl3) δ ppm 4.08 (m, 6 H), 3.75 (t, J = 5.9 Hz, 2 H), 2.74 (d,
J=6.7 Hz, 2 H), 1.39 (s, 6 H), 1.42 (s, 6 H); 13C NMR (23 MHz, CDCl3) δ
ppm 109.41, 78.46, 77.06, 76.22, 75.66, 71.20, 66.78, 26.75, 25.23.
2.1.2. Synthesis of (R)ꢀ 2,3-O-isopropylidenoglyceraldehyde (3)
1,2:5,6-Di-O-isopropylidene-D-mannitol (2) (5.0 g, 19 mmol) was
solubilized in THF (tetrahydrofuran) (100 mL), a 10% sodium bicar-
bonate solution (2.6 mL) and a suspension of sodium periodate (11.42 g,
53.4 mmol) in water (13.00 mL) and THF (20.00 mL) were added. A
gelatinous precipitate was formed and the reaction mixture remained
under vigorous stirring for 1 h. Diethyl ether (5 mL) was added and the
supernatant filtered. The organic solution was evaporated under
reduced pressure and the residue solubilized in dichloromethane
(CH2Cl2) and dried with anhydrous sodium sulfate. This solution was
2.1.6. Synthesis of (4S,5S)ꢀ 5-(hydroxymethyl)ꢀ 4-((S)ꢀ 1-nitrododecyl)
dihydrofuran-2(3H)-one (7)
A solution containing ethyl (3S)ꢀ 3-((S)ꢀ 2,2-dimethyl-1,3-dioxolan-
4-yl)ꢀ 4-nitropentadecanoate (6) (0.5 g, 1.20 mmol) in methanol (4 mL,
0.3 mol Lꢀ 1) was prepared at room temperature and, with magnetic
stirring, 10% HCl solution (0.047 mL, 1.20 mmol) was added. After one
hour the solvent was evaporated and the residue was purified on a
3