Synthesis and Biological Evaluation of a Library of AGE-Related Amino Acid Triazole Crosslinkers

Article abstract of DOI:10.1002/ejoc.202000811

Three N-Boc-protected amino acids, l-serine, l-aspartic, and l-glutamic acid, were either converted into their methyl azidoalkanoates or various alkynes via Bestmann-Ohira strategy or via reaction with propargylamine and propargyl bromide, respectively. The Cu-catalyzed click reaction provided a library of amino acid based triazoles, which were further N-methylated to triazolium iodides or deprotected and precipitated as free amino acid triazole dihydrochlorides. The biological properties of all derivatives were investigated by cytotoxicity assay (against L929 mouse fibroblasts) and broth microdilution method (E. coli ΔTolC and S. aureus). First results reveal complete inactivity for triazolium iodides with cell viabilities and microbial growths nearly 100 %, indicating them as possible analogs of advanced glycation endproducts (AGEs).

Full text of DOI:10.1002/ejoc.202000811

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Triazole Amino Acids
Synthesis and Biological Evaluation of a Library of AGE-Related
Amino Acid Triazole Crosslinkers
Esra Icik,[a] Anthony Jolly,[a] Paul Löffler,[a] Nektarios Agelidis,[a] Bakiye Bugdayci,[a]
Luca Altevogt,[a,b] Ursula Bilitewski,[b] Angelika Baro,[a] and Sabine Laschat*[a]
Abstract: Three N-Boc-protected amino acids,
L-serine, L-aspar- amino acid triazole dihydrochlorides. The biological properties
tic, and -glutamic acid, were either converted into their methyl of all derivatives were investigated by cytotoxicity assay
L
azidoalkanoates or various alkynes via Bestmann-Ohira strategy (against L929 mouse fibroblasts) and broth microdilution
or via reaction with propargylamine and propargyl bromide, method (E. coli ΔTolC and S. aureus). First results reveal com-
respectively. The Cu-catalyzed click reaction provided a library plete inactivity for triazolium iodides with cell viabilities and
of amino acid based triazoles, which were further N-methylated microbial growths nearly 100 %, indicating them as possible an-
to triazolium iodides or deprotected and precipitated as free alogs of advanced glycation endproducts (AGEs).
Introduction
the crosslinking of peptides and proteins by bisamino acid tri-
azoles has more recently received growing attention for tailored
protein modifications, e.g. as ꢀ-turn mimetics and histidine
isosters.[5] Moreover, the synthetic precursors of amino acid tri-
azoles, i.e. the alkynylamino acids 3 are highly interesting com-
pounds themselves, because they are not only building blocks
for click chemistry[3,5,6,7] and Sonogashira cross-coupling for the
synthesis of desmosine, isodesmosine and related heterocyclic
cationic crosslinkers of connective tissue proteins, but also bio-
synthetic intermediates.[8] Very recently, the biosynthetic path-
Triazoles and in particular 1,2,3-triazoles are privileged scaffolds
in both organic synthesis, material science, catalysis, chemical
biology, and medicinal chemistry.[1a–1i] This is due to their con-
venient and convergent synthetic access from azides and alk-
ynes via Cu-catalyzed 1,3-dipolar cycloaddition (i.e. click reac-
tion) and Cu- or azide-free alternatives.[1e,1f] Furthermore, their
possibility to form CH-π interactions to generate mesoionic
carbenes makes them attractive as ligands to coordinate both
metal ions as well as biological matter such as enzymes. In addi-
tion, the use of triazoles for the isosteric replacement of amides
allows their use as pharmacophoric subunits in biologically ac-
tive compounds and drugs.[1] The corresponding triazolium cat-
ions were employed as functional ionic liquids, precursors of
mesoionic carbenes, and building blocks of supramolecular
assemblies.[2] While various triazole containing amino acids and
amino acid hybrid compounds 1, 2 have been developed, e.g.
for peptide drug conjugates, glycopeptides, peptide fluores-
cence labeling, and enzyme inhibitors,[3] dating back to 1996,[4]
way of amino acids containing terminal alkynes, e.g. L-ethynyl-
serine 4, propargylglycine 5, and ethynylglycine 6 were discov-
ered in the bacterium Streptomyces cattleya (Scheme 1).[9] Be-
sides the many histidine-containing peptides, crosslinking
amino acids and peptides carrying imidazole and imidazolium
units have also received much interest. For example, glyoxal-
lysine dimer (GOLD) 8, methylglyoxal-lysine dimer (MOLD) 9,
glyoxal- and methylglyoxal-derived imidazolium crosslinks
(GODIC, MODIC) 10, 11 and other more complex structures
have been extensively investigated.[10–14] These compounds are
members of a large class of advanced glycation endproducts
(AGEs) 7, which are biosynthetically formed by the Maillard re-
action of proteins and carbohydrates that result in protein
crosslinking. From a biological point of view, AGEs play an im-
portant role in such diverse areas as browning and processing
of food[11] as well as aging of tissue and protein-degenerative
diseases, associated with diabetes.[15]
[a] E. Icik, A. Jolly, P. Löffler, N. Agelidis, B. Bugdayci, L. Altevogt, Dr. A. Baro,
Prof. S. Laschat
Institut für Organische Chemie, Universität Stuttgart,
Pfaffenwaldring 55, 70569 Stuttgart, Germany
E-mail: sabine.laschat@oc.uni-stuttgart.de
https://www.ioc.uni-stuttgart.de/en/research/ak-laschat/
[b] L. Altevogt, Prof. U. Bilitewski
AG Compound Profiling and Screening, Helmholtz Zentrum für
Infektionsforschung,
Inhoffenstr. 7, 38124 Braunschweig, Germany
Natural imidazolium-based AGEs are useful medical markers
but often difficult to synthesize.[13] Therefore, we anticipated
that synthetic AGEs carrying a triazolium core instead of the
imidazolium unit might be a promising alternative, because
they should be readily available by Cu-catalyzed click reaction
of amino acid-derived alkynes and azides, respectively.[1h] It was
therefore our aim to provide a library of AGE analogs, carrying
a central triazole 12 or triazolium unit 12-MeX rather than an
E-mail: ursula.bilitewski@helmholtz-hzi.de
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.202000811.
© 2020 The Authors published by Wiley-VCH GmbH · This is an open access
article under the terms of the Creative Commons Attribution License, which
permits use, distribution and reproduction in any medium, provided the
original work is properly cited.
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in DMF in 72 %.[18] Subsequent iodination under Appel condi-
tions[17,19] and nucleophilic displacement with NaN3 in DMF[20]
yielded azide 21 in 81 % over two steps.
Scheme 2.
In a similar fashion NaBH4 reduction of aldehyde 14 gave
alcohol 18 in 84 % yield and was accompanied by lactone 19
formation (4 %). Lactone 19 could be recycled to 18 in 63 %.
Alcohol 18 was then converted in two steps into azide 22 in
72 % (over two steps). 18 was also converted into a mesylate
[21]
and treated with NaN3 to obtain azide 22 (Scheme S2).
The synthesis of
N-Boc-serine methyl ester 24a, which was available in two steps
from
-serine via N-Boc-serine 23 in 97 % (Scheme 3).[22] Methyl
L-serine-derived azide 25 commenced with
L
ester 24a was converted into the mesylate 24b[23] in 89 % fol-
lowed by treatment with NaN3 according to a method by
Shetty.[23] In agreement with previous work by Meffre[24] under
these conditions the desired azide 25 was obtained in 13 %
yield together with 21 % of alkene 26, which resulted from an
elimination reaction. The alternative route via Appel reaction
according to a method by Fenster[17,25] gave the respective iod-
ide in a disappointingly low yield of 26 % and was accompanied
by alkene 26 (4 %) (Scheme S3). When the iodide was submit-
ted to the SN2 reaction with NaN3 following a method by
Roth,[20] the elimination by-product dominated, giving a crude
Scheme 1.
1
mixture of azide 25/alkene 26 (12:88, by H-NMR, Scheme S3).
imidazolium unit. Moreover, the possibility for N-alkylation en-
ables the comparison of charged and neutral crosslinkers and
broadens the scope regarding structure-activity relationship
(SAR) studies. The realization of these “click AGEs” and their
preliminary biological investigation are discussed in the current
manuscript.
Results and Discussion
The synthesis of azides 21 and 22 derived from
L-aspartic acid
and -glutamic acid is shown in Scheme 2. The starting alde-
L
hydes 13 and 14 were accessible in three steps from the respec-
tive amino acids.[16] When aldehyde 13 was treated with NaBH4
according to the method by Adamczyk,[17] alcohol 15 was iso-
lated in only 24 % besides 52 % of the undesired δ-lactone 16.
Scheme 3.
The syntheses of amino acid alkynes are summarized in
Fortunately, the latter could be converted to alcohol 15 by Scheme 4 and Scheme 5. Aspartate-derived propargylglycine
treatment with CsOH in MeOH followed by reaction with MeI 28 was prepared from aldehyde 13 in 21 % yield via the Best-
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mann-Ohira strategy[24,26] utilizing ꢀ-keto-diazophosphonate tatively. The latter was then esterified yielding the desired alk-
27[24,27] for one-carbon homologation and K2CO3 as a base[23] yne 35 in 87 %.[22] When the intermediate free acid 34 was not
(Scheme 4).
isolated and the two-step reaction was carried out in one
pot,[32] the yield of 35 decreased to 30 %. However, by switch-
ing the sequence of Williamson etherification and esterification,
no trace of propargyl ether 35 was detected.
With the azides 21, 22, 25 and alkynes 28, 31, 35 in hand,
the Cu-catalyzed 1,3-dipolar cycloaddition was investigated
(Scheme 6).[33,34] After some optimization (for details see Table
S1, Supporting Information), azides 21, 22, 25 and alkynes 28,
31, 35 were treated with 2 mol-% CuSO4·5H2O, 20 mol-% so-
dium ascorbate in CH2Cl2/H2O (1:1) for 2–5 days at room tem-
perature to obtain a library of triazoles 36–39 (Scheme 6).
Under these conditions, the aspartic acid-derived azide 21
and the alkyne 31a reacted to triazole 37a in 56 %. Click reac-
tion of 21 and 31b gave the di-N-Boc-protected counterpart
37c in 45 % yield. Triazoles 37b,d obtained from azide 22 and
alkynes 31a,b were isolated in similar yields. Compared to the
di-N-Boc triazoles 37c,d based on aspartic acid derived alkyne
31b the corresponding glutamic acid derived alkyne 31c gave
the triazoles 36a,b in higher yields up to 85 %. In the click
reaction between serine-based alkyne 35 and the series of
azides, the glutamic acid-derived 22 gave the highest yield of
91 % for triazole 38c. The lowest yield was obtained for 38b
(9–58 %). Using tBuOH as a solvent for the formation of 38b
resulted in low yields (Scheme S1). Yields of triazoles 39 ranged
between 29 % for the aspartate-serine-derived click product
39a and 78 % for the glutamate-serine-derived triazole 39b.
Subsequent deprotection[35] of the triazoles 36–38 was
Scheme 4.
achieved with NaOH in MeOH, followed by treatment with 6
N
HCl in H2O to give the free bisamino acid triazole bishydro-
chlorides 36–39·2HCl in quantitative yield (Scheme 6). Com-
pounds 36–39·2HCl precipitated with 2–3 equiv. of NaCl. Aque-
ous solutions of 36–39·2HCl have acidic pH-values approving
the bishydrochlorides. In addition, protected triazoles 36–38
were N-alkylated with MeI in MeCN to give the N-methyl-triaz-
olium iodides 36-MeI – 38-MeI in 70 % to quantitative yield.[36]
Next, the biological properties of the click products were
investigated using the single concentration of 100 μ
M in the
primary assay. Both protected and unprotected triazole bis-
amino acids 36–39, 36–39·2HCl as well as the protected triaz-
olium iodides 36-MeI – 38-MeI were submitted to a standard
Alamar Blue cytotoxicity assay[37] against the L929 mouse fibro-
blast cell line. In addition, antimicrobial activities against the
Scheme 5.
The synthesis of amino acid alkynes 31 commenced with
saponification of known dimethyl esters 29[16,28] with KOH in
MeOH to the respective monomethyl esters 30. The reaction of
30 with propargylamine was performed using method A or B Gram-negative bacterium Escherichia coli ΔTolC and the Gram-
(Scheme 4). Alkyne 31a was isolated by both methods in com- positive bacterium Staphylococcus aureus were examined by
parable yields of 62 and 63 %. When mono ester 30b was measuring %growth via the broth microdilution method. The
treated with propargylamine in the presence of DCC and N- results in Table S2 revealed some general trends. Irrespective of
hydroxysuccinimide (NHS)[29] (method B, Scheme 4), ω-prop- the amino acid residues the unprotected triazole bisamino acids
argylamide 31b was obtained in 63 % together with 4 % of the
α-propargylamide 32b. In the case of monoester 30c, however,
the yield of ω-propargylamide 31c could be significantly im-
proved from 42 % (method A, Scheme 4)[30] to 82 % by addition
of NEt3 and NHS.
36–39·2HCl were weakly cytotoxic, showing cell viabilities of
50–61 %. However, no antimicrobial activities were observed.
Similar results were found for the N-Boc-protected triazole bis-
amino acid methyl ester 36–39. In contrast, the protected triaz-
olium iodides 36-MeI – 38-MeI were completely inactive in
As shown in Scheme 5, serine propargyl ether 35 was syn- both tests. In other words, for this series the cell viabilities and
thesized starting from N-Boc serine 33 by Williamson etherifica- antimicrobial growths were close to 100 %. Presumably, the tri-
tion with propargyl bromide and NaH[31] to give acid 34 quanti- azolium moiety seems to promote cell compatibility for both
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Scheme 6.
eukaryotic and prokaryotic cells. It should be emphasized that Experimental Section
the absence of cytotoxicity for triazolium salts is in a good
General: NMR spectra were recorded on Bruker Avance 300, 400,
agreement with a recent comparative SAR study on triazoles
500, and 700 MHz instruments. The chemical shifts (δ) are given in
ppm and were referenced to residual solvent signal. The signals
were assigned by using additional HSQC-, COSY- and HMBC experi-
ments. For easier comparison of NMR spectra, atom numbering may
deviate from the IUPAC nomenclature. IR spectra were recorded on
a Bruker FT-IR spectrometer ALPHA equipped with a diamond ATR
system (Platinum ATR) or a Bruker Vector 22 with MKII Golden Gate
and triazolium salts by da Silva.[38]
Conclusion
In the current work, a library of triazole bisamino acids has been
synthesized via Cu-catalyzed click reaction from serine-, Single Reflection Diamant ATR system. HRMS spectra were meas-
ured on a Bruker micrOTOF-Q spectrometer via electrospray ioniza-
tion (ESI). Melting points were measured on a Stuart SMP10 appara-
glutamic acid- and aspartic acid-derived azides and the corre-
sponding alkynes. The azides based on aspartic and glutamic
acid were synthesized with yields of 14–49 % over 6 steps.
Thereby lactone formations were not avoidable, but ring-open-
ing reactions were performed. The alkynes also based on these
two amino acids were obtained in 15–61 % yields over 4–5
steps by Bestmann-Ohira strategy and amidation reactions. The
serine derived azide was isolated over 3 steps in low yields of
3–11 %. However, the serine derived alkyne was synthesized
tus. Column chromatography was performed using silica gel 60
M
(Macherey-Nagel, grain size 40–63 μm). All chemicals were used as
purchased unless otherwise stated. CH2Cl2 and NEt3 were dried with
CaH2 by heating at reflux and subsequent distillation, THF was dried
with potassium with benzophenone as an indicator. Hexanes (b.p.
30–70 °C), EtOAc, CH2Cl2, and MeOH for chromatography were dis-
tilled prior to use. Moisture sensitive reactions were performed in
oven-dried glassware under N2 atmosphere. Methyl (2S)-2-[bis(tert-
with a high yield of 87 % performing a Williamson etherification butoxycarbonyl)amino]-4-azidobutanoate (21),[20] methyl (2S)-2-
(tert-butoxycarbonyl)amino-3-azidopropanoate (25),[20] methyl (2S)-
and esterification. Methylation of the N-Boc-protected triazole
amino acid methyl esters provided the corresponding triaz-
2-[bis(tert-butoxycarbonyl)amino]-pent-4-ynoate (28),[24] methyl
N2-(tert-butoxycarbonyl)-N4-prop-2-ynyl- -α-asparaginate (31a),[29,30]
L
olium iodides. According to preliminary biological studies fully
protected triazole bisamino acids 36–39 were weakly cytotoxic,
whereas the corresponding triazolium iodides 36-MeI – 38-MeI
did not show cytotoxic or antimicrobial activity, which makes
them suitable to study their potential as click AGE mimics with-
out interfering cytotoxic or antimicrobial activity. Work towards
this goal is in progress.
and methyl N-(tert-butoxycarbonyl)-O-prop-2-ynyl-
-serinate (35)[22,32]
L
were synthesized following the literature (see SI).
Methyl (2S)-2-[Bis(tert-butoxycarbonyl)amino]-5-azidopentano-
ate (22): According to ref.[20] iodide 20 (2.61 g, 5.71 mmol) and
NaN3 (0.75 g, 11.5 mmol) were dissolved in DMF (27 mL). The reac-
tion mixture was heated under reflux at 40 °C for 18 h. The solvent
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was removed under reduced pressure and the residue was dis- Methyl
solved in CHCl3 (30 mL). After evaporation of the solvent, the crude
glutaminate (31c): Method B: According to ref.[29] under N2-atmos-
product was purified by column chromatography on silica gel (hex- phere 30c (203 mg, 0.56 mmol) was dissolved in anhydrous CH2Cl2
anes/EtOAc, 8:1) to afford 22 (2.05 g, 5.52 mmol, 97 %) as a colorless (21 mL) and cooled to 0 °C. Then NHS (157 mg, 1.36 mmol) and
oil. [α]2D0 = –38.92 (c = 1.00 in CH2Cl2); 1H NMR (400 MHz, CDCl3): DCC (254 mg, 1.23 mmol) were added to the cooled solution and
N2,N2-Bis(tert-butoxycarbonyl)-N4-prop-2-ynyl-L-α-
δ = 1.50 [s, 18H; C(CH3)3], 1.60–1.75 (m, 2H; 3-Hα, 4-Hα), 1.90–2.02
(m, 1H; 4-Hꢀ), 2.14–2.26 (m, 1H; 3-Hꢀ), 3.24–3.39 (m, 2H; 5-H), 3.72
(s, 3H; 1-OMe), 4.86 ppm (dd, J = 9.4 Hz, 5.3 Hz, 1H; 2-H); 13C NMR
stirred for 15 min. After adding NEt3 (0.18 mL, 131 mg, 1.30 mmol)
and propargylamine (0.08 mL, 69 mg, 1.25 mmol), the reaction was
stirred for 1 d at r.t. The reaction mixture was filtered off and
(100 MHz, CDCl3): δ = 25.7 (C-4), 27.2 (C-3), 28.0 [2 × C(CH3)3], 51.0 washed with 0.1
M H2SO4 solution (2 × 40 mL), H2O (2 × 60 mL),
(C-5), 52.2 (1-OMe), 57.6 (C-2), 83.3 [2 × C(CH3)3], 152.1 (2 ×
and saturated NaHCO3 solution (2 × 40 mL). The organic phase was
dried with MgSO4 and filtered off. After removing the solvent, the
COOtBu), 171.0 ppm (C-1); FT-IR (ATR): ν = 2979 (m, br), 2936 (m, br),
˜
2096 (s), 1795 (w), 1746 (vs), 1699 (s), 1456 (w, br), 1367 (s), 1311 residue was purified by column chromatography on silica gel (hex-
(m), 1250 (s, br), 1169 (s), 1144 (vs), 1012 (w, br), 900 (w), 855 (w), anes/EtOAc, 3:1, phosphomolybdic acid), to afford 31c (182 mg,
812 (w), 782 (w, br), 667 (w), 464 (w) cm–1; MS (ESI): m/z = 395 [M
+ Na]+, 295 [M-Boc + Na]+, 239 [M – tert-butyl + Na]+, 195 [M-2 ×
Boc + Na]+, 173; HRMS (ESI): m/z calcd. for C16H28N4O6Na+: 395.1901
[M + Na]+, found 395.1892.
0.46 mmol, 82 %) as a white solid.
Method A: According to ref.[30] under N2-atmosphere 30c (118 mg,
0.33 mmol) was dissolved in anhydrous CH2Cl2 (3 mL) and cooled to
0 °C. Then DCC (72.0 mg, 0.35 mmol) and propargylamine (0.03 mL,
25.8 mg, 0.47 mmol) were added to the cooled solution and stirred
for 1 d at r.t. The reaction solution was filtered off and the solvent
was removed. The residue was taken up in EtOAc and filtered off
again. After evaporation of the solvent, the residue was purified by
column chromatography on silica gel (hexanes/EtOAc, 3:1) to afford
31c (54.0 mg, 0.14 mmol, 42 %) as a white solid. M.p. 119 °C; Rf =
0.19 (hexanes/EtOAc, 3:1); ] [α]2D0 = –29.0 (c = 1.00 in CH2Cl2);
1H NMR (400 MHz, CDCl3): δ = 1.50 [s, 18H; 2 × C(CH3)3], 2.13–2.21
(m, 1H; 3-Ha), 2.22 (t, J = 2.6 Hz, 1H; 3′-H), 2.30 (t, J = 7.5 Hz, 2H;
4-H), 2.44–2.56 (m, 1H; 3-Hb), 3.72 (s, 3H; OMe), 4.02–4.07 (m, 2H;
1′-H), 4.88 (dd, J = 8.9, 5.4 Hz, 1H; 2-H), 5.75–5.84 ppm (m, 1H; NH);
13C NMR (100 MHz, CDCl3): δ = 26.0 (C-3), 28.1 [C(CH3)3], 29.4 (C-1′
), 33.0 (C-4), 52.3 (OMe), 57.9 (C-2), 71.8 (C-3′), 79.7 (C-2′), 83.8
[C(CH3)3], 152.3 (COOtBu), 171.0 (C-1), 171.6 ppm (C-1); FT-IR (ATR):
Methyl N2,N2-Bis(tert-butoxycarbonyl)-N4-prop-2-ynyl-L-α-as-
paraginate (31b): According to ref.[29] under N2-atmosphere 30b
(2.03 g, 5.84 mmol) was dissolved in CH2Cl2 (203 mL) and cooled
to 0 °C. NHS (1.49 g, 12.9 mmol) and DCC (2.70 g, 13.1 mmol) were
added and stirred for 15 min. NEt3 (1.8 mL, 1.31 g, 13.0 mmol) and
propargylamine (0.81 mL, 0.70 g, 12.6 mmol) was added and stirred
for 1 d at r.t. The solution was filtered off and washed with 0.1
M
H2SO4 solution (4 × 100 mL), H2O (2 × 200 mL), and saturated
NaHCO3 solution (2 × 200 mL). The organic phase was dried with
MgSO4 and filtered off. After evaporation of the solvent, EtOAc was
added to the residue and cooled to –15 °C and filtered off. The
solvent was removed under reduced pressure and purified by col-
umn chromatography on silica gel (hexanes/EtOAc, 3:1) to afford
31b (1.86 g, 4.84 mmol, 63 %) as a colorless oil. Rf = 0.25 (hexanes/
= –41.8 (c =
1.47 in CH2Cl2); 1H NMR
ν = 465 (w), 665 (br, m), 785 (m), 853 (m), 1035 (m), 1116 (vs), 1140
EtOAc, 3:1); [α]D20
˜
(vs), 1168 (s), 1247 (s), 1312 (s), 1368 (vs), 1456 (m), 1535 (m), 1655
(s), 1700 (s), 1743 (vs), 1785 (m), 2980 (m), 3284 (br, m) cm–1. MS
(ESI): m/z = 421 [M + Na]+, 399, 343, 321, 299, 266, 243, 221, 199,
182, 166, 144; HRMS (ESI): m/z calcd. for C19H30N2O7Na+: 421.1945
[M + Na]+, found 421.1938.
(400 MHz, CDCl3): δ = 1.50 [s, 18H; 2 × C(CH3)3], 2.22 (t, J = 2.6 Hz,
1H; 3′-H), 2.62 (dd, J = 15.2, 6.1 Hz, 1H; 3-Ha), 3.11 (dd, J = 15.2,
7.3 Hz, 1H; 3-Hb), 3.72 (s, 3H; OMe), 4.02–4.08 (m, 2H; 1′-H), 5.45 (t,
J
=
6.7 Hz, 1H; 2-H), 5.93 ppm (brs, 1H; NH); 13C NMR
(100 MHz, CDCl3): δ = 28.1 [2 × C(CH3)3], 29.5 (C-1′), 38.1 (C-3), 52.7
(OMe), 55.4 (C-2), 71.8 (C-3′), 79.6 (C-2′), 83.7 [2 × C(CH3)3], 152.0
General Procedure for the Click Reaction: According to ref.[33,34]
azides 21, 22, 25 (1.00 mmol) and alkynes 28, 31, 35 (1.00 mmol)
were dissolved in water (10 mL) and CH2Cl2 (10 mL). CuSO4·5H2O
(0.01–0.02 mmol) and sodium ascorbate (0.1–0.2 mmol) were
added. After stirring the reaction for several hours, one or two more
times CuSO4·5H2O (0.01–0.02 mmol) and sodium ascorbate (0.1–
0.2 mmol) were added depending on the conversion shown on the
TLC and stirred for another certain time at r.t. After adding CH2Cl2
(30 mL), the aqueous layer was separated from the organic layer
and extracted with CH2Cl2 (3 × 20 mL). The combined organic layers
were washed with brine (40 mL), dried with MgSO4, and filtered off.
After evaporation of the solvent, the residue was purified by column
chromatography on silica gel. Due to the high viscosity of the click-
products removal of the solvent by lyophilization was difficult, so
spectra contain 3–29 % of EtOAc.
(2 × COOtBu), 169.4 (C-1), 170.9 ppm (C-4); FT-IR (ATR): ν = 568 (w),
˜
666 (w), 779 (w), 852 (m), 928 (w), 10001 (w), 1059 (w), 1116.3 (s),
1143 (vs), 1231 (s), 1274 (s), 1312 (s), 1368 (vs), 1437 (m), 1457 (m),
1540 (m), 1700 (s), 1747 (vs), 1787 (m), 2853 (w), 2932 (m), 2980
(m), 3299 (br, m) cm–1; MS (ESI): m/z = 431, 407 [M + Na]+, 385,
329, 307, 285, 251, 229, 207, 185, 125; HRMS (ESI): m/z calcd. for
C18H28N2O7Na+: 407.1789 [M + Na]+, found 407.1777.
As a side product methyl (3S)-3-[bis(tert-butoxycarbonyl)amino]-1-
prop-2′-ynylamido-butanoate 32b (87.0 mg, 0.23 mmol, 4 %) was
obtained as a white solid. M.p. 143 °C; Rf = 0.47 (hexanes/EtOAc,
3:1); [α]2D0 = –42.8 (c = 1.07 in CH2Cl2); 1H NMR (400 MHz, CDCl3):
δ = 1.51 [s, 18H; 2 × C(CH3)3], 2.21 (t, J = 2.5 Hz, 1H; 3′-H), 2.77 (dd,
J = 16.7, 6.9 Hz, 1H; 3-Ha), 3.33 (dd, J = 16.7, 6.5 Hz, 1H; 3-Hb), 3.69
(s, 3H; OMe), 3.95–4.04 (m, 1H; 1′-Ha), 4.07–4.16 (m, 1H; 1′-Hb), 5.19
(t, J = 6.8 Hz, 1H; 2-H), 6.09–6.16 ppm (m, 1H; NH); 13C NMR
(100 MHz, CDCl3): δ = 28.1 [2 × C(CH3)3], 29.6 (C-1′), 35.2 (C-3), 52.1
5-((1-((S)-4-(Methyloxy)-3-((Bis(tert-butoxycarbonyl)amino))-4-
oxobutyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(Bis(tert-butoxy-
(OMe), 56.2 (C-2), 72.0 (C-3′), 79.4 (C-2′), 84.3 [2 × C(CH3)3], 151.9 carbonylamino))-amidopentyl-methyl Ester (36a): From the az-
(2 × COOtBu), 169.0 (C-1), 171.8 ppm (C-4); FT-IR (ATR): ν = 411 (w),
ide 21 (46.0 mg, 0.13 mmol) and alkyne 31c (45.0 mg, 0.11 mmol)
in water (0.90 mL) and CH2Cl2 (0.90 mL), CuSO4·5H2O (1.23 mg,
4.93 μmol) and sodium ascorbate (8.52 mg, 43.0 μmol), 22 h;
CuSO4·5H2O (2.42 mg, 9.69 μmol) and sodium ascorbate (8.71 mg,
44.0 μmol), 22 h, 36a (72.0 mg, 95.1 μmol, 85 %), colorless oil. Rf =
˜
659 (w), 778 (w), 813 (w), 852 (m), 931 (w), 973 (w), 1027 (w), 1117
(s), 1140 (vs), 1166 (s), 1236 (s), 1307 (s), 1369 (s), 1438 (m), 1457
(m), 1479 (m), 1521 (m), 1698 (s), 1739 (vs), 1790 (m), 2933 (m),
2980 (m), 3279 (br, w) cm–1; MS (ESI): m/z = 449, 431, 407 [M + Na]+,
385, 349, 307, 285, 251, 229, 207, 185, 167, 153; HRMS (ESI): m/z 0.13 (hexanes/EtOAc, 1:2); [α]2D0 = –14.8 (c = 0.86 in CH2Cl2); 1H NMR
calcd. for C18H28N2O7Na+: 407.1789 [M + Na]+, found 407.1786.
(400 MHz, CDCl3): δ = 1.48 [s, 18H; 2 × C(CH3)3], 1.49 [s, 18H; 2 ×
5372 © 2020 The Authors published by Wiley-VCH GmbH
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European Journal of Organic Chemistry
C(CH3)3], 2.12–2.24 (m, 1H, 3′′-Ha), 2.28 (t, J = 7.2 Hz, 2H; 4′-H), 2.39–
1699 (s), 1737 (s), 1789 (w), 2255 (w), 2980 (w), 3331 (br, w) cm–1
;
2.59 (m, 2H; 3′′-Hb, 3′-Ha), 2.75–2.86 (m, 1H; 3′-Hb), 3.71 (s, 3H; OMe), MS (ESI): m/z = 665 [M + Na]+, 643, 599, 565, 543, 509, 487, 443,
3.73 (s, 3H; OMe), 4.37–4.60 (m, 4H; 4′′-H, 6-H), 4.82–4.96 (m, 2H; 431, 409, 387, 343, 313; HRMS (ESI): m/z calcd. for C28H46N6O11Na+:
2′-H, 2′′-H), 6.25–6.33 (m, 1H; NH), 7.62 ppm (s, 1H; 5-H); 13C NMR
(100 MHz, CDCl3): δ = 25.8 (C-3′′), 28.1 [4 × C(CH3)3], 31.0 (C-3′), 32.9
(C-4′), 34.6 (C-6), 48.3 (C-4′′), 52.3, 52.6 (OMe), 55.6, 57.7 (C-2′,
C-2′′), 83.5, 84.0 [4 × C(CH3)3], 123.4 (C-5), 144.2 (C-4), 152.1, 152.2
[4 × COOtBu], 170.3, 171.0, 172.2 ppm (C-1′, C-5′, C-1′′); FT-IR (ATR):
665.3117 [M + Na]+, found 665.3059.
4-((1-((S)-5-(Methyloxy)-4-((tert-butoxycarbonyl)amino)-5-oxo-
pentyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(bis(tert-butoxy-
carbonylamino))-amidobutyl-methyl Ester (37b): From the azide
22 (112 mg, 0.30 mmol) and alkyne 31a (114 mg, 0.40 mmol) in
water (1.90 mL) and CH2Cl2 (1.90 mL), CuSO4·5H2O (1.23 mg,
4.93 μmol) and sodium ascorbate (9.23 mg, 46.6 μmol), 19 h,
CuSO4·5H2O (1.80 mg, 7.21 μmol) and sodium ascorbate (10.8 mg,
54.6 μmol), 6 h, CuSO4·5H2O (9.00 mg, 3.60 μmol) and sodium
ascorbate (9.56 mg, 48.2 μmol), 18 h, 37b (129 mg, 0.20 mmol,
67 %) as a colorless oil. Rf = 0.14 (hexanes/EtOAc, 1:2); [α]2D0 = –11.6
(c = 1.00 in CH2 Cl2 ); 1 H NMR (400 MHz, CDCl3 ): δ = 1.44
[s, 9H; C(CH3)3], 1.49 [s, 18H; 2 × C(CH3)3], 1.86–2.03 (m, 3H; 4′′-H,
3′′-Ha), 2.07–2.18 (m, 1H; 3′′-Hb), 2.68 (dd, J = 17.0, 5.7 Hz, 1H;
3′-Ha), 3.05 (dd, J = 17.0, 4.2 Hz, 1H; 3′-Hb), 3.69 (s, 3H; OMe), 3.71
(s, 3H; OMe), 4.36 (t, J = 6.9 Hz, 2H; 5′′-H), 4.45–4.61 (m, 3H; 6-H,
2′-H), 4.86–4.93 (m, 1H; 2′′-H), 5.50–5.76 (m, 1H; NHBoc), 6.91–7.12
(m, 1H; NH), 7.53 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3):
δ = 26.9, 27.0 (C-3′′, C-4′′), 28.1, 28.4 [3 × C(CH3)3], 34.5 (C-6), 36.1
(C-3′), 50.8 (C-5′′), 50.9 (C-2′) 52.2, 52.5 (2 × OMe), 57.2 (C-2′′),
83.8 [4 × C(CH3)3], 123.6 (C-5), 143.8 (C-4), 152.3 [3 × COOtBu], 170.8,
ν = 413 (w), 461 (w), 647 (w), 665 (w), 731 (m), 782 (m), 853 (m),
˜
913 (w), 1013 (m), 1049 (m), 1141 (vs), 1166 (s), 1232 (s), 1367 (vs),
1437 (m), 1456 (m), 1529 (m), 1700(s), 1744 (vs), 1789 (m), 2035 (w),
2054 (w), 2115 (w), 2151 (w), 2185 (w), 2201 (w), 2266 (w), 2980
(m), 3366 (br w) cm–1; MS (ESI): m/z = 795, 779 [M + Na]+, 757, 695,
679, 657, 595, 579, 557, 523, 501, 457, 439, 401, 383, 357; HRMS
(ESI): m/z calcd. for C34H56N6O13Na+: 779.3798 [M + Na]+, found
779.3787.
5-((1-((S)-5-(Methyloxy)-4-((Bis(tert-butoxycarbonyl)amino))-5-
oxopentyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(Bis(tert-butoxy-
carbonylamino))-amidopentyl-methyl Ester (36b): From the az-
ide 22 (97.0 mg, 0.26 mmol) and the alkyne 31c (100 mg,
0.25 mmol) in water (1.50 mL) and CH2Cl2 (1.50 mL), CuSO4·5H2O
(2.00 mg, 8.01 μmol) and sodium ascorbate (11.6 mg, 58.6 μmol),
3 d, CuSO4·5H2O (1.15 mg, 4.61 μmol) and sodium ascorbate
(7.07 mg, 35.7 μmol), 6 h, CuSO4·5H2O (1.00 mg, 4.00 μmol) and
sodium ascorbate (5.30 mg, 26.7 μmol), 18 h, 36b (151 mg,
0.20 mmol, 80 %) as a colorless oil. Rf = 0.16 (hexanes/EtOAc, 1:2);
[α]2D0 = –33.1 (c = 0.71 in CH2Cl2); 1H NMR (700 MHz, CDCl3): δ =
1.48 [s, 36H; 4 × C(CH3)3], 1.86–1.95 (m, 1H; 3′′-Ha), 1.96–2.04 (m,
2H; 4′′-H), 2.09–2.23 (m, 2H; 3′′-Hb, 3′-Ha), 2.26–2.31 (m, 2H; 4′-H),
2.45–2.52 (m, 1H; 3′-Hb), 3.71 (s, 6H; 2 × OMe), 4.40 (t, 2H; 5′′-H),
4.48–4.59 (m, 2H; 6-H), 4.85–4.91 (m, 2H; 2′-H, 2′′-H), 6.38 (s, 1H;
NH), 7.63 ppm (s, 1H; 5-H); 13C NMR (175 MHz, CDCl3): δ = 25.8
(C-3′), 27.1 (C-3′′, C-4′′), 28.1 [4 × C(CH3)3], 32.9 (C-4′), 34.8 (C-6), 50.4
(C-5′′), 52.4, 52.5 (2 × OMe), 57.3, 57.7 (C-2′, C-2′′), 83.5,
83.7 [C(CH3)3], 123.0 (C-5), 144.2 (C-4), 152.2 (4 × COOtBu), 170.9,
171.4, 172.3 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR): ν = 462 (w), 647 (w),
˜
732 (m), 784 (m), 853 (m), 917 (w), 1027 (m), 1051 (m), 1165 (vs),
1249 (s), 1304 (m), 1367 (vs), 1438 (m), 1456 (m), 1521 (m), 1701 (s),
1739 (s), 1789 (m), 2934 (m), 2979 (m), 3349 (w) cm–1; MS (ESI):
m/z = 695, 679 [M + Na]+, 657, 613, 579, 557, 501, 445, 401, 357;
HRMS (ESI): m/z calcd. for C29H48N6O11Na+: 679.3273 [M + Na]+,
found 679.3272.
4-((1-((S)-4-(Methyloxy)-3-((Bis(tert-butoxycarbonyl)amino))-4-
oxobutyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(Bis(tert-butoxy-
carbonylamino))-amidobutyl-methyl Ester (37c): From the azide
21 (609 mg, 1.70 mmol) and alkyne 31b (646 mg, 1.68 mmol) in
water (9.50 mL) and CH2Cl2 (9.50 mL), CuSO4·5H2O (4.93 mg,
19.7 μmol) and sodium ascorbate (34.0 mg, 0.17 mmol), 22 h,
CuSO4·5H2O (5.48 mg, 21.9 μmol) and sodium ascorbate (35.0 mg,
0.18 mmol), 6 h, CuSO4·5H2O (5.35 mg, 21.4 μmol) and sodium
ascorbate (32.0 mg, 0.16 mmol), 20 h, 37c (560 mg, 0.75 mmol,
45 %) as a colorless oil. Rf = 0.02 (hexanes/EtOAc, 2:1); [α]2D0 = –24.1
(c = 1.07 in CH2Cl2); 1H NMR (400 MHz, CDCl3): δ = 1.45 [s, 36H; 4 ×
C(CH3)3], 2.38–2.51 (m, 1H; 3′′-Ha), 2.58 (dd, J = 15.1, 5.8 Hz, 1H;
3′-Ha), 2.73–2.86 (m, 1H; 3′′-Hb), 3.10 (dd, J = 15.1, 7.6 Hz, 1H;
3′-Hb), 3.70 (s, 3H; OMe), 3.72 (s, 3H; OMe), 4.31–4.66 (m, 4H; 4′′-H,
6-H), 4.89 (dd, J = 8.0, 5.8 Hz, 1H; 2′′-H), 5.50 (dd, J = 7.3, 5.8 Hz,
1H; 2′-H), 6.27 (t, J = 5.2 Hz, 1H; NH), 7.60 ppm (s, 1H; 5-H); 13C NMR
(100 MHz, CDCl3): δ = 28.1 [4 × C(CH3)3], 31.2 (C-3′′), 35.3 (C-6), 38.1
(C-3′), 47.8 (C-4′′), 52.6 (2 × OMe), 55.4 (C-2′), 55.7 (C-2′′), 83.6,
83.9 [4 × C(CH3)3], 122.6 (C-5), 144.7 (C-4), 151.9, 152.1 (4 × COOtBu),
171.0, 172.1 ppm (C-1′, C-5′, C-1′′). FT-IR (ATR): ν = 416 (w), 459 (w),
˜
784 (m), 854 (m), 1142 (vs), 1168 (s), 1250 (s), 1313 (m), 1368 (vs),
1457 (m), 1530 (m), 1702 (s), 1746 (vs), 1789 (m), 2980 (m), 3355
(br, w) cm–1; MS (ESI): m/z = 1542, 793 [M + Na]+, 693, 627, 571,
471, 415; HRMS (ESI): m/z calcd. for C35H58N6O13Na+: 793.3954 [M +
Na]+, found 793.3975.
4-((1′-((S)-1′′-(Methyloxy)-2′′-((tert-butoxycarbonyl)amino)-1′′-
oxobutyl)-1H-1′,2′,3′-triazol-4′-yl)methyl)-(2S)-2-(tert-butoxy-
carbonylamino)-amidobutyl-methyl Ester (37a): From the azide
21 (452 mg, 1.26 mmol) and alkyne 31a (357 mg, 1.26 mmol) in
water (7.00 mL) and CH2Cl2 (7.00 mL), CuSO4·5H2O (6.44 mg,
25.8 μmol) and sodium ascorbate (57.0 mg, 0.29 mmol), 18 h,
CuSO4 5 H2O (5.90 mg, 23.6 μmol) and sodium ascorbate (49 mg,
0.25 mmol), 5 h, CuSO4·5H2O (6.08 mg, 24.4 μmol) and sodium
ascorbate (42.0 mg, 0.21 mmol), 16 h, 37a (447 mg, 0.70 mmol,
56 %) as a colorless oil. Rf = 0.08 (hexanes/EtOAc, 1:1); [α]2D0 = +5.79
(c = 1.07 in CH2 Cl2 ); 1 H NMR (400 MHz, CDCl3 ): δ = 1.43
[s, 9H; C(CH3)3] (alkyne), 1.49 [s, 18H; 2 × C(CH3)3], 2.36–2.54 (m, 1H;
3′′-Ha), 2.68 (dd, J = 17.1, 5.6 Hz, 1H; 3′-Ha), 2.73–2.87 (m, 1H;
3′′-Hb), 3.04 (dd, J = 17.1, 3.9 Hz, 1H; 3′-Hb), 3.68 (s, 3H; OMe), 3.72
(s, 3H; OMe), 4.27–4.73 (m, 5H; 4′′-H, 6-H, 2-H), 4.89 (m, 1H; 2′′-H),
5.52–5.72 (m, 1H; NHBoc), 6.93–7.11 (m, 1H; CONH), 7.55 ppm (s,
1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 28.1, 28.4 [3 × C(CH3)3],
31.2 (C-3′′), 35.4 (C-6), 36.0 (C-3′), 47.7 (C-4′′), 50.9 (C-2′), 52.2 (OMe),
52.6 (OMe), 55.7 (C-2′′), 84.0 [3 × C(CH3)3], 122.4 (C-5), 144.7 (C-4),
169.8, 170.4, 170.9 ppm (C-1′, C-4′ C-1′′); FT-IR (ATR): ν = 464 (w),
˜
647 (w), 666 (w), 732 (m), 780 (m), 815 (w), 852 (m), 916 (m), 1000
(m), 1049 (m), 1114 (vs), 1141 (vs), 1167 (s), 1230 (s), 1312 (s), 1367
(vs), 1437 (m), 1457 (m), 1536 (m), 1699 (s), 1743 (vs), 1789 (m),
2980 (m), 3370 (br,w) cm–1; MS (ESI): m/z = 765 [M + Na]+, 743, 699,
665, 599, 565, 543, 509, 465, 443, 409, 387, 365, 343; HRMS (ESI):
m/z calcd. for C33H54N6O13Na+: 765.3641 [M + Na]+, found 765.3643.
4-((1-((S)-5-(Methyloxy)-4-((Bis(tert-butoxycarbonyl)amino))-5-
oxopentyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(bis(tert-butoxy-
152.1 (3 × COOtBu), 170.5, 170.9, 172.7 ppm (C-1′, C-4′, C-1′′). FT-IR carbonylamino))-amidobutyl-methyl Ester (37d): From the azide
(ATR): ν = 463 (w), 647 (m), 728 (vs), 781 (m), 852 (m), 912 (m), 1049 22 (271 mg, 0.70 mmol) and alkyne 31b (267 mg, 0.72 mmol) in
˜
(m), 1131 (vs), 1233 (s), 1366 (vs), 1438 (m), 1457 (m), 1518 (m),
water (8.30 mL) and CH2Cl2 (8.30 mL), CuSO4·5H2O (3.00 mg,
Eur. J. Org. Chem. 2020, 5368–5379
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12.0 μmol) and sodium ascorbate (25.0 mg, 0.13 mmol), 28 h,
CuSO4·5H2O (3.60 mg, 14.4 μmol) and sodium ascorbate (25.0 mg,
0.13 mmol), 4 d, 37d (276 mg, 0.36 mmol, 51 %) as a colorless oil.
ν = 416 (w), 463 (w), 575 (w), 647 (w), 733 (m), 781 (m), 810 (w),
˜
853 (m), 913 (w), 1047 (s), 1112 (vs), 1131 (vs), 1163 (vs), 1231 (s),
1366 (vs), 1438 (m), 1457 (m), 1502 (m), 1704 (vs), 1744 (vs), 1791
Rf = 0.15 (hexanes/EtOAc, 1:2); [α]2D0 = –38.3 (c = 1.07 in CH2Cl2); 1H (w), 2979 (m), 3369 (br, w) cm–1; MS (ESI): m/z = 654, 638 [M + Na]+,
NMR (400 MHz, CDCl3): δ = 1.47 [2 × s, 36H; 4 × C(CH3)3], 1.81–2.00 616, 572, 554, 538, 516, 482, 464, 438, 416, 382, 360, 338, 316; HRMS
(m, 3H; 4′′-H, 3′′-Ha), 2.04–2.23 (m, 1H; 3′′-Hb), 2.58 (dd, J = 15.0,
5.9 Hz, 1H; 3′-Ha), 3.09 (dd, J = 15.0, 7.5 Hz, 1H; 3′-Hb), 3.69 (2 × s,
6H; 2 × OMe), 4.35 (t, J = 7.0 Hz, 2H; 5′′-H), 4.43–4.59 (m, 2H; 6-H),
4.83–4.91 (m, 1 H, 2′-H), 6.41 (m, 1H; NH), 7.57 ppm (s, 1H; 5-H);
13C NMR (100 MHz, CDCl3): δ = 27.1 (C-3′′, C-4′′), 28.1 [4 × C(CH3)3],
35.1 (C-6), 38.1 (C-3′), 50.1 (C-5′′), 52.4, 52.6 (2 × OMe), 55.4 (C-2′),
57.4 (C-2′′), 83.6 [4 × C(CH3)3], 122.6 (C-5), 144.7 (C-4), 151.9,
152.3 [2 × COOtBu], 169.8, 170.9 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR):
(ESI): m/z calcd. for C27H45N5O11Na+: 638.3008 [M + Na]+, found
638.3031.
3-((1-((S)-5-(Methyloxy)-4-((Bis(tert-butoxycarbonyl)amino))-5-
oxopentyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(tert-butoxy-
carbonylamino)-oxopropyl-methyl Ester (38c): From the azide 22
(121 mg, 0.32 mmol) and alkyne 35 (92.0 mg, 0.36 mmol) in water
(1.90 mL) and CH2Cl2 (1.90 mL), CuSO4·5H2O (0.8 mg, 3.2 μmol) and
sodium ascorbate (6.66 mg, 33.6 μmol), 1 d, CuSO4·5H2O (1.00 mg,
4.00 μmol) and sodium ascorbate (7.21 mg, 40.4 mmol), 1 d, Cu-
SO4·5H2O (8.30 mg, 33.2 μmol) and sodium ascorbate (7.54 mg,
38.1 mmol), 1 d, 38c (183 mg, 0.29 mmol, 91 %) as a colorless oil.
Rf = 0.21 (hexanes/EtOAc, 1:1); [α]2D0 = –16.21 (c = 0.73 in CH2Cl2);
1H NMR (400 MHz, CDCl3): δ = 1.42 [s, 9H; C(CH3)3], 1.46 [s, 18H;
C(CH3)3], 1.82–2.23 (m, 4H; 3-H′′, 4-H′′), 3.68 (s, 3H; 1′′-OMe), 3.71 (s,
3H; 1-OMe), 3.72–3.74 (m, 1H; 3-Hα), 3.85–3.94 (m, 1H; 3-Hꢀ), 4.33–
4.39 (t, J = 6.9 Hz, 2H; 5′′-H), 4.39–4.45 (m, 1H; 2-H), 4.55–4.56 (m,
2H; 6′-H), 4.86 (dd, J = 8.9 Hz, 5.3 Hz, 1H; 2′′-H), 5.29–5.42 (m, 1H;
NH), 7.48 ppm (s, 1H; 5′-H); 13C NMR (100 MH z, CDCl3): δ = 27.0,
27.1 (C-3′′, C-4′′), 28.0 (2 × C(CH3)3), 28.3 (C(CH3)3), 49.8 (C-5′′), 52.3
(1′′-OMe), 52.5 (1-OMe), 53.9 (C-2), 57.2 (C-2′′), 64.9 (C-6′), 70.3 (C-
3), 80.0 (C(CH3)3), 83.5 [2 × C(CH3)3], 122.5 (C-5′), 144.4 (C-4′), 152.1
(2 × COOtBu), 155.5 (COOtBu), 170.8, 171.0 ppm (C-1, C′′-1); FT-IR
ν = 431 (w), 468 (w), 491 (w), 783 (m), 853 8m), 1003 (m), 1143 (vs),
˜
1168 (s), 130 (s), 1251 (s), 1312 (s), 1368 (vs), 1457 (m), 1534 (m),
1701 (s), 1748 (vs), 1789 (m), 1961 (w), 2007 (w), 2153 (w), 2980 (m),
3379 (br, w) cm–1; MS (ESI): m/z = 779 [M + Na]+, 757, 713, 679,
613, 579, 557, 557, 501, 457, 401, 357; HRMS (ESI): m/z calcd. for
C
34H56N6O13Na+: 779.3798 [M + Na]+, found 779.3768.
3-((1′-((S)-3-(Methyloxy)-2-((tert-butoxycarbonyl)amino)-3-oxo-
butyl)-1H-1,2,3-triazol-4-yl)methyl)-(2S)-2-(tert-butoxycarbonyl-
amino)-oxopropyl-methyl Ester (38a): From the azide 25 (515 mg,
2.11 mmol) and alkyne 35 (557 mg, 2.16 mmol) in water (22.0 mL)
and CH2Cl2 (22.0 mL), CuSO4·5H2O (5.8 mg, 23.2 μmol) and sodium
ascorbate (42.0 mg, 0.21 mmol), 20 h, CuSO4·5H2O (5.54 mg,
21.6 μmol) and sodium ascorbate (44 mg, 0.22 mmol), 5 h, Cu-
SO4·5H2O (5.23 mg, 20.8 μmol) and sodium ascorbate (40.0 mg,
0.20 mmol), 21 h, 38a (660 mg, 1.32 mmol, 63 %) as a white solid.
Rf = 0.04 (hexanes/EtOAc, 2:1). M.p. 82 °C; [α]2D0 = +29.6 (c = 1.13 in
CH2Cl2); 1H NMR (400 MHz, CDCl3): δ = 1.45 [s, 9H; 2 × C(CH3)3],
3.71–376 (m, 4H; 3′-Ha, 1-OMe), 3.79 (s, 3H; 1′′-OMe), 3.92 (dd,
J = 9.4, 3.3 Hz, 1H; 3′-Hb), 4.39–4.47 (m, 1H; 2′-H), 4.56–4.88 (m, 5H;
2′′-H, 3′′-H, 6-H), 5.26–5.59 (m, 2H; 2 × NHBoc), 7.47 ppm (s, 1H;
5-H); 13C NMR (100 MHz, CDCl3): δ = 28.4 [2 × C(CH3)3], 52.6 (2 ×
OMe), 53.9 (C-2′), 51.1, 53.3, 54.1, 64.8 (C-2′′, C-3′′, C-6), 70.5 (C-3′),
80.2, 80.9 [2 × C(CH3)3], 123.9 (C-5), 144.7 (C-4), 155.3, 155.6 (2 ×
(ATR): ν = 3374 (w, br), 2979 (m, br), 1790 (w), 1744 (s), 1703 (s),
˜
1502 (m, br), 1456 (m), 1438 (m), 1366 (s), 1305 (m), 1249 (s, br),
1163 (vs), 1131 (vs), 1114 (vs), 1048 (m), 915 (w), 853 (m), 783 (m),
733 (m), 648 (w, br), 465 (w, br) cm–1; MS (ESI): m/z = 652 [M + Na]+,
552 [M-Boc + Na]+, 496 [M-Boc-tert-butyl + Na]+, 452 [M-2 × Boc +
Na]+, 396 [M-2 × Boc-tert-butyl + Na]+; HRMS (ESI): m/z calcd. for
C
28H47N5O11Na+: 652.3164 [M + Na]+, found 652.3159.
3-(1-((S)-4-(Methyloxy)-3-((Bis(tert-butoxycarbonyl)amino))-4-
oxobutyl)-1H-1,2,3-triazol-4-yl)-(2S)-2-(Bis(tert-butoxycarbonyl-
amino))propyl-methyl Ester (39a): From the azide 21 (86.0 mg,
0.24 mmol) and alkyne 28 (79.0 mg, 0.24 mmol) in water (1.40 mL)
and CH2Cl2 (1.40 mL), CuSO4·5H2O (1.17 mg, 4.69 μmol) and sodium
ascorbate (7.66 mg, 38.7 μmol), 1 d, CuSO4·5H2O (1.17 mg,
4.69 μmol) and sodium ascorbate (11.0 mg, 55.5 μmol), 30 h,
CuSO4·5H2O (2.73 mg, 10.9 μmol) and sodium ascorbate (12.0 mg,
60.6 μmol), 19 h, 39a (47.0 mg, 0.07 mmol, 29 %) as a colorless oil.
Rf = 0.27 (hexanes/EtOAc, 2:1); [α]2D0 = –3.50 (c = 1.00 in CH2Cl2);
1H NMR (400 MHz, CDCl3): δ = 1.42, 1.47 [2 × s, 36H; 4 × C(CH3)3],
2.33–2.48 (m, 1H; 3′′-Ha), 2.66–2.82 (m, 1H; 3′′-Hb), 3.23–3.34 (m, 1H;
3′-Ha), 3.50–3.61 (m, 1H; 3′-Hb), 3.70 (s, 3H, OMe), 3.72 (s, 3H, OMe),
4.30–4.50 (m, 2H; 4′′-H), 4.82–4.92 (m, 1H; 2′′-H), 5.16–5.23 (m, 1H;
2′-H), 7.39 ppm (d, J = 2.7 Hz, 1H; 5-H); 13C NMR (100 MHz, CDCl3):
δ = 27.0 (C-3′), 28.0, 28.1 [4 × C(CH3)3], 31.3 (C-3′′), 47.5 (C-4′′), 52.4
(OMe), 52.5 (OMe), 55.7 (C-2′′), 58.1 (C-2′), 83.4, 83.8 [4 × C(CH3)3],
122.4 (C-5), 144.0 (C-4), 151.7, 152.1 (4 × COOtBu), 170.4, 170.7 ppm
COOtBu), 169.6, 171.2 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 462 (w), 646
˜
(w), 733 (m), 780 (w), 856 (w), 917 (w), 1027 (m), 1050 (s), 1108 (m),
1162 (vs), 1215 (s), 1249 8s), 1298 8m), 1367 (s), 1392 (m), 1438 (m),
1455 (m), 1506 (s), 1708 (vs), 1745 (s), 2977 (m), 3353 (br, w) cm–1
;
MS (ESI): m/z = 540, 524 [M + Na]+, 502, 468, 424, 402, 368, 346,
324; HRMS (ESI): m/z calcd. for C21H35N5O9Na+: 524.2327 [M + Na]+,
found 524.2315. The spectroscopic data are in accordance with the
literature.[33]
3-((1-((S)-4-(Methyloxy)-3-((Bis(tert-butoxycarbonyl)amino))-4-
oxobutyl)-1H-1,2,3-tri-azol-4-yl)methyl)-(2S)-2-(tert-butoxycarb-
onylamino)-oxopropyl-methyl Ester (38b): From the azide 21
(381 mg, 1.06 mmol) and alkyne 35 (264 mg, 1.03 mmol) in water
(11.0 mL) and CH2Cl2 (11.0 mL), CuSO4·5H2O (5.50 mg, 22.0 μmol)
and sodium ascorbate (40.0 mg, 0.20 mmol), 1 d, CuSO4·5H2O
(5.00 mg, 20.0 μmol) and sodium ascorbate (40 mg, 0.20 mmol), 3 d,
CuSO4·5H2O (2.90 mg, 11.6 μmol) and sodium ascorbate (20.0 mg,
0.10 mmol), 1 d, 38b (368 mg, 0.60 mmol, 58 %) as a colorless oil.
Rf = 0.06 (hexanes/EtOAc, 2:1); [α]2D0 = +1.68 (c = 1.07 in CH2Cl2);
1H-NMR (400 MHz, CDCl3): δ = 1.44 [s, 9H; C(CH3)3 (alkyne)], 1.50
[s, 18H; C(CH3)3 (azide)], 2.38–2.54 (m, 1H; 3′′-Ha), 2.74–2.89 (m, 1H;
3′′-Hb), 3.70–3.78 (m, 7H; 2 × OMe, 3′-Ha), 3.89–3.96 (m, 1H; 3′-Hb),
4.34–4.56 (m, 3H; 2′-H, 4′′-H), 4.60–4.70 (m, 2H; 6-H), 4.85–4.95 (m,
1H; 2′′-H), 5.28–5.46 (m, 1H; NH), 7.57 ppm (s, 1H; 5-H); 13C NMR
(100 MHz, CDCl3): δ = 28.1 [2 × C(CH3)3] (azide), 28.5 (C(CH3)3)
(alkyne), 31.2 (C-3′′), 47.8 (C-4′′), 52.6 (2 × OMe), 54.1 (C-2′), 55.7
(C-2′′), 65.0 (C-6), 70.6 (C-3′), 84.0 [3 × C(CH3)3], 123.0 (C-5), 144.7
(C-4), 152.2 (3 × COOtBu), 170.5, 171.2 ppm (C-1′, C-1′′); FT-IR (ATR):
(C-1′, C-1′′); FT-IR (ATR): ν = 440 (w), 464 (w), 577 (w), 647 (w), 666
˜
(w), 730 (s), 779 (m), 812 (w), 851 (m), 913 (m), 956 (w), 996 (m),
1011 (m), 1047 (m), 1087 (s), 1110 (vs), 1133 (vs), 1166 (s), 1226 (s),
1251 s), 1314 (m), 1366 (vs), 1437 (m), 1457 (m), 1554 (w), 1698 (s),
1742 (s), 1791 (m), 2980 (m) cm–1; MS (ESI): m/z = 7.24, 708, 686
[M + Na]+, 642, 608, 586, 542, 508, 486, 468, 452, 430, 408, 386,
374, 352, 330, 308, 286; HRMS (ESI): m/z calcd. for C31H51O12N5Na+:
686.3607 [M + Na]+, found 686.3604.
3-(1-((S)-5-(Methyloxy)-4-((Bis(tert-butoxycarbonyl)amino))-5-
oxopentyl)-1H-1,2,3-triazol-4-yl)-(2S)-2-(Bis(tert-butoxycarbon-
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ylamino))propyl-methyl Ester (39b): From the azide 22 (89.0 mg,
0.27 mmol) and alkyne 28 (107 mg, 0.29 mmol) in water (2.85 mL)
and CH2Cl2 (2.85 mL), CuSO4·5H2O (2.00 mg, 8.00 μmol) and sodium
ascorbate (16.6 mg, 83.8 μmol), 28 h, CuSO4·5H2O (2.60 mg,
10.4 μmol) and sodium ascorbate (19.6 mg, 98.9 mmol), 4 d, 39b
(149 mg, 0.21 mmol, 78 %) as a colorless oil. Rf = 0.63 (hexanes/
(m), 1446 (m), 1500 (m), 1708 (vs), 2921 (m) cm–1; MS (ESI): m/z =
391, 381, 365 [M + Na]+, 343 [M + H]+, 325, 310, 294, 279, 252,
236, 223, 214, 181, 165, 152, 140, 122; HRMS (ESI): m/z calcd. for
C13H22N6O5Na+: 365.1544 [M + Na]+, found 365.1535. Impurities
could not be removed because of the purification problems due to
the charged species.
EtOAc, 1:1); [α]D20
= –20.9 (c =
1.00 in CH2Cl2); 1H NMR
(1S)-3-{4-[(L-ꢀ-Aspartylamino)methyl]-1H-1,2,3-triazol-1-yl}-1-
(400 MHz, CDCl3): δ = 1.44 [s, 18H; 2 × C(CH3)3], 1.47 [s, 18H; 2 ×
C(CH3)3], 1.83–2.01 (m, 3H; 4′′-H, 3′′-Ha), 2.07–2.23 (m, 1H; 3′′-Hb),
3.28 (dd, J = 15.2, 9.8 Hz, 1H; 3′-Ha), 3.57 (dd, J = 15.2, 9.8 Hz, 1H;
3′-Hb), 3.70 (s, 3H; OMe), 3.73 (s, 3H; OMe), 4.23–4.39 (m, 2H; 5′′-H),
4.83–4.92 (m, 1H; 2′′-H), 5.19–5.25 (m, 1H; 2′-H), 7.35 ppm (s, 1H;
5-H); 13C NMR (100 MHz, CDCl3): δ = 28.0, 28.1 (4 × [C(CH3)3]), 49.8
(C-5′′), 52.4 (OMe), 57.4 (C-2′′), 58.1 (C-2′), 83.4, 83.6 [4 × [C(CH3)3],
122.4 (C-5), 143.9 (C-4), 151.7, 152.3 (4 × COOtBu), 170.7, 170.9 ppm
carboxypropan-1-aminium Dichloride (37a·2HCl/37c·2HCl):
From 37a (47.0 mg, 63.3 μmol) in MeOH (3.60 mL), 1
(0.16 mL, 0.16 mmol), 6 d; H2O (1.20 mL), 6 HCl (0.53 mL,
32.4 mmol), 5 d, 37a·2HCl (44.0 mg, quant.), yellow solid. From
37c (43.0 mg, 66.9 μmol) in MeOH (3.80 mL), 1 NaOH (0.19 mL,
0.19 mmol), 6 d; H2O (1.25 mL), 6 HCl (0.55 mL, 33.6 mmol), 5 d,
M NaOH
M
M
M
37c·2HCl (48.0 mg, quant.), yellow solid. [α]2D0 = +0.75 (c = 1.00 in
H2O); 1H NMR (400 MHz, CDCl3): δ = 2.50–2.77 (m, 2H; 3′′-H), 3.10
(t, J = 5.4 Hz, 2H; 3′-H), 4.12 (t, J = 6.6 Hz, 1H; 2′′-H), 4.44 (t, J =
5.4 Hz, 1H; 2′-H), 4.54 (s, 2H; 6-H), 4.71–4.76 (m, 2H; 4′′-H), 8.08 ppm
(s, 1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 30.1 (C-3′′), 34.2 (C-6),
34.4 (C-3′), 46.7 (C-4′′), 49.5 (C-2′), 50.1 (C-2′′), 124.7 (C-5), 144.1
(C-1′, C-1′′); FT-IR (ATR): ν = 416 (w), 442 (w), 464 (w), 493 (w), 583
˜
(w), 647 (w), 666 (w), 731 (s), 780 (m), 851 (m), 913 (m), 957 (w), 998
(m), 1048 8m), 1088 (s), 1133 (vs), 1167 (s), 1225 (s), 1250 (s), 1313
(m), 1366 (s), 1437 (w), 1457 (w), 1478 (w), 1555 (w), 1698 (s), 1743
(s), 1790 (w), 2937 (w), 2980 (m), 3140 (w) cm–1; MS (ESI): m/z =
722 [M + Na]+, 700, 656, 622, 600, 556, 522, 500, 466, 422, 400,
388, 366, 344, 322, 300; HRMS (ESI): m/z calcd. for C32H53N5O12Na+:
722.3583 [M + Na]+, found 722.3583.
(C-4), 170.7, 170.8, 170.9 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR): ν = 412
˜
(w), 471 (w), 517 (w), 579 (w), 621 (w), 786 (w), 848 (w), 1017 (m),
1056 (m), 1089 (m), 1155 (s), 1226 (vs), 1373 (m), 1437 (s), 1554 (m),
1662 (s), 1717 (vs), 1741 (vs), 2929 (s) cm–1; MS (ESI): m/z = 433,
399, 377, 353, 337, 315 [M – H]+, 297, 269, 200, 177, 155; HRMS
(ESI): m/z calcd. for C11H19N6O5+: 315.1411 [M – H]+, found 315.1406.
Impurities could not be removed because of the purification prob-
lems due to the charge species.
General Procedure for the Deprotection of Triazoles to Acids
36–39·2HCl: Analogous to ref.[35] a 1
M solution of NaOH (2.54 mL,
2.54 mmol) was added to a solution of the respective triazole 36–
39 (1.00 mmol) in MeOH (55 mL), and the reaction mixture stirred
at r.t. for several days. After concentration of the reaction mixture,
(1S)-3-{4-[(L-ꢀ-Aspartylamino)methyl]-1H-1,2,3-triazol-1-yl}-1-
carboxybutan-1-aminium Dichloride (37b·2HCl): From 37b
the residue was taken up in H2O (18.2 mL) and a 6
M solution of
HCl (8.00 mL) was added. The reaction mixture was stirred for sev-
eral days and subsequently concentrated under reduced pressure.
In the presence of the base, racemization is possible but it was not
checked.
(62.0 mg, 94.5 μmol) in MeOH (5.00 mL), 1
M NaOH (0.24 mL,
0.24 mmol), 2 d; H2O (1.65 mL), 6
M HCl (0.72 mL, 44.0 mmol), 3 d,
37b·2HCl (70.0 mg, quant.), white solid. [α]2D0 = +1.87 (c = 0.87 in
1
H2O); H NMR (400 MHz, CDCl3): δ = 1.84–2.25 (m, 2H; 3′′-H, 4′′-H),
3.08 (t, J = 5.3 Hz, 2H; 3′-H), 4.14 (t, J = 6.1 Hz, 1H; 2′′-H), 4.43 (t,
J = 5.3 Hz, 1H; 2′-H), 4.49–4.63 (m, 4H; 5′′-H, 6-H), 8.18 ppm (s, 1H;
5-H); 13C NMR (100 MHz, CDCl3): δ = 24.9 (C-4′′), 26.6 (C-3′′), 33.7
(C-6), 34.3 (C-3′), 49.5 (C-2′), 50.8 (C-5′′), 52.2 (C-2′′), 125.5 (C-5),
142.8 (C-4), 170.9, 171.4, 172.4 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR):
(1S)-1-Carboxy-3-{4-[(L-γ-glutamylamino)methyl]-1H-1,2,3-tri-
azol-1-yl}propan-1-aminium Dichloride (36a·2HCl): From 36a
(16.0 mg, 21.1 μmol) in MeOH (1.20 mL), 1
M NaOH (0.06 mL,
0.06 mmol), 2 d; H2O (0.40 mL), 6
M HCl (0.18 mL, 11.0 mmol), 3 d,
36a·2HCl (17.0 mg, quant.), white solid. [α]2D0 = +0.72 (c = 1.53 in
1
ν = 419 (w), 439 (w), 483 (w), 542 (w), 698 (m), 734 (m), 1118 (m),
˜
H2O); H NMR (500 MHz, CDCl3): δ = 2.06–2.16 (m, 1H; 3′-Ha), 2.18–
1168 (m), 1260 (m), 1377 (m), 1461 (m), 1714 (s), 1969 (w), 1995 (w),
2014 (w), 2062 (w), 2110 (w), 2151 (w), 2181 (w), 2210 (w), 2853 (s),
2924 (vs) cm–1; MS (ESI): m/z = 389, 371, 367, 353 [M + Na]–, 349,
327, 309, 292; HRMS (ESI): m/z calcd. for C12H22N6O5Na–: 353.1544
[M + Na]–, found 353.1544.
224 (m, 1H; 3′-Hb), 2.40–2.47 (m, 2H; 4′-H), 2.55–2.61 (m, 2H; 3′′-H),
4.02–4.05 (m, 1H; 2′′-H), 4.39–4.43 (m, 1H; 2′-H), 4.70–4.74 (m, 2H;
4′′-H), 4.81–4.83 (m, 2H; 6-H), 8.09 ppm (s, 1H; 5-H); 13C NMR
(175 MHz, CDCl3): δ = 25.6 (C-3′), 28.6 (C-4′), 30.0 (C-3′′), 33.1 (C-6),
46.5 (C-4′′), 50.0 (C-2′′), 56.4 (C-2′), 125.4 (C-5), 158.4 (C-5′), 175.9,
176.8 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 535 (w), 598 (w), 787 (w),
˜
(S)-2-{4-[((S)-2-Ammonio-2-carboxyethoxy]methyl)-1H-1,2,3-tri-
azol-4-yl}-1-carboxyethan-1-aminium Dichloride (38a·2HCl):
1056 (m), 1159 (s), 1212 (s), 1349 (m), 1418 (s), 1447 (s), 1510 (m),
1708 (vs), 1975 (w), 2928 (s) cm–1; MS (ESI): m/z = 397, 375, 367,
353 [M + Na]–, 335, 327, 252, 224, 176, 146, 128; HRMS (ESI): m/z
calcd. for C12H22N6O5Na–: 353.1544 [M + Na]–, found 353.1525.
From 38a (43.0 mg, 85.7 μmol) in MeOH (4.80 mL), 1
M NaOH
(0.22 mL, 0.22 mmol), 6 d; H2O (1.65 mL), 6 HCl (0.70 mL,
M
42.7 mmol), 5 d, 38a·2HCl (54.0 mg, quant.), yellow solid. [α]D20
=
+0.71 (c = 1.00 in H2O); 1H NMR (400 MHz, CDCl3): δ = 3.95–4.10
(m, 2H; 3′-H), 4.36 (t, J = 3.7 Hz, 1H; 2′-H), 4.75–4.77 (m, 3H;
2′′-H, 6-H), 5.10–5.16 (m, 2H; 3′′-H), 8.17 ppm (s, 1H; 5-H); 13C NMR
(100 MHz, CDCl3): δ = 48.9 (C-3′′), 52.6 (C-2′′), 53.1 (C-2′), 63.3 (C-6),
66.8 (C-3′), 126.4 (C-5), 143.8 (C-4), 168.7, 169.7 ppm (C-1′, C-1′′); FT-
(1S)-1-Carboxy-4-{4-[(L-γ-glutamylamino)methyl]-1H-1,2,3-tri-
azol-1-yl}butan-1-aminium Dichloride (36b·2HCl): From 36b
(18.0 mg, 23.3 μmol) in MeOH (1.40 mL), 1
M NaOH (0.07 mL,
0.07 mmol), 3 d; H2O (0.50 mL), 6 HCl (0.19 mL, 11.6 mmol), 2 d,
M
36b·2HCl (21.0 mg, quant.), white solid. [α]2D0 = +0.98 (c = 0.93 in
H2O); 1H NMR (400 MHz, CDCl3): δ = 1.81–2.31 (m, 6H; 3′-H, 3′′-H,
4′′-H), 2.45–2.56 (t, J = 7.2 Hz, 2H; 4′-H), 4.09–4.15 (m, 1H; 2′′-H),
4.24–4.34 (m, 1H; 2′-H), 4.51 (s, 2H; 6-H), 4.54–4.60 (m, 2H; 5′′-H),
8.23 ppm (s, 1H; 5-H); 13C NMR (175 MHz, CDCl3): δ = 25.0, 25.6,
26.5 (C-3′, C-3′′, C-4′′), 30.2 (C-4′), 32.9 (C-6), 49.8 (C-5′′), 52.2 (C-2′′),
56.4 (C-2′), 124.9 (C-5), 141.9 (C-4), 158.0 (C-5′), 171.4, 176.9 ppm
IR (ATR): ν = 422 (w), 506 (w), 614 (w), 842 (w), 906 (w), 1074 (m),
˜
1156 (m), 1215 (s), 1414 (m), 1505 (m), 1591 (m), 1736 (vs), 2833 (s)
cm–1; MS (ESI): m/z = 651, 607, 548, 498, 471, 439, 398, 340, 318,
296, 274 [M – H]+, 243, 231, 209, 187, 164, 141; HRMS (ESI): m/z
calcd. for C9H16N5O5+: 274.1146 [M – H]+, found 274.1144.
(S)-3-{4-[((S)-2-Ammonio-2-carboxyethoxy]methyl)-1H-1,2,3-tri-
(C-1′, C-1′′); FT-IR (ATR): ν = 413(w), 460 (w), 527 (w), 596 (w), 784
(w), 827 (w), 1030 (w), 1053 (w), 1155 (s), 1208 (s), 1345 (m), 1415
azol-4-yl}-1-carboxypropan-1-aminium Dichloride (38b·2HCl):
˜
From 38b (52.0 mg, 84.5 μmol) in MeOH (4.40 mL), 1
M NaOH
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(0.20 mL, 0.20 mmol), 6 d; H2O (1.50 mL), 6
M
HCl (0.65 mL,
General Procedure for the N-Alkylation of Triazoles 36–38: Anal-
39.7 mmol), 3 d, 38b·2HCl (57.0 mg, quant.), yellow solid. [α]D20
=
ogous to ref.[36] MeI (32.0–33.0 mmol) was added to a solution of
1
+0.6 (c = 1.00 in H2O); H NMR (400 MHz, CDCl3): δ = 2.47–2.69 (m, the respective triazole 36–38 (1.00 mmol) in MeCN (2.00 mL), and
2H; 3′′-H), 3.90–4.04 (m, 2H; 3′-H), 4.04–4.11 (m, 1H; 2′′-H), 4.30 (t, the reaction mixture was heated at 55 °C for 4–6 d. After removal
J = 3.6 Hz, 1H; 2′-H), 4.65–4.71 (m, 2H; 4′′-H), 4.73–4.76 (m, 2H;
6-H), 8.13 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 30.1
(C-3′′), 46.7 (C-4′′), 50.2 (C-2′′), 53.1 (C-2′), 63.3 (C-6), 66.8 (C-3′),
125.9 (C-5), 143.3 (C-4), 169.8, 170.8 ppm (C-1′, C-1′′); FT-IR (ATR):
of the solvent, the residue was purified by chromatography on HI
treated SiO2 with EtOAc, CH2Cl2, and CH2Cl2/MeOH (15:1).
1-((S)-3-(Bis(tert-butoxycarbonyl)amino)-4-methoxy-4-[((S)-4-
(bis(tert-butoxycarbonyl)amino)-5-methoxy-5-oxopentan-
amido)methyl]-3-methyl-1H-1,2,3-triazol-3-ium Iodide (36a-
MeI): From 36a (130 mg, 0.17 mmol) in MeCN (7.60 mL), MeI
(0.35 mL, 5.62 mmol), 5 d, yellow wax (149 mg, 0.17 mmol, quant.).
[α]2D0 = –12.9 (c = 0.76 in CH2Cl2); 1H NMR (400 MHz, CDCl3): δ =
1.44 [s, 18H; 2 × C(CH3)3], 1.47 [s, 18H; 2 × C(CH3)3], 2.16–2.44 (m,
4H; 3′-H, 4′-H), 2.45–2.58 (m, 1H; 3′′-Ha), 2.80–3.05 (m, 1H; 3′′-Hb),
3.66 (s, 3H; OMe), 3.71 (s, 3H; OMe), 4.46 (s, 3H; CH3), 4.56–4.72 (m,
4H; 6-H, 4′′-H), 4.78–4.97 (m, 2H; 2′′-H, 2′-H), 8.80 ppm (s, 1H; 5-H);
13C NMR (100 MHz, CDCl3): δ = 24.6 (C-3′), 28.1 [4 × C(CH3)3], 30.1
(C-3′′), 31.9 (C-6), 32.1 (C-4′), 39.6 (CH3), 51.7 (C-4′′), 52.2, 52.7 (2 ×
OMe), 55.1 (C-2′′), 58.1 (C-2′), 83.5, 84.3 [4 × C(CH3)3], 131.3 (C-5),
142.4 (C-4), 151.7, 152.0 [4 × COOtBu], 169.8, 170.8, 173.1 ppm
ν = 522 (m), 734 (w), 825 (w), 909 (w), 1056 (m), 1097 (m), 1155 (m),
˜
1218 (m), 1344 (w), 1422 (m), 1498 (m), 1600 (m), 1734 (s), 1934 (w),
2924 (s), 3367 (m) cm–1; MS (ESI): m/z = 458, 439, 413, 372, 350,
326, 310, 288 [M – H]+, 257, 239, 201, 149, 131; HRMS (ESI): m/z
calcd. for C10H18N5O5+: 288.1302 [M – H]+, found 288.1284.
(S)-4-{4-[((S)-2-Ammonio-2-carboxyethoxy]methyl)-1H-1,2,3-tri-
azol-4-yl}-1-carboxybutan-1-aminium Dichloride (38c·2HCl):
From 38c (42.0 mg, 66.7 μmol) in MeOH (3.80 mL), 1
(0.18 mL, 0.18 mmol), 3 d; H2O (1.30 mL), 6 HCl (0.55 mL,
33.6 mmol), 2 d, 38c·2HCl (47.0 mg, quant.), white solid. [α]D20
M NaOH
M
=
+7.28 (c = 1.00 in H2O); 1H NMR (400 MHz, CDCl3): δ = 1.86–2.09
(m, 4H; 3′′-H, 4′′-H), 4.00–4.08 (m, 2H; 3′-H), 4.13–4.17 (m, 1H; 2′′-H),
4.37 (t, J = 3.7 Hz, 1H; 2′-H), 4.59 (t, J = 6.7 Hz, 2H; 5′′-H), 4.73–4.77
(m, 2H; 6-H), 8.18 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3):
δ = 25.1 (C-4′′), 26.6 (C-3′′), 50.0 (C-5′′), 52.2 (C-2′′), 53.1 (C-2′), 63.1
(C-6), 66.8 (C-3′), 125.7 (C-5), 142.9 (C-4), 169.7, 171.5 ppm (C-1′, C-1′′);
(C-1′, C-5′, C-1′′); FT-IR (ATR): ν = 443 (w), 463 (w), 573 (w), 644 (m),
˜
665 (w), 728 (vs), 783 (m), 851 (m), 916 (m), 1014 (m), 1037 (m),
1092 (s), 1139 (vs), 1231 (s), 1366 (s), 1456 (m), 1525 (m), 1696
(m), 1740 (s), 1787 (m), 2196 (w), 2980 (m), 3235 (w) cm–1; MS (ESI
positive): m/z = 771 [M]+, 671; HRMS (ESI positive): m/z calcd. for
C35H59N6O13+: 771.4135 [M]+, found 771.4131; MS (ESI negative):
m/z = 127 [M]–; HRMS (ESI negative): m/z calcd. for I–: 126.9039
[M]–, found 126.9039.
FT-IR (ATR): ν = 530 (m), 614 (m), 781 (m), 829 (m), 1031 (s), 1053
˜
(s), 1106 (cs), 1156 (vs), 1211 (vs), 1342 (m), 1411 (s), 1450 (m), 1501
(s), 1595 (s), 1734 (vs), 1970 (w), 2852 (vs) cm–1; MS (ESI): m/z = 368,
346, 340, 324 [M + Na]+, 302 [M + H]+, 279, 259, 253, 237, 229, 215,
197, 187, 169, 158, 152, 141, 124, 116; HRMS (ESI): m/z calcd. for
11H19N5O5Na+: 324.1278 [M + Na]+, found 324.1270.
4-[((S)-4-(Bis(tert-butoxycarbonyl)amino)-5-methoxy-5-oxo-
pentanamido)methyl]-1-((S)-4-(bis(tert-butoxycarbonyl)amino)-
5-methoxy-5-oxopentyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide
(36b-MeI): From 36b (115 mg, 0.15 mmol) in MeCN (6.83 mL), MeI
(0.30 mL, 4.82 mmol), 5 d, yellow solid (115 mg, 0.13 mmol, 86 %).
C
(1S)-3-{4-[(2S)-2-Ammonio-2-carboxyethyl]-1H-1,2,3-triazol-1-
yl}-1-carboxypropan-1-aminium Dichloride (39a·2HCl): From
39a (26.0 mg, 37.9 μmol), in MeOH (2.20 mL), 1
M NaOH (0.10 mL,
0.10 mmol), 3 d; H2O (0.75 mL), 6 HCl (0.31 mL, 18.9 mmol), 2 d,
M
M.p. 57 °C; [α]2D0
= –26.8 (c =
0.82 in CH2Cl2); 1H NMR
39a·2HCl (26.0 mg, quant.), white solid. [α]2D0 = +0.22 (c = 0.93 in
H2O); 1H NMR (400 MHz, CDCl3): δ = 2.52–2.74 (m, 2H; 3′′-H), 3.49
(d, J = 6.0 Hz, 2H; 3′-H), 4.06–4.14 (m, 1H; 2′′-H), 4.48 (t, J = 6.0 Hz,
1H; 2′-H), 4.74 (t, J = 7.0 Hz, 2H; 4′′-H), 8.06 ppm (s, 1H; 5-H); 13C
NMR (100 MHz, CDCl3): δ = 25.6 (C-3′), 30.2 (C-3′′), 46.4 (C-4′′), 50.2
(C-2′′), 52.6 (C-2′), 125.4 (C-5), 141.0 (C-4), 170.9, 171.0 ppm (C-1′,
(400 MHz, CDCl3): δ = 1.47 [s, 18H; 2 × C(CH3)3], 1.50 [s, 18H; 2 ×
C(CH3)3], 1.88–2.02 (m, 1H; 3′′-Ha), 2.08–2.51 (m, 7H; 3′′-Hb, 4′′-H,
4′-H, 3′-H), 3.69 (s, 3H; OMe), 3.72 (s, 3H; OMe), 4.47 (s, 3H; CH3),
4.57–4.66 (m, 2H; 5′′-H), 4.67–4.73 (m, 2H; 6-H), 4.81–4.90 (m, 2H;
2′-H, 2′′-H), 8.85 ppm (s, 1H; 5-H); 13C-NMR (100 MHz, CDCl3): δ =
24.7 (C-3′), 26.1 (C-4′′), 26.9 (C-3′′), 28.2 [4 × C(CH3)3], 32.1 (C-4′, C-
6), 52.3 (OMe), 52.6 (OMe), 53.8 (C-5′′), 57.1 (C-2′′), 58.2 (C-2′), 83.7,
83.9 [4 × C(CH3)3], 131.3 (C-5), 142.7 (C-4), 151.9, 152.3 (4 × COOtBu),
C-1′′); FT-IR (ATR): ν = 420 (w), 521 (w), 617 (w), 811 (m), 1057 (m),
˜
1151 (m), 1208 (s), 120 (m), 1498 (m), 1593 (m), 1734 (vs), 2852 (m),
3373 (m) cm–1; MS (ESI): m/z = 324, 318, 308, 302, 296, 280 [M +
Na]+, 270, 258 [M + H]+, 253, 249, 237, 221, 212, 202, 197, 189, 181,
163, 149; HRMS (ESI): m/z calcd. for C9H15N5O4Na+: 280.1016 [M +
Na]+, found 280.1018.
170.6, 170.9, 173.3 ppm (C-1′, C-5′, C-1′′); FT-IR (ATR): ν = 461 (w),
˜
665 (w), 733 (w), 784 (m), 853 (m), 909 (w), 1013 (w), 1119 (s), 1142
(vs), 1250 (s), 1313 (m), 1367 (vs), 1456 (m), 1529 (m), 1698 (s), 1743
(s), 1787 (m), 2979 (m), 3221 (w) cm–1; MS (ESI positive): m/z =
(1S)-4-{4-[(2S)-2-Ammonio-2-carboxyethyl]-1H-1,2,3-triazol-1-
yl}-1-carboxybutan-1-aminium Dichloride (39b·2HCl): From 39b
786 [M]+, 685; HRMS (ESI positive): m/z calcd. for C36H61N6O13
:
+
785.4291 [M + Na]+, found 785.4289; MS (ESI negative): m/z = 157,
127 [M]–; HRMS (ESI negative): calcd. for I–: 126.9039 [M]–, found
126.9041.
(31.0 mg, 44.3 μmol) in MeOH (2.60 mL), 1
M NaOH (0.13 mL,
0.13 mmol), 3 d; H2O (0.85 mL), 6
M HCl (0.37 mL, 22.6 mmol), 2 d,
39b·2HCl (34.0 mg, quant.), white solid. [α]2D0 = +1.1 (c = 1.00 in
1
H2O); H NMR (400 MHz, CDCl3): δ = 1.83–2.24 (m, 4H; 3′′-H, 4′′-H),
1-((S)-3-(Bis(tert-butoxycarbonyl)amino))-4-methoxy-4-oxobut-
yl)-4-(((S)-3-((tert-butoxycarbonyl)amino)-4-methoxy-4-oxobut-
3.48 (d, J = 6.0 Hz, 2H; 3′-H), 4.14 (t, J = 6.0 Hz, 1H; 2′′-H), 4.47
(t, J = 6.0 Hz, 1H; 2′-H), 4.54 (t, J = 6.5 Hz, 2H; 5′′-H), 8.04 ppm (s, anamido)methyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide (37a-
1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 25.1 (C-4′′), 25.6 (C-3′), 26.7 MeI): From 37a (142 mg, 0.22 mmol) in MeCN (4.20 mL), MeI
(C-3′′), 49.6 (C-5′′), 52.3 (C-2′′), 52.5 (C-2′), 125.2 (C-5), 140.8 (C-4), (0.44 mL, 7.07 mmol), 6 d, orange solid (180 mg, 0.22 mmol, quant.).
170.8, 171.5 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 427 (w), 518 (m), 615
M.p. 66 °C; [α]2D0
=
+3.3 (c
(w), 670 (w), 836 (m), 1032 (m), 1056 (m), 1160 (m), 1207 (s), 1420 (400 MHz, CDCl3): δ = 1.43 (s, 9H; C(CH3)3), 1.49 [s, 18H; 2 × C(CH3)3],
(m), 1498 (m), 1593 (m), 1733 (vs), 2554 (s), 2615 (s), 2852 (s), 3379 2.46–2.54 (m, 1H; 3′′-Ha), 2.75–2.86 (m, 1H; 3′-Ha), 2.88–2.98 (m, 1H;
=
0.88 in CH2Cl2); 1H NMR
˜
(m) cm–1; MS (ESI): m/z = 338, 324, 316, 308, 300, 294 [M + Na]+, 3′′-Hb), 3.00–3.09 (m, 1H; 3′-Hb), 3.72 (s, 3H; OMe), 3.75 (s, 3H; OMe),
286, 280, 272 [M + H]+, 258, 249, 237, 227, 216, 188, 171, 157, 130,
116; HRMS (ESI): m/z calcd. for C10H17N5O4Na+: 294.1173 [M + Na]+,
found 294.1171.
4.40 (s, 3H; CH3), 4.47–4.59 (m, 1H; 2′-H), 4.63–4.71 (m, 2H; 4′′-H),
4.77–4.84 (m, 2H; 6-H), 4.85–4.96 (m, 1H; 2′′-H), 5.63–5.82 (m, 2H;
2 × NH), 8.90 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 28.1,
Eur. J. Org. Chem. 2020, 5368–5379
www.eurjoc.org
5376
© 2020 The Authors published by Wiley-VCH GmbH

Full Paper
doi.org/10.1002/ejoc.202000811
EurJOC
European Journal of Organic Chemistry
28.4, 28.5 [3 × C(CH3)3], 30.3 (C-3′′), 32.9 (C-6), 36.6 (C-3′), 39.3 (CH3),
51.8 (C-2′), 52.2 (C-4′′), 52.8 (OMe), 55.1 (C-2′′), 80.8, 84.6 [3 ×
5-methoxy-5-oxopentyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide
(37d-MeI): From 37d (110 mg, 0.15 mmol) in MeCN (3.20 mL), MeI
C(CH3)3], 131.2 (C-5), 142.5 (C-4), 152.1 (3 × COOtBu), 169.9, 171.9, (0.30 mL, 4.82 mmol), 5 d, yellow solid (124 mg, 0.14 mmol, 93 %).
172.3 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR): ν = 645 (w), 733 (m), 783
(m), 855 (m), 917 (w), 1024 (m), 1053 (m), 1164 (vs), 1250 (s), 1367
(vs), 1392 (s), 1438 (m), 1513 (s), 1709 (vs), 1988 (w), 2040 (w), 2092
M.p. 59 °C; [α]2D0 0.99 in CH2Cl2). 1H NMR
= –33.1° (c =
(400 MHz, CDCl3): δ = 1.48, 1.49 [2 × s, 36H; 4 × C(CH3)3], 1.86–2.00
(m, 1H; 3′′-Ha), 2.06–2.30 (m, 3H; 3′′-Hb, 4′′-H), 2.63 (dd, J = 15.5,
˜
(w), 2184 (w), 2979 (m), 3341 (m) cm–1; MS (ESI positive): m/z = 5.4 Hz, 1H; 3′-Ha), 3.23 (dd, J = 15.5, 8.5 Hz, 1H; 3′-Hb), 3.68 (s, 3H;
657 [M]+, 625, 601, 557, 525, 501, 469, 451, 413, 401, 369, 342, 310, OMe), 3.71 (s, 3H; OMe), 4.41 (s, 3H; CH3), 4.51–4.67 (m, 2H; 5′′-H),
286, 254; HRMS (ESI positive): m/z calcd. for C29H49N6O11+: 657.3454 4.77 (t, J = 5.9 Hz, 2H; 6-H), 4.81–4.94 (m, 1H; 2′′-H), 5.43–5.52 (m,
[M]+, found 657.3459; MS (ESI negative): m/z = 255, 241, 227, 157, 1H; 2′-H), 8.56 (t, J = 5.9 Hz, 1H; CONH), 8.85 ppm (s, 1H; 5-H);
127 [M]–; HRMS (ESI negative): m/z calcd. for I–: 126.9039 [M]–, found 13C NMR (100 MHz, CDCl3): δ = 26.1 (C-4′′), 26.9 (C-3′′), 28.2 [4 ×
126.9061.
C(CH3)3], 32.6 (C-6), 37.4 (C-3′), 39.2 (CH3), 52.6 (2 × OMe), 53.8
(C-5′′), 55.1 (C-2′), 57.0 (C-2′′), 83.8, 83.9 [3 × C(CH3)3], 130.8 (C-5),
142.9 (C-4), 151.6, 152.4 [3 × COOtBu], 170.6, 170.8, 171.1 ppm
1-((S)-4-(Bis(tert-butoxycarbonyl)amino))-5-methoxy-5-oxo-
pentyl)-4-(((S)-3-((tert-butoxycarbonyl)amino)-4-methoxy-4-
oxobutanamido)methyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide
(37b-MeI): From 37b (146 mg, 0.22 mmol) in MeCN (4.20 mL), MeI
(0.45 mL, 7.23 mmol), 5 d, yellow solid (158 mg, 0.20 mmol, 90 %).
(C-1′, C-4′, C-1′′); FT-IR (ATR): ν = 443 (w), 464 (w), 645 (w), 732 (m),
˜
781 (w), 851 (m), 917 (w), 1001 (w), 1119 (s), 1142 (vs), 1167 (s),
1232 (s), 1314 (m), 1367 (vs), 1456 (m), 1536 (w), 1697 (s), 1743 (vs9,
1787 (m), 2980 (m), 3183 (w) cm–1; MS (ESI positive): m/z = 771 [M]+,
739, 671, 639, 571, 539, 515; HRMS (ESI positive): m/z calcd. for
M.p. 64 °C; [α]2D0
= –6.4 (c =
1.01 in CH2Cl2); 1H NMR
(400 MHz, CDCl3): δ = 1.44 [s, 9H; C(CH3)3], 1.49 [s, 18H; 2 × C(CH3)3],
1.89–1.98 (m, 1H; 3′′-Ha), 2.08–2.22 (m, 3H; 3′′-Hb, 4′′-H), 2.83 (dd,
J = 16.7, 4.2 Hz, 1H; 3′-Ha), 3.06 (dd, J = 16.7, 5.5 Hz, 1H; 3′-Hb), 3.65
(s, 3H; OMe), 3.70 (s, 3H; OMe), 4.40 (s, 3H; CH3), 4.47–4.56 (m, 1H;
2′-H), 4.60 (t, J = 7.1 Hz, 2H; 5′′-H), 4.77–4.83 (m, 2H; 6-H), 4.83–4.88
(m, 1H; 2′′-H), 5.73 (d, J = 8.3 Hz, 1H; NHBoc), 8.57–8.72 (m, 1H;
CONH), 8.93 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3): δ = 26.1
(C-4′′), 26.8 (C-3′′), 28.1, 28.5 [3 × C(CH3)3], 33.0 (C-6), 36.6 (C-3′),
39.3 (CH3), 51.1 (C-2′), 52.2 (OMe), 52.5 (OMe), 53.8 (C-5′′), 57.0
(C-2′′), 80.7, 83.9 [3 × C(CH3)3], 131.0 (C-5), 142.5 (C-4), 152.3
[3 × COOtBu], 170.7, 171.9, 172.3 ppm (C-1′, C-4′, C-1′′); FT-IR (ATR):
C
35H59N6O13+: 771.4135 [M]+, found 771.4139; MS (ESI negative):
m/z = 227, 216, 181, 171, 157, 143, 127 [M]–, 121, 113; HRMS (ESI
negative): m/z calcd. for I–: 126.9039 [M]–, found 126.9057.
4-[((S)-2-((tert-Butoxycarbonyl)amino)-3-methoxy-3-oxoprop-
oxy)methyl]-1-((S)-2-((tert-butoxycarbonyl)amino)-3-methoxy-
3-oxopropyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide (38a-MeI):
From 38a (136 mg, 0.27 mmol) in MeCN (5.00 mL), MeI (0.54 mL,
8.67 mmol), 6 d, brown solid (119 mg, 0.19 mmol, 70 %). M.p. 63 °C;
[α]2D0 = –11.6 (c = 0.94 in CH2Cl2). 1H NMR (400 MHz, CDCl3): δ =
1.41 [s, 9H; C(CH3)3], 1.43 [s, 9H; C(CH3)3], 3.77 (s, 3H; OMe), 3.82 (s,
3H; OMe), 3.86–4.05 (m, 2H; 3′-H), 4.30 (s, 3H; CH3), 4.44–4.53 (m,
1H; 2′-H), 4.75–4.87 (m, 1H; 2′′-H), 4.93 (s, 2H; 6-H), 5.05–5.30 (m,
2H; 3′′-H), 5.37 (d, J = 5.6 Hz, 1H; NHC-2′), 6.43 (d, J = 6.6 Hz, 1H;
NHC-2′′), 9.15 ppm (s, 1H; 5-H); 13C NMR (100 MHz, CDCl3):
δ = 28.2 [C(CH3)3], 28.3 [C(CH3)3], 39.6 (CH3), 52.9 (2 × OMe), 53.4
(C-2′′), 53.7 (C-2′), 53.9 (C-3′′), 61.3 (C-6), 71.6 (C-3′), 80.3 [C(CH3)3],
80.8 [C(CH3)3], 131.6 (C-5), 139.9 (C-4), 155.3, 155.5 (2 × COOtBu),
ν = 462 (w), 644 (w), 731 (s), 783 (m), 852 (m), 917 (m), 1024 (m),
˜
1120 (s), 1142 (vs), 1162 (s), 1251 (s), 1312 (m), 1366 (s), 1437 (m),
1455 (m), 1509 (m), 1697 (s), 2979 (m), 3368 (w) cm–1; MS (ESI posi-
tive): m/z = 671 [M]+, 639, 615, 583, 571, 539, 515, 483, 465, 439,
415, 383, 310, 286, 254; HRMS (ESI positive): m/z calcd.
for C30H51N6O11+: 671.3610 [M]+, found 671.3612; MS (ESI nega-
tive): m/z = 241, 227, 157, 127 [M]–; HRMS (ESI negative): m/z calcd.
for I–: 126.9039 [M]–, found 126.9038.
168.8, 170.6 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 646 (w), 733 (w), 733
˜
(w), 782 (w), 853 (w), 1027 (m), 1067 8m), 1111 (m), 1163 (vs), 1251
(s), 1305 (m), 1367 (s), 1393 (m), 1438 (m), 1510 (s), 1706 (vs), 1742
(s), 2006 (w), 2165 (w), 2978 (m), 3368 (m) cm–1; MS (ESI positive): m/
z = 516 [M]+, 460, 404, 360, 337, 316, 281, 259; HRMS (ESI positive):
m/z calcd. for C22H38N5O9+: 516.2664 [M]+, found 516.2662; MS (ESI
negative): m/z = 157, 127 [M]–, 113; HRMS (ESI negative): m/z calcd.
for I–: 126.9039 [M]–, found 126.9054.
4-((S)-3-(Bis(tert-butoxycarbonyl)amino))-4-methoxy-4-oxo-
butanamido)methyl)-1-((S)-3-(bis(tert-butoxycarbonyl)amino)-
4-methoxy-4-oxobutyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide
(37c-MeI): From 37c (189 mg, 0.25 mmol) in MeCN (4.80 mL), MeI
(0.51 mL, 8.19 mmol), 6 d, yellow solid (211 mg, 0.24 mmol, 96 %).
M.p. 62 °C; [α]2D0
= –15.3 (c =
1.05 in CH2Cl2); 1H NMR
(400 MHz, CDCl3): δ = 1.48 [s, 18H; C(CH3)3], 1.49 [s, 18H; C(CH3)3],
2.41–2.57 (m, 1H; 3′′-Ha), 2.58–2.68 (m, 1H; 3′-Ha), 2.85–3.00 (m, 1H;
3′′-Hb), 3.17–3.30 (m, 1H; 3′-Hb), 3.68 (s, 3H; OMe), 3.73 (s, 3H; OMe),
4.42 (s, 3H; CH3), 4.59–4.94 (m, 6H; 4′′-H, 2′′-H, 6-H), 5.48 (t, J =
6.7 Hz, 1H; 2′-H), 8.43–8.57 (m, 1H; NH), 8.81–8.84 ppm (m, 1H; 5-
H); 13C NMR (100 MHz, CDCl3): δ = 28.1 [4 × C(CH3)3], 30.3 (C-3′′),
32.5 (C-6), 37.4 (C-3′), 39.3 (CH3), 51.8 (C-4′′), 52.5 (OMe), 52.8 (OMe),
55.1 (C-2′, C-2′′), 83.8, 84.5 [4 × [C(CH3)3], 130.9 (C-5), 142.8 (C-4),
151.5, 152.1 (4 × COOtBu), 169.8 (C-4′), 170.8, 171.0 ppm (C-1′, C-1′′);
1-((S)-3-(Bis(tert-butoxycarbonyl)amino)-4-methoxy-4-oxobut-
yl)-4-(((S)-2-((tert-butoxycarbonyl)amino)-3-methoxy-3-oxo-
propoxy)methyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide (38b-
MeI): From 38b (189 mg, 0.31 mmol) in MeCN (5.53 mL), MeI
(0.62 mL, 9.96 mmol), 6 d, orange wax (202 mg, 0.27 mmol, 87 %).
[α]2D0 = +4.9° (c = 1.19 in CH2Cl2); 1H NMR (400 MHz, CDCl3): δ =
1.43, 1.50 [2 × s, 27H; C(CH3)3], 2.44–2.58 (m, 1H; 3′′-Ha), 2.87–3.03
(m, 1H; 3′′-Hb), 3.73 (s, 3H; OMe), 3.76 (s, 3H; OMe), 3.88–3.95 (m,
1H; 3′-Ha), 3.98–4.05 (m, 1H; 3′-Hb), 4.31 (s, 3H; CH3), 4.44–4.57 (m,
1H; NH), 4.83 (t, J = 6.8 Hz, 2H; 4′′-H), 4.88 (t, J = 6.7 Hz, 1H; 2′′-H),
5.04 (s, 2H; 6-H), 5.31–5.43 (m, 1H; 2′-H), 9.26 ppm (s, 1H; 5-H);
13C NMR (100 MHz, CDCl3): δ = 28.1, 28.4 [3 × C(CH3)3], 30.4 (C-3′′),
39.5 (CH3), 52.1 (C-4′′), 52.8 (2 × OMe), 53.0 (C-2′), 55.1 (C-2′′), 61.5
(C-6), 71.8 (C-3′), 84.5 [3 × C(CH3)3], 131.3 (C-5), 140.3 (C-4), 152.1
FT-IR (ATR): ν = 446 (w), 664 (w), 734 (w), 782 (w), 850 (w), 915 (w),
˜
1000 (w), 1119 (s), 1143 (vs), 1166 (s), 1234 (s), 1272 (s), 1315 (m),
1367 (vs), 1456 (m), 1532 (m), 1699 (s), 1744 (vs), 1787 (m), 2134
(w), 2980 (m), 3226 (w) cm–1; MS (ESI positive): m/z = 757 [M]+, 725,
657, 625, 601, 557, 525, 501, 483, 469, 451, 401, 369, 310, 286; HRMS
(ESI positive): m/z calcd. for C34H57N6O13N+: 757.3978 [M]+, found
757.3981; MS (ESI negative): m/z = 265, 255, 241, 227, 157, 127
[M]–; HRMS (ESI negative): m/z calcd. for I–: 126.9039 [M]–, found
126.9047.
(3 × COOtBu), 170.7 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 578 (w), 783
˜
(w), 852 (w), 1117 (s), 1144 (vs), 1164 (vs), 1248 (s), 1367 (vs), 1456
(m), 1512 (m), 1705 (vs), 1744 (vs), 2024 (w), 2157 (w), 2979 (m),
4-((S)-3-(Bis(tert-butoxycarbonyl)amino))-4-methoxy-4-oxo- 3384 (w) cm–1; MS (ESI positive): m/z = 630 [M]+, 574, 530, 474, 456,
+
butanamido)methyl)-1-((S)-4-(bis(tert-butoxycarbonyl)amino)-
374, 315, 259; HRMS (ESI, positive): m/z calcd. for C28H48N5O11
:
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630.3345 [M]+, found 630.3344; MS (ESI negative): m/z = 209, 157,
141, 127 [M]–; HRMS (ESI negative): m/z calcd. for I–: 126.9039 [M]–,
found 126.9048.
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1-((S)-4-(Bis(tert-butoxycarbonyl)amino)-5-methoxy-5-oxopent-
yl)-4-(((S)-2-((tert-butoxycarbonyl)amino)-3-methoxy-3-oxo-
propoxy)methyl)-3-methyl-1H-1,2,3-triazol-3-ium Iodide (38c-
MeI): From 38c (190 mg, 0.30 mmol) in MeCN (5.40 mL), MeI
(0.60 mL, 1.40 g, 9.6 mmol), 5 d, yellow wax (210 mg, 0.27 mmol,
90 %); Rf = 0.37 (CH2Cl2/MeOH, 15:1). [α]2D0 = –6.43 (c = 1.00 in
CH2Cl2); 1H NMR (400 MHz, CDCl3): δ = 1.44 [s, 9H; C(CH3)3], 1.50 [s,
18H; 2 × C(CH3)3], 1.60–1.87 (m, 2H; 3′′-H),1.92–2.04 (m, 2H; 4′′-H),
2.12–2.27 (m, 3H; CH3) 3.72 (s, 3H; OMe), 3.78 (s, 3H; OMe), 3.91–
3.96 (m, 1H; 3′-H), 4.37–4.55 (m, 4H; 2′-H, 5′′-H), 4.74–4.80 (m, 2H;
6-H), 4.85–4.90 (m, 1H; 2′′-H), 5.31–5.38 (m, 1H; NH), 9.34 ppm (s,
1H; 4-H); 13C NMR (100 MHz, CDCl3): δ = 26.1 (C-3′′), 26.5 (C-4′′),
28.0 [(2 × C(CH3)], 28.3 [(C(CH3)], 39.6(C-5′′), 52.4 (OMe), 52.8 (OMe),
53.7 (C-2′), 57.0 (C-2′′), 61.3 (C-6), 71.4 (C-3′), 80.2 [N(CH3)],
83.7 [(C(CH3)], 130.8 (C-4), 140.0 (C-5), 152.1 (2 × COOtBu), 155.3
[4]
[5]
(COOtBu), 170.5 ppm (C-1′, C-1′′); FT-IR (ATR): ν = 2979 (w), 2381
˜
(w), 2175 (w), 2155 (w), 2003 (w), 1959 (w), 1742 (s), 1703 (s), 1507
(m), 1456 (m), 1437 (m), 1366 (m), 1309 (m), 1248 (m), 1160 (s), 1114
(s), 919 (w), 850 (m), 781 (m), 730 (m), 640 (w), 581 (w), 461 (w) cm–1
;
MS (ESI): m/z = 644 [M]+, 588, 544, 488, 470, 388, 259; HRMS (ESI):
m/z calcd. for C29H50N5O11+: 644.3493 [M]+, found 644.3501.
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Acknowledgments
Generous financial support by the Ministerium für Wissenschaft,
Forschung und Kunst des Landes Baden-Württemberg, the Carl-
Zeiss-Stiftung (Projecthouse NanoBioMater), the Forschungs-
fonds der Universität Stuttgart, the Baden-Württemberg-
Stiftung (project BioMat-S11 BiogelPlus) and the Alfred-Kärcher-
Stiftung are gratefully acknowledged. Open access funding
enabled and organized by Projekt DEAL.
[8]
Keywords: Amino acids · Biological activity · Click
chemistry · Triazoles · Triazolium
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© 2020 The Authors published by Wiley-VCH GmbH