Synthesis of a C-iminoribofuranoside analog of the nicotinamide phosphoribosyltransferase (NAMPT) inhibitor FK866

Article abstract of DOI:10.1002/hlca.201100415

FK866 (also named APO866 or WK175) is a potent NAMPT inhibitor being evaluated (Phase II) as a potential anticancer drug. The preparation of the C-iminoribofuranoside analog (2E)-N-[4-(1-benzoylpiperidin-4-yl)butyl]-3-{3- [(2S,3S,4R,5R)-3,4-dihydroxy-5-(h

Full text of DOI:10.1002/hlca.201100415

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Helvetica Chimica Acta – Vol. 95 (2012)
Synthesis of a C-Iminoribofuranoside Analog of the Nicotinamide
Phosphoribosyltransferase (NAMPT) Inhibitor FK866
by Annabelle Gillig, Somi Reddy Majjigapu, Bernard Sordat, and Pierre Vogel*
Laboratory of Glycochemistry and Asymmetric Synthesis (LGSA), Swiss Institute of Technology in
Lausanne (EPFL), Batochime, CH-1015 Lausanne
(phone: þ 41216939371; fax: þ 41216939375; e-mail: pierre.vogel@epfl.ch)
FK866 (also named APO866 or WK175) is a potent NAMPT inhibitor being evaluated (Phase II) as
a potential anticancer drug. The preparation of the C-iminoribofuranoside analog (2E)-N-[4-(1-
benzoylpiperidin-4-yl)butyl]-3-{3-[(2S,3S,4R,5R)-3,4-dihydroxy-5-(hydroxymethyl)pyrrolidin-2-yl]phe-
nyl}prop-2-enamide ((ꢀ)-1) is reported.
Introduction. – Proliferating cells have an increased demand of NADþ (nicotin-
amide adenine dinucleotide), the universal energy- and signal-carrying molecule [1].
Particularly, NADþ is involved in the transfer of ADP-ribosyl moiety to proteins, in the
calcium-signalling mechanism, in DNA repair, and it acts as a coenzyme of protein
deacetylases called sirtuins [2]. NADþ participates also in glycolysis and in oxidative
phosphorylation [3]. NADþ has several precursors [4]. One of them is nicotinamide
(NAM) [5] that is glycosylated by a-d-5-phosphoribosyl-1-pyrophosphate (PRPP) and
inorganic pyrophosphate (PPi) to NMN (nicotinamide mononucleotide) [6]. This
reversible reaction is catalyzed by nicotinamide phosphoribosyltransferase (NAMPT)
[7], an enzyme also called visfatin [8], and pre-B cell colony enhancing factor (PBEF),
which is a protein with multiple functional properties [9]. NAMPT is overexpressed in
cancer cells [10] and in proliferating cells [11]. NAMPT is probably involved in the
transformation of dormant form of tumors to malignant ones; it promotes the growth of
some types of tumors [9e]. Increased concentration of NAMPT has been reported in
colorectal [12], ovarian [13], and prostate [14] cancer. Thus, NAMPT represents an
attractive target for cancer chemotherapy. The best explored inhibitor of NAMPT is
FK866 (Fig. 1; also known as WK175 or APO866) [15]; it has an IC50 value of ca. 1 nm
for cytotoxicity toward several cancer cell lines. It also exhibits promising antitumor
activities against both solid tumors and leukemia in preclinical assays [16]. FK866
specifically inhibits human NADþ levels in tumors and ultimately induces apoptosis in
these cells [17][18]. FK866 enhances the resistivity of mammary carcinoma to radiation
[19].
FK866 has a chemosensitivity effect on leukemia cell death induced by antineuro-
plastin drug such as MNNG (1-methyl-3-nitro-1-nitrosoguanidinium) [20]. Synergistic
effects have also been noted for FK866 in combination with TRAIL (tumor necrosis
factor-related apoptosis-inducing ligand) [21] or with l-1-methyltryptophan (IDO-
specific inhibitor l-1 MT) [22]. FK866 is in Phase-II clinical trials against several forms
of human cancers.
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

Helvetica Chimica Acta – Vol. 95 (2012)
35
Fig. 1. Structures of NAMPT inhibitors
Secondary effects of the drug are lymphopenia, amenia, fatigue, and grade 3 nausea
(continuous 96 h infusion, every 28 d). The dose-limiting toxicity of FK866 is
thrombocytopenia [19]. This has led to the search for other NAMPT inhibitors such
as CHS-828 (Fig. 1; also named GMX1778) [23][24], which has been administrated
orally in Phase-I clinical trial (solid tumors). Toxicity was dominated by gastro-
intestinal symptoms and thrombocytopenia [25]. To improve pharmacokinetics and
water solubility, derivative EP1627 (also named GMX1777) was proposed as an
alternative to CHS-828 [26]. Similarly, the d-ribofuranosyl derivative of FK866, called
IS001, was prepared to improve poor water solubility of FK866. Unfortunately, IS001
has a weaker affinity to NAMPT than FK866. Crystal structures of IS001 complexed
with NAMPT showed that the aglycon part adopts the same position as FK866 alone in
the active site of dimeric NAMPT [27] (Fig. 2) [28][29]. In the latter complex, the site
reserved for the ribofuranosyl cation is free.
A novel NAMPT inhibitor, TRON-8, resulting from ꢂclick chemistryꢃ has been
shown to have an IC50 value of ca. 3 nm for NADþ depletion but is less cytotoxic than
FK866 [30]. Recently, CB30865 (also named MPI-0479626), a subnanomolar and
relative cytotoxic agent, was determined to inhibit human NAMPT with an IC50 value
of ca. 0.2 nm [31].
As mentioned above, although FK866 is a potent inhibitor of NAMPT (IC50 ca.
1 nm) and shows interesting key antitumor activities, its low bioavailability (96 h
continuous intravenous infusion) due to the metabolic instability of the pyridine moiety
[32] and toxicity toward lymphocytes [33] necessitates the search for analogs with a
better therapeutic index. In this report, we present our efforts toward this objective.
Inspired by the X-ray crystal structures reported for complexes of FK866 [28][29] and
IS001 [27] with NAMPT, we envisioned that the 1,4-dideoxy-1,4-imino-b-d-ribofur-

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Helvetica Chimica Acta – Vol. 95 (2012)
Fig. 2. Structure of FK866 and schematic representation of its interaction with NAMPT [28][29]
anosyl-C-aryl derivatives of IS001, compound (ꢀ)-1 (Fig. 3), should mimick the
transition state or a key intermediate formed in the rate-determining step of the
glycosidation process catalyzed by NAMPT, and thus be a good and selective inhibitor
of this enzyme. The X-ray structure of the NAMPTꢀIS001 complex suggested that the
iminoribitol moiety of (ꢀ)-1 should occupy the place reserved to the ribofuranosyl
cation on its way to be attached to the pyridine moiety of nicotinamide. The conjugate
acid (ammonium ion) of the iminoribitol moiety is expected to interact with the active
site of NAMPT, as does the d-ribofuranosyl cation intermediate. The observation that
IS001 was a weaker ligand than FK866 for NAMPT [27] is not a surprise to us. IS001 is
a product-like ligand, and, thus, NAMPT has been tuned up by Nature to remove it
from its active site. On the contrary, mimetic of IS001, (ꢀ)-1, is an intermediate or
transition state-like ligand, and thus should interact strongly with the enzyme.
Fig. 3. Structures of compounds (ꢀ)-1 and 2

Helvetica Chimica Acta – Vol. 95 (2012)
37
Results and Discussion. – Our synthesis of compound (ꢀ)-1 was inspired by the
synthesis of 2, developed by Schramm and co-workers in 1993 [34], and started from
1,4-dideoxy-1,4-imino-d-ribitol (3), prepared according to the procedure of Witte and
McClard [35]. The 2,3-cis-diol moiety of 3 was protected as an acetonide and the 5-OH
group as a silyl ether applying standard conditions (Scheme) to give 4 [36]. N-
Chlorination of 4 with N-chlorosuccinimide (NCS) and basic treatment afforded an
imine that reacted with (3-ethenylphenyl)magnesium bromide to afford the styrene
derivative (ꢀ)-5 (56%). The (1S)-configuration of (ꢀ)-5 was established by NOEs in its
2D-1H-NMR spectrum that showed correlation peaks HꢀC(4)/HꢀC(6) of the
pyrrolidine moiety and for the aromatic CꢀH and HꢀC(6a) pair. After protection of
amine (ꢀ)-5 as a N-Boc derivative (ꢀ)-6 (67%), metathesis with methyl acrylate
catalyzed by Grubbs-II catalyst provided (þ)-7 in 58% yield. Catalytic ((t-BuO)4Zr)
ester/amide exchange [37] with primary amino derivative 8 furnished acrylamide (ꢀ)-
9. Desilylation of (ꢀ)-9 with Bu4NF, followed by acidic hydrolysis of the carbamate and
acetonide moieties (i-PrOH/5n HCl), provided (ꢀ)-1 (quant.; Scheme). Compound 8
was prepared from commercially available 4-(piperidin-4-yl)butanoic acid, reduction
of which with LiAlH4 [38] gave the corresponding aminoalcohol, which was amidified
with PhCOCl [39]. Mitsunobu substitution with phthalimide [40] and subsequent
aminolysis of the phthalimide moiety with NH2NH2 · H2O [41] provided 8.
Scheme. Synthesis of C-Iminoribofuranoside Analog (ꢀ)-1 · HCl. For abbreviations, cf. the Exper. Part.
Conclusion. – An efficient synthesis of a C-iminoribofuranoside analog of the
NAMPT inhibitor FK866 has been developed. The method should allow generation of

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Helvetica Chimica Acta – Vol. 95 (2012)
a library of further analogs (e.g., acrylamides from (þ)-7). Their syntheses will be
reported together with their biological activities in a forthcoming article.
Experimental Part
General. All commercially available reagents and solvents (Fluka, Aldrich, Acros) were used
without further purification. For reactions requiring anh. conditions, dry solvents were bought (Fluka,
Aldrich). Reactions were monitored by TLC (Merck; silica gel 60 F254 plates); detection with UV light,
KMnO4 , or Pancaldi reagent ((NH4)6MoO4 , Ce(SO4)2 , H2SO4, H2O). Purifications used flash
chromatography (FC) on silica gel (SiO2; Merck No. 9385 silica gel 60, 240 – 400 mesh). Optical
rotations: at 258 with a Jasco P-1020 polarimeter; [a] values in 10ꢀ1 deg cm2 gꢀ1. UV Spectra: Perkin-
Elmer Lambda 10 UV/VIS spectrophotometer. IR Spectra: Perkin-Elmer Paragon 1000 FT-IR
1
spectrometer. H-NMR Spectra: Bruker ARX-400 and a DPY-400 spectrometer at 400 MHz; chemical
shifts in ppm rel. to residual 1H-solvent signal (CHD2OD: d(H) 3.34 ppm; CHCl3: d(H) 7.27 ppm;
C6HD5: d(H) 7.30 ppm) as the internal reference; assignments confirmed by 2D-COSY spectra; the
multiplicities reflect apparent signal patterns; 13C-NMR spectra: with the same instrument as above at
100.6 MHz; chemical shifts in ppm rel. to residual 13C-solvent signal (CD3OD: d(C) 49 ppm; CDCl3:
d(C) 77 ppm; C6D6: d(C) 128.5 ppm); assignments confirmed by 2D-HSQC spectra; coupling constants
J(H,H), J(C,H) in Hz. MALDI-TOF-MS: Axima-CFRþ spectrometer, Kratos. ESI-Q-MS: Finnigan SSQ
710C spectrometer, Thermoquest. ESI-HR-MS: Q-TOF Ultima spectrometer, Microman. Elemental
analyses: performed by Mr. Euro Solari, EPFL. Abbreviations. Boc, (tert-Butoxy)carbonyl; DMAP, 4-
(dimethylamino)pyridine; HOAt, 1-hydroxy-7-azabenzotriazole; NCS, N-chlorosuccinimide; TBAF,
Bu4NF; TBSOTf, (tert-butyl)dimethylsilyl triflate (¼trifluoromethanesulfonate); TsOH, p-toluenesul-
fonic acid.
5-O-[(tert-Butyl)dimethylsilyl]-1,4-dideoxy-1,4-imino-2,3-O-isopropylidene-d-ribitol (¼(3aR,
4R,6aS)-4-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)tetrahydro-2,2-dimethyl-3aH-[1,3]dioxolo[4,5-c]-
pyrrole; 4). To a stirred suspension of 1,4-dideoxy-1,4-imino-d-ribitol (3; 5 g, 37.5 mmol) in 70 ml of DMF
was added 30 ml of 2,2-dimethoxypropane and 2 g of TsOH as granula. After 3 h at 208, TsOH granula
was filtered, the mixture was concentrated (508 water bath), and the crude product was dissolved in dry
CH2Cl2 (150 ml). TBSOTf (25 ml, 100 mmol) and 1H-imidazole (7 g, 100 mmol) were added. The
mixture was stirred 12 h and washed with a sat. aq. soln. of NaHCO3 (250 ml) and brine (250 ml), dried
(MgSO4), and concentrated. Purification by FC (SiO2; 10 to 100% AcOEt in petroleum ether (PE)
containing 0.03% of Et3N) provided 4 (7.9 g, 69%). Yellow oil. Data were in accordance with those
published in [36].
(3aR,4R,6S,6aS)-4-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)-6-(3-ethenylphenyl)tetrahydro-2,2-di-
methyl-3aH-[1,3]dioxolo[4,5-c]pyrrole ((ꢀ)-5). Compound 4 (2.3 g, 7.8 mmol) was dissolved in pentane
(112 ml), and NCS (4.2 g, 31.3 mmol) was added at 208. The mixture was stirred for 30 min, filtered, and
solvents were evaporated. The crude product was dissolved in dry THF (50 ml), and a soln. of lithium
2,2,6,6-tetramethylpiperidide (1.2 equiv., prepared previously with 2,2,6,6-tetramethylpiperidine (1.7 ml,
9.8 mmol) and BuLi (1.6m in hexane, 5.9 ml, 9.4 mmol) in dry THF (62.5 ml)) was added dropwise over
3 h at ꢀ 788. The mixture was stirred for 2 h at ꢀ 788 and concentrated. The crude product was dissolved
in dry THF (112.5 ml), and (3-ethenylphenyl)magnesium bromide (0.28m, 116.6 ml, 62.6 mmol) was
added dropwise during 1 h at ꢀ 788. The mixture was stirred for 3 h at ꢀ 788 and 12 h at 08, then, 500 ml
of Et2O were added, followed by 200 ml of a 5% aq. soln. of NH4Cl. The org. phase was sequentially
washed with H2O (500 ml) and brine (500 ml), dried (MgSO4), and solvents were evaporated.
Purification by FC (SiO2; 5% AcOEt in PE) provided (ꢀ)-5 (1.7 g, 56%). Yellow oil. [a]2D5 ¼ ꢀ13,
25
25
25
[a] ¼ ꢀ13, [a] ¼ ꢀ25, [a] ¼ ꢀ39 (c ¼ 0.10 g/100 ml, MeCN). UV (MeCN): 246 (8820). IR (neat):
577
435
405
1
2955, 2925, 2855, 1380, 1370, 1255, 1070, 835, 630. H-NMR (400 MHz, CDCl3): 7.46, 7.27 (2m, 4 arom.
H); 6.72 (dd, 3J(1’’,2’’) ¼ 10.8, 3J(1’’,2’’) ¼ 17.6, HꢀC(1’’)); 5.76 (dd, 3J(2’’,1’’) ¼ 17.6, 2J(2’’,2’’) ¼ 0.9,
a
b
b
b
a
3
2
3
3
HbꢀC(2’’)); 5.25 (dd, J(2’’,1’’) ¼ 10.8, J(2’’,2’’) ¼ 0.9, HaꢀC(2’’)); 4.51 (dd, J(3a,6a) ¼ 7.1, J(3a,4) ¼ 4.7,
a
a
b
HꢀC(3a)); 4.45 (dd, 3J(6a,3a) ¼ 7.1, 3J(6a,6)) ¼ 5.3, HꢀC(6a)); 4.19 (d, 3J(6,6a) ¼ 5.3, HꢀC(6)); 3.88 (dd,
2J(1a’,1b’) ¼ 10.2, 3J(1a’,4) ¼ 3.7, HaꢀC(1’)); 3.78 (dd, 2J(1b’,1a’) ¼ 10.2, 3J(1b’,4) ¼ 5.3, HbꢀC(1’)); 3.35 (ddd,

Helvetica Chimica Acta – Vol. 95 (2012)
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3
3
3J(4,1b’) ¼ 5.3, J(4,3a) ¼ 4.7, J(4,1a’) ¼ 3.7, HꢀC(4)); 1.59, 1.34 (2s, Me2C); 0.91 (s, t-Bu); 0.10, 0.09 (2s,
Me2Si). 13C-NMR (100.6 MHz, CDCl3): 141.6; 137.8; 136.7; 128.7; 126.1; 125.2; 124.4; 114.1; 114.0; 87.6;
81.2; 67.9; 65.6; 63.7; 29.7; 27.5; 25.4; 25.9; ꢀ 5.5. HR-ESI-TOF-MS: 390.2451 ([M þ H]þ, C22H36NO3Siþ;
calc. 390.2464).
tert-Butyl (3aR,4R,6S,6aS)-4-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)-6-(3-ethenylphenyl)tetra-
hydro-2,2-dimethyl-5H-[1,3]dioxolo[4,5-c]pyrrole-5-carboxylate ((ꢀ)-6). Di(tert-butyl) dicarbonate
(2 g, 8.46 mmol) and DMAP (1.7 g, 460.6 mmol) were dissolved in dry CH2Cl2 (10 ml) at r.t. for 5 min.
Then, (ꢀ)-5 (1.7 g, 4.4 mmol) was added, followed by pyridine (3 ml) in dry CH2Cl2 (20 ml). The mixture
was stirred for 12 h. Et2O (20 ml) was then added, and the org. layer was washed with a 5% aq. soln. of
NH4Cl (20 ml), dried (MgSO4), filtered, and concentrated in vacuo. Purification by FC (SiO2; 2%
25
25
25
AcOEt in PE) provided (ꢀ)-6 (1.3 g, 60%). Yellow oil. [a]2D5 ¼ ꢀ30, [a] ¼ ꢀ37, [a] ¼ ꢀ57, [a]
¼
577
435
405
ꢀ60 (c ¼ 0.03 g/100 ml, MeCN). UV (MeCN): 205 (600), 285 (890), 250 (14’000). IR (neat): 2955, 2930,
1695, 1365, 1250, 1065, 835, 775. 1H-NMR (400 MHz, CDCl3): 7.28 (m, 4 arom. H); 6.71 (dd, 3J(1’’,2’’) ¼
a
17.6, 3J(1’’,2’’) ¼ 10.9, HꢀC(1’’)); 5.72 (dd, 3J(2’’,1’’) ¼ 17.6, 3J(2’’,2’’) ¼ 0.8, HaꢀC(2’’)); 5.23 (dd, 3J(2’’,1’’) ¼
b
a
a
b
b
10.9, 3J(2’’,2’’) ¼ 0.8, HbꢀC(2’’)); 5.00 (m, HꢀC(6)); 4.70 (d, 3J(6a,6) ¼ 5.6, HꢀC(6a)); 4.64 (dd,
b
a
3J(3a,6a) ¼ 5.6, HꢀC(3a)); 4.26 (m, HꢀC(4)); 3.88 (m, CH2(1’)); 1.58, 1.37 (2s, Me2C); 1.37 (br. s,
CO2CMe3); 0.86 (s, t-Bu); 0.07, 0.04 (2s, Me2Si). 13C-NMR (100.6 MHz, CDCl3): 154.7; 136.9; 136.6;
128.4; 125.7; 125.3; 124.6; 124.0; 113.7; 87.2; 81.4; 80.0; 69.3; 65.3; 63.1; 28.1; 27.8; 18.3; 25.8; 25.6; ꢀ 5.5.
HR-ESI-TOF-MS: 490.3007 ([M þ H]þ, C27H44NO5Siþ; calc. 490.4877). Anal. calc. for C27H43NO5Si
(489.72): C 66.22, H 8.85, N 2.86; found: C 66.46, H 8.95, N 2.73.
tert-Butyl (3aR,4R,6S,6aS)-4-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)tetrahydro-6-{3-[(1E)-3-
methoxy-3-oxoprop-1-en-1-yl]phenyl}-2,2-dimethyl-5H-[1,3]dioxolo[4,5-c]pyrrole-5-carboxylate ((þ)-
7). A soln. of (ꢀ)-6 (887 mg, 1.8 mmol) in dry CH2Cl2 (1.8 ml) and methyl acrylate (312 mg, 3.6 mmol)
were added to a soln. of HoveydaꢀGrubbs second-generation catalyst (113 mg, 0.2 mmol) in dry CH2Cl2
(7.2 ml) under Ar. The mixture was stirred for 20 h at r.t., and solvents were evaporated. Purification by
FC (SiO2; 4 to 6% AcOEt in PE) provided the starting material (ꢀ)-6 (127.2 mg, 14%) and the desired
25
25
25
cross product (þ)-7 (561.3 mg, 58%). Yellow oil. [a]2D5 ¼ þ33, [a] ¼ ꢀ30, [a] ¼ ꢀ75, [a] ¼ ꢀ91
577
435
405
(c ¼ 0.10 g/100 ml, MeCN). UV (MeCN): 278 (18’800). IR (neat): 2930, 1720, 1695, 1375, 1170, 1065, 835,
775. 1H-NMR (400 MHz, CDCl3): 7.67 (d, , 3J(1’’,2’’) ¼ 16.0, HꢀC(1’’)); 7.55 – 7.27 (m, 4 arom. H); 6.41 (d,
3J(2’’,1’’) ¼ 16.0, HꢀC(2’’)); 5.14 – 4.69 (m, HꢀC(6)); 4.65 (d, 3J ¼ 5.5, HꢀC(6a)); 4.57 (m, HꢀC(3a)); 4.21
(br. s, HꢀC(4)); 4.06 – 3.61 (m, CH2(1’)); 3.79 (s, MeO); 1.58, 1.34 (2s, Me2C); 1.28 – 1.12 (m, CO2CMe3);
0.8 (s, t-Bu); 0.02, 0.01 (2s, Me2Si). 13C-NMR (100.6 MHz, CDCl3): 167.4; 154.6; 144.9; 143.1; 134.3; 128.8;
127.8; 126.5; 125.7; 117.7; 112.0; 87.0; 81.4; 80.0; 69.3; 65.2; 63.3; 51.6; 29.7; 28.1; 25.8; 25.6; ꢀ 5.5. HR-
ESI-TOF-MS: 548.3028 ([M þ H]þ, C29H46NO7Siþ; calc. 548.3044). Anal. calc. for C29H45NO7Si · 0.33
hexane: C 64.59, H 8.68, N 2.43; found: C 64.45, H 8.95, N 2.17.
[4-(4-Aminobutyl)piperidin-1-yl](phenyl)methanone (8). A suspension of 4-(piperidin-4-yl)buta-
noic acid hydrochloride (9 g; 43 mmol) in dry THF (250 ml) was cooled in an ice bath and stirred during
the dropwise addition of LiAlH4 (6.6 g; 173 mmol). Stirring was continued at 208 for 10 min, and the
mixture was heated under reflux for 6 h. The mixture was cooled to 08, and 40% aq. KOH was added
slowly under vigorous stirring. After stirring at 208 for 1 h, the suspension was filtered on a Celite pad that
was washed with THF (150 ml) and MeOH (150 ml). After evaporation of the solvent, the crude was
purified by FC (SiO2; AcOEt/Et3N/MeOH 18 :2 :80) to give 77% of the reduced product as a yellow oil.
Under Ar, Et3N (1.79 ml; 12.7 mmol) and PhCOCl (0.74 ml; 6.36 mmol) were subsequently added to a
cooled (08) soln. of the previously reduced compound (1 g, 6.36 mmol) in dry CH2Cl2 (20 ml), and the
mixture was stirred for 10 min. After stirring at 208 for 2 h, the mixture was diluted with a sat. aq. soln. of
NH4Cl until a clear soln. was obtained. It was then extracted with CH2Cl2 (3 ꢁ 50 ml). The combined org.
extracts were washed with brine (100 ml), dried (MgSO4), and the solvents were evaporated. Purification
by FC (SiO2; AcOEt/PE 7:3) gave 1.32 g of the protected product (80%) as a light yellow oil. Under Ar,
diethyl azodicarboxylate (243 ml; 1.3 mmol) was added dropwise to a soln. of the previous protected
compound (1.34 g; 5 mmol), phthalimide (840 mg; 5 mmol), and Ph3P (1.4 g; 5 mmol) in THF (15 ml) at
208. After 1 h, the mixture was concentrated. Purification by FC (85% Et2O in PE) afforded 2-{4-[1-
(phenylcarbonyl)piperidin-4-yl]butyl}-1H-isoindole-1,3(2H)dione (1.87 g; 91%). White solid. M.p. 96 –
1
1008. IR (neat): 2930, 1705, 1625, 1394, 708. H-NMR (400 MHz, 323 K, CDCl3): 7.96, 7.75 (2m, 4 H,

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Helvetica Chimica Acta – Vol. 95 (2012)
phthalimido); 7.33 (m, 5 arom. H); 4.68, 3.70 (2 br. m, HaꢀC(2’’,6’’)); 3.70 (m, HbꢀC(2’’,6’’), CH2(1’));
2.95, 2.73 (2 br. t, CH2(3’’,5’’)); 1.86 – 1.00 (m, CH2(2’), CH2(3’), CH2(4’), HꢀC(4’’)). 13C-NMR
(100.6 MHz, CDCl3): 170.2; 168.4; 136.4; 133.9; 132.0; 129.3; 128.3; 126.8; 123.1; 62.1; 48.0; 37.8; 36.0;
35.8; 28.7; 23.8. HR-ESI-TOF-MS: 391.2004 ([M þ H]þ, C24H27N2O3þ ; calc. 391.2022).
Under Ar, NH2NH2 · H2O (0.51 ml; 10.38 mmol) was added to a soln. of the above product (1.6 g;
4.15 mmol) in dry EtOH (50 ml), and the mixture was stirred at 208 for 10 min and then heated under
reflux for 2 h. The mixture was filtered over Celite, and the solvents were evaporated. The crude product
was dissolved in CH2Cl2 (100 ml), and the soln. was washed with an aq. soln. of K2CO3 (100 ml). The aq.
layer was extracted with CH2Cl2 (3 ꢁ 50 ml), and the combined org. extracts were washed with brine,
dried (MgSO4), filtered, and solvents were evaporated. Purification by FC (SiO2; MeOH/AcOEt/Et3N
80 :18 :2) afforded 760 mg (70%) of 8. Yellow oil. IR (neat): 2919, 1623, 1430, 1276, 707. 1H-NMR
(400 MHz, 323K, CDCl3): 7.45 – 7.33 (m, 5 arom. H); 4.68, 3.72 (2m, 2 HaꢀC(2)); 2.96 (m, HbꢀC(2)); 2.71
(m, HbꢀC(2), CH2(4’)); 1.90 (br. s, NH2); 1.81, 1.63 (2m, 2 HaꢀC(3)); 1.57 – 1.42 (m, HꢀC(4), CH2(3’));
1.40 – 1.24 (m, CH2(1’), CH2(2’)); 1.20, 1.11 (2m, 2 HbꢀC(3)). 13C-NMR (100.6 MHz, CDCl3): 170.2;
136.3; 129.4; 128.4; 126.7; 48.0; 41.2; 36.0; 35.9; 32.8; 31.7; 23.7. HR-ESI-TOF-MS: 261.1975 ([M þ H]þ,
C16H25N2Oþ; calc. 261.1967. Anal. calc. for C16H24N2O · 0.5 H2O: C 71.34, H 9.35, N 10.40; found: C 70.96,
H 9.22, N 10.61.
tert-Butyl (3aS,4S,6R,6aR)-4-{3-[(1E)-3-{[4-(1-Benzoylpiperidin-4-yl)butyl]amino}-3-oxoprop-1-
en-1-yl]phenyl}-6-({[(tert-butyl)(dimethyl)silyl]oxy}methyl)tetrahydro-2,2-dimethyl-5H-[1,3]dioxo-
lo[4,5-c]pyrrole-5-carboxylate ((ꢀ)-9). To a soln of 8 (92.2 mg, 354 mmol) in dry toluene (550 ml), (þ)-7
(135 mg, 246.5 mmol) and HOAt (7 mg, 55 mmol) were added, followed by the addition of (t-BuO)4Zr
(21 ml, 55 mmol) under Ar. The mixture was stirred at 1008 for 12 h and cooled down to r.t. MeOH (1 ml)
and CH2Cl2 (1 ml) were added, and the soln. was filtered through SiO2. Solvents were evaporated, and
the residue was purified by FC (SiO2; 50% AcOEt in PE) to afford (ꢀ)-9 (116 mg, 60%). White foam.
25
25
25
[a]2D5 ¼ ꢀ9.5, [a] ¼ ꢀ21, [a] ¼ ꢀ34, [a] ¼ ꢀ53 (c ¼ 0.052 g/100 ml, MeCN). UV (MeCN): 271
577
435
405
1
(26’800). IR (neat): 3300, 2925, 1695, 1610, 1365, 1260, 1065, 800. H-NMR (400 MHz, 323 K, CDCl3):
7.58 (d, 3J(1’’,2’’) ¼ 15.6, HꢀC(1’’)); 7.41 – 7.27 (m, 9 arom. H); 6.34 (d, 3J(2’’,1’’) ¼ 15.6, HꢀC(2’’)); 5.63 (m,
NH); 4.90 (m, HꢀC(4)); 4.67 (d, 3J ¼ 5.5, HꢀC(3a)); 4.60 (dd, 3J ¼ 5.5, 3.2, HꢀC(6a)); 4.25 (m, HꢀC(6));
3.85 (m, CH2(1’)); 3.37 (dd, 3J ¼ 6.9, 13.1, NHCH2); 2.85, 1.72 (2m, (CH2)2NCO); 1.58, 1.35 (2s, Me2C);
1.62 – 1.06 (m, CO2CMe3, NHCH2CH2CH2CH2CH(CH2)2); 0.84 (s, t-Bu); 0.04, 0.02 (2s, Me2Si).
13C-NMR (100.6 MHz, CDCl3): 170.1; 165.8; 154.5; 140.4; 136.2; 129.3; 128.3; 126.6; 126.0; 125.4; 120.8;
111.8; 87.0; 81.2; 79.9; 69.2; 65.0; 63.0; 47.9; 39.4; 35.9; 31.8; 29.7; 23.8; 32.7; 27.9; 25.7; 25.5; 18.1; ꢀ 5.6.
HR-ESI-TOF-MS: 776.4665 ([M þ H]þ, C44H66N3O7Siþ; calc. 776.4670). Anal. calc. for C44H65N3O7Si: C
68.09, H 8.44, N 5.41, found: C 67.97, H 8.34, N 5.37.
tert-Butyl (3aS,4S,6R,6aR)-4-{3-[(1E)-3-{[4-(1-Benzoylpiperidin-4-yl)butyl]amino}-3-oxoprop-1-
en-1-yl]phenyl}tetrahydro-6-(hydroxymethyl)-2,2-dimethyl-5H-[1,3]dioxolo[4,5-c]pyrrole-5-carboxylate
((ꢀ)-10). TBAF (1m in THF, 193 ml, 193 mmol) was added dropwise to a soln. of (ꢀ)-9 (83.3 mg,
107.3 mmol) in THF (550 ml). The mixture was stirred for 1 h at r.t., and MeOH (550 ml) was added.
Solvents were evaporated, and the residue was purified by FC (SiO2; 60 to 100% AcOEt in PE) to afford
25
25
25
(ꢀ)-10 (65.3 mg, 92%). Light pink solid. M.p. 98 – 1048. [a]2D5 ¼ ꢀ8, [a] ¼ 0, [a] ¼ ꢀ10, [a] ¼ ꢀ17
577
435
405
(c ¼ 0.052 g/100 ml, MeCN). UV (MeCN): 271 (14’900). IR (neat): 2925, 1610, 1260, 1015, 790. 1H-NMR
(400 MHz, 323 K, CDCl3): 7.56 (d, 3J(1’,2’) ¼ 15.6, HꢀC(1’)); 7.50 – 7.23 (2m, 9 arom. H); 6.40 (d,
3J(2’,1’) ¼ 15.6, HꢀC(2’)); 6.01 (br. s, NH); 4.98 (m, HꢀC(4)); 4.62 – 4.51 (2m, HꢀC(3a), HꢀC(6a)); 4.29
3
(m, HꢀC(6)); 3.87, 3.74 (2dd, CH2OH); 3.34 (dd, J ¼ 6.7, 12.5, NHCH2); 2.86, 1.65 (2m, (CH2)2NCO);
1.57, 1.32 (2s, Me2C); 1.56 – 1.06 (m, CO2CMe3, NHCH2CH2CH2CH2CH(CH2)2). 13C-NMR (100.6 MHz,
CDCl3): 170.3; 165.9; 155.8; 142.0; 140.4; 136.2; 135.1; 129.4; 128.9; 128.3; 127.0; 126.7; 124.4; 121.1;
112.2; 86.6; 81.2; 80.8; 68.7; 65.9; 64.2; 42.5; 39.5; 35.9; 32.8; 31.9; 29.8; 29.6; 23.9; 28.0; 27.5; 25.4. HR-
ESI-TOF-MS: 662.3802 ([M þ H]þ, C38H52N3Oþ7 ; calc. 662.3805). Anal. calc. for C38H51N3O7 · H2O: C
67.13, H 7.86, N 6.18; found: C 67.42, H 7.92, N 5.94.
(2E)-N-[4-(1-Benzoylpiperidin-4-yl)butyl]-3-{3-[(2S,3S,4R,5R)-3,4-dihydroxy-5-(hydroxymethyl)-
pyrrolidin-2-yl]phenyl}prop-2-enamide Hydrochloride ((ꢀ)-1 · HCl). To a soln. of (ꢀ)-10 (53 mg,
80 mmol) in i-PrOH (1 ml) was added a 5n soln. of HCl in i-PrOH (800 ml) dropwise. The mixture was
stirred at 208 for 24 h, and the solvents were evaporated to afford (ꢀ)-1 · HCl (42 mg, 94%). White solid.

Helvetica Chimica Acta – Vol. 95 (2012)
41
1
3
M.p. 104 – 1078. H-NMR (400 MHz, CD3OD): 7.83 – 7.32 (m, 10 arom. H, CONH), 7.55 (d, J(1’,2’) ¼
15.8, HꢀC(1’)); 6.69 (d, 3J(2’,1’) ¼ 15.8, HꢀC(2’)); 4.70 – 4.48 (m, HꢀC(2), HꢀC(3)); 4.59, 2.83 (2m,
NHCH2); 4.27 (m, HꢀC(4)); 3.92 (m, CH2OH), 3.70 (m, HꢀC(5)); 3.70, 3.11, 1.86, 1.69 (4m,
(CH2)2NCO); 1.65 – 1.06 (m, NHCH2CH2CH2CH2CH(CH2)2). 13C-NMR (100.6 MHz, CD3OD): 172.3;
168.2; 140.5; 137.3; 137.1; 135.2; 131.0; 130.9; 130.8; 129.7; 129.6; 129.2; 127.8; 123.3; 112.2; 76.1; 73.1; 67.8;
65.5; 60.2; 49.0; 43.8; 40.5; 37.1; 33.9; 30.1; 25.2; 25.0. HR-ESI-TOF-MS: 522.2960 ([M þ H]þ,
C30H40N3Oþ5 ; calc. 522.2968). Anal. calc. for C30H39N3O5 · HCl · 1.5 H2O: C 61.58, H 7.41, N 7.18; found: C
61.84, H 7.27, N 6.88.
This work was supported by the Swiss National Science Foundation and by the European FP7
Heath.2010.2.4.1-6 Project PANACREAS. We are grateful also to Dr. L. Menin and M. F. Sepulveda for
the mass spectra, and to M. M. Rey for technical assistance.
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Received October 26, 2011