10.35 (1 H, br s); δC(CDCl3) 22.8 (q), 28.1 (q), 28.3 (q), 42.3 (t),
49.2 (d), 80.4 (s), 127.8 (d), 128.6 (d), 130.2 (s), 131.5 (d), 132.0
(d), 132.6 (s), 157.0 (s), 166.5 (s), 167.4 (s), 173.3 (s); m/z 392
(Mϩ) (Found: C, 56.73; H, 6.83; N, 9.93. C19H25N3O6ؒ0.75H2O
requires C, 56.36; H, 6.54; N, 10.38%).
and concentrated to a clear oil. Chromatography over silica gel
(3 : 2 ethyl acetate–hexanes) gave a clear, colorless foam of 16
(86 mg, 50%); νmax(CHCl3)/cmϪ1 3200, 2960, 1726, 1610, 1125;
δH(CDCl3) 1.29 (9 H, s), 1.48 (9 H, s), 1.97 (3 H, s), 3.40 (2 H,
m), 3.65 (1 H, m), 4.68 (2 H, d, J 6), 5.25 (2 H, dd, J 11, 25),
5.80–6.00 (1 H, m), 6.23 (1 H, d, J 10), 7.38–7.57 (3 H, m), 8.00
(2 H, d, J 7), 9.60 (1 H, br s), 11.30 (1 H, s); δC(CDCl3) 22.8 (q),
26.8 (q), 26.9 (q), 27.0 (q), 40.8 (t), 48.6 (d), 65.0 (t), 83.0 (s),
117.2 (t), 127.0 (d), 127.4 (d), 128.4 (d), 129.3 (s), 130.2 (d),
131.9 (d), 132.2 (s), 151.4 (s), 154.3 (s), 162.8 (s), 165.9 (s), 170.2
(s); m/z 574 (Mϩ) (Found: C, 58.74; H, 6.80; N, 12.35.
C28H39N5O8 requires C, 58.63; H, 6.85; N, 12.21%).
Azlactone of (2Z,4RS)-5-acetamido-4-amino-2-benzamidopent-
2-enoic acid (TFA salt) 14
To a solution of 13 (30 mg, 0.08 mmol) in CH2Cl2 (2 cm3) at
0 ЊC was added triethylsilane (0.025 cm3, 0.16 mmol). The
mixture was stirred for 5 min and TFA (1.0 cm3, 12.98 mmol)
was added. The solution was brought to room temperature and
stirred for 1 h. The solvent was evaporated to give a residue
which was concentrated further with acetonitrile (2 × cm3). The
resulting foam was suspended in ethyl acetate–diethyl ether
(1 : 1) and filtered to give a tan amorphous resin of 14 (18 mg,
86%); νmax(KBr)/cmϪ1 3400, 3000, 1671, 1202; δH(DMSO-d6)
1.81 (3 H, s), 3.20–3.40 (2 H, m), 4.10 (1 H, m), 6.28 (1 H, d,
J 9), 7.50–7.65 (3 H, m), 7.91 (2 H, d, J 8), 8.13 (1 H, t, J 6);
δC(DMSO-d6) 22.5 (q), 40.3 (t), 47.9 (d), 127.7 (d), 128.1 (s),
128.4 (d), 128.7 (d), 132.0 (d), 132.7 (s), 133.2 (s), 164.8 (s),
166.1 (s), 170.5 (s); m/z 274 (Mϩ, free base) (Found: C, 46.85; H,
4.88; N, 9.88. C14H15N3O3ؒCF3COOHؒ1.25H2O requires C,
46.89; H, 5.00; N, 10.25%).
(2Z,4RS)-5-Acetamido-4-guanidino-2-benzamidopent-2-enoic
acid (sodium salt) 5
A mixture of 16 (75 mg, 0.13 mmol) and TFA (2 cm 3, 26 mmol)
was stirred at room temperature for 3 h. The solution was
diluted to 5 cm3 with acetonitrile, evaporated, and concentrated
again from acetonitrile (2 × 5 cm3). The resulting amorphous
foam was the monotrifluoroacetate salt of the deprotected
guanidino allyl ester (66 mg, 100%); νmax(CHCl3)/cmϪ1 3350,
2975, 1674, 1280, 1230; δH(DMSO-d6) 1.75 (3 H, s), 3.15–3.35
(2 H, m), 4.51 (1 H, m), 4.66 (2 H, d, J 6), 5.26 (2 H, dd, J 9, 22),
5.80–5.97 (1 H, m), 6.47 (1 H, d, J 6), 7.20 (3 H, br s), 7.50 (3 H,
m), 7.76 (1 H, d, J 6), 7.95 (2 H, d, J 7), 8.14 (1 H, t, J 5), 9.87
(1 H, s). To a solution of the above monotrifluoroacetate salt
(59 mg, 0.12 mmol) in CH2Cl2 (1 cm3) under N2 was added a
solution of sodium 2-ethylhexanoate (42 mg, 0.25 mmol) in
ethyl acetate (2 cm3). To the solution was then added triphenyl-
phosphine (1 mg, 0.004 mmol) and tetrakis(triphenylphos-
phine)palladium(0) (3.5 mg, 0.003 mmol). The clear yellow
solution was stirred for 1 h at room temperature at which point
a crystalline solid appeared. The mixture was stirred for 16 h
and the suspension was sonicated for 30 min. The mixture was
then centrifuged and decanted. The solid was treated with
diethyl ether (3.5 cm3), centrifuged, and decanted to give 5 (39
mg, 91%). A pure sample was prepared by recrystallization
from acetonitrile–methanol–diethyl ether; mp 192–198 ЊC;
δH(DMSO-d6) 1.78 (3 H, s), 3.00–3.30 (2 H, m), 4.40 (1 H, m),
6.10 (1 H, d, J 6), 7.56 (3 H, m), 7.80–8.15 (4 H, br m), 7.92
(2 H, d, J 7), 8.10 (1 H, m), 9.00 (1 H, br s), 9.40 (1 H, br s);
δC(DMSO-d6) 22.4 (q), 42.1 (t), 56.0 (d), 127.2 (d), 128.2 (d),
128.4 (s), 128.5 (s), 130.3 (d), 131.2 (d), 159.6 (s), 166.3 (s), 169.8
(s), 172.0 (s); HRMS found MHϩ 334.1513. C15H20N5O4
requires 334.1515.
Allyl (2Z,4RS)-5-acetamido-4-(N-tert-butoxycarbonylamino)-2-
benzamidopent-2-enoate 15
A mixture of 13 (188 mg, 0.48 mmol), potassium carbonate (75
mg, 0.54 mmol), and allyl bromide (0.06 cm3, 0.69 mmol) in
DMF (2 cm3) was stirred at room temperature for 1 h. The
mixture was partitioned between ethyl acetate (30 cm3) and
brine (2 × 30 cm3). The organic layer was dried (Na2SO4) and
evaporated. The residue was chromatographed over silica gel
(3 : 2 ethyl acetate–hexanes) to give a white foam of 15 (144 mg,
70%); νmax(CHCl3)/cmϪ1 3300, 1669, 1510, 1368, 1160; δH
(CDCl3) 1.44 (9 H, s), 2.04 (3 H, s), 3.40–3.60 (2 H, m), 4.40
(1 H, m), 4.71 (2 H, d, J 6), 5.28 (2 H, dd, J 9, 21), 5.95 (1 H, m),
6.20 (2 H, m), 6.62 (1 H, m), 7.53 (3 H, m), 8.01 (2 H, d, J 8),
10.10 (1 H, br s); δC(CDCl3) 22.8 (q), 28.1 (q), 28.3 (q), 42.4 (t),
49.5 (d), 66.2 (t), 80.4 (s), 118.5 (t), 127.7 (d), 128.5 (d), 128.7
(d), 130.7 (s), 131.7 (d), 132.2 (d), 132.8 (s), 155.9 (s), 164.2 (s),
166.4 (s), 172.8 (s); m/z 431 (Mϩ) (Found: C, 61.41; H, 6.98; N,
9.71. C22H29N3O6 requires C, 61.24; H, 6.77; N, 9.74%).
Allyl (2Z,4RS)-5-acetamido-4-[NЈ,NЉ-bis(tert-butoxycarbonyl)-
guanidino]-2-benzamidopent-2-enoate 16
Acknowledgements
To a solution of 15 (130 mg, 0.30 mmol) in CH2Cl2 (1 cm3) at
0 ЊC under N2 was added triethylsilane (0.08 cm3, 0.50 mmol).
The solution was stirred for 2 min and TFA (1 cm3, 13.00
mmol) was added. The mixture was stirred for 1 h as it was
gradually brought to room temperature, diluted to 5 cm3 with
acetonitrile, and evaporated. The residue was evaporated
further with acetonitrile (2 × 5 cm3) to give an oil of the 4-(RS)-
deprotected amine trifluoroacetate salt intermediate, used as
such without further purification for the subsequent step;
νmax(KBr)/cmϪ1 3600, 3000, 1668, 1180; δH(DMSO-d6) 1.80
(3 H, s), 3.25–3.35 (2 H, m), 4.20 (1 H, m), 4.62 (2 H, m), 4.80
(1 H, m), 5.40 (2 H, dd, J 9, 21), 6.00 (1 H, m), 6.35 (1 H, d, J 5),
7.55 (3 H, m), 7.72 (2 H, d, J 8), 8.36 (1 H, t, J 6); m/z 331 (Mϩ,
free base). The oil thus obtained (133 mg, 0.30 mmol) was dis-
solved in DMF (2.5 cm3) under N2 at 0 ЊC and triethylamine
(0.13 cm3, 0.93 mmol) was added. The solution was stirred for
2 min and N,N Ј-bis(Boc)-S-methylisothiourea (87 mg, 0.30
mmol) and mercuric chloride (81 mg, 0.30 mmol) were added.
The mixture was brought to room temperature and stirred for
2 h, the suspension was diluted with ethyl acetate (10 cm3), and
filtered through a pad of Celite (sintered glass funnel). The
filtrate was extracted with brine (2 × 30 cm3), dried (Na2SO4),
The authors thank Joe Tang for development of the neuramini-
dase fluorescent assay. We also thank Jonathan Paschal and
Larry Spangle for NOE studies, along with the Physical Chem-
istry Department at Eli Lilly and Company for spectral data.
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