Synthesis of conformationally constrained diaminodicarboxylic acid derivatives

Article abstract of DOI:10.1021/jo901892d

(Chemical Presented) Functionally protected forms of three conformationally constrained diaminodicarboxylic acids were synthesized and characterized. 2,2′-Diaminospiro[3.3]heptane-2,2′-dicarboxylic acid, an analogue of diaminopimelic acid, was prepared in

Full text of DOI:10.1021/jo901892d

pubs.acs.org/joc
Synthesis of Conformationally Constrained Diaminodicarboxylic Acid
Derivatives
Robin A. Weatherhead, Michael D. Carducci, and Eugene A. Mash*
Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721-0041
emash@u.arizona.edu
Received September 1, 2009
Functionally protected forms of three conformationally constrained diaminodicarboxylic acids were
synthesized and characterized. 2,20-Diaminospiro[3.3]heptane-2,20-dicarboxylic acid, an analogue of
diaminopimelic acid, was prepared in racemic form and the structure established by X-ray crystal-
lographic analysis of the methyl ester hydrochloride. trans-1,4-Diaminocyclohexane-1,4-dicarbo-
xylic acid was prepared and its structure established by X-ray crystallographic analysis of
the corresponding Cbz-protected ethyl ester. cis- and trans-2,6-diamino-1,2,3,5,6,7-hexahydro-s-
indacene-2,6-dicarboxylic acids were synthesized and the structures assigned by X-ray crystal-
lographic analysis of the corresponding Boc-protected ethyl ester and Cbz-protected ethyl ester,
respectively.
Introduction
Interest in the chemistry of diaminodicarboxylic acids
has grown following the recognition that these are impor-
tant biological agents. Diaminopimelic acids (DAPs)
such as (2S,6S)-1 and (2S,6R)-2 are essential for the
growth of bacteria and plants.1 Dityrosine (3) and isodi-
tyrosine (4) stabilize structural proteins in bacteria
and plants.2 DAP- and isodityrosine-containing peptides
exhibit antibiotic and antitumor activities.3 These com-
pounds inspired syntheses of a number of structurally
related unnatural diaminodicarboxylic acids intended to
enhance bioactivity and/or control peptide secondary
structure.4
Novel diaminodicarboxylic acids have also been used in
assembly of nanoscale structures.5 Our interest in crystal
engineering using 1,4-piperazine-2,5-dione scaffolds6 led to
a need for compounds 5-7 for construction of linear piper-
azinedione oligomers.7 2,20-Diaminospiro[3.3]heptane-2,
(1) Cox, R. J. Nat. Prod. Rep. 1996, 13, 29–43.
(2) (a) Andersen, S. O. Biochim. Biophys. Acta 1964, 93, 213–215. (b) Fry,
S. C. Biochem. J. 1982, 204, 449–455.
(3) (a) Berges, D. A.; DeWolf, W. E. Jr.; Dunn, G. L.; Grappel, S. F.;
Newman, D. J.; Taggart, J. J.; Gilvarg, C. J. Med. Chem. 1986, 29, 89–95. (b)
Jolad, S. D.; Hoffmann, J. J.; Torrance, S. J.; Wiedhopf, R. M.; Cole, J. R.;
Arora, S. K.; Bates, R. B.; Gargiulo, R. L.; Kriek, G. R. J. Am. Chem. Soc.
1977, 99, 8040–8044. (c) Kase, H.; Kaneko, M.; Yamada, K. J. Antibiot.
1987, 40, 450–454. (d) Kase, H.; Kaneko, M.; Yamada, K. J. Antibiot. 1987,
40, 455–458.
(4) (a) Cox, R. J.; Sutherland, A.; Vederas, J. C. Bioorg. Med. Chem. 2000,
8, 843–871. (b) Lygo, B.; Crosby, J.; Peterson, J. A. Tetrahedron 2001, 57,
6447–6453. (c) Williams, R. M.; Fegley, G. J.; Gallegos, R.; Schaefer, F.;
Pruess, D. L. Tetrahedron 1996, 52, 1149–1164.
(5) Schafmeister, C. E.; Brown, Z. Z.; Gupta, S. Acc. Chem. Res. 2008, 41,
1387–1398.
(6) Ntirambepura, D.; Jagadish, B.; Nichol, G. S.; Carducci, M. D.;
Dawson, A.; Rajapakshe, A.; Oliver, A. G.; Clegg, W.; Harrington, R. W.;
Layne, L., Jr.; Margolis, J. I.; Mash, E. A. Cryst. Growth Des. 2008, 8,
3257-3270 and references cited therein.
ꢀ
(7) (a) Ridvan, L.; Budesı
´
nsky, M.; Tichy, M.; Malon, P.; Zavada, J.;
sarova, I. Tetrahedron 1999, 55, 12331–12348. (b) Kloster, R. A.
Ph.D. Dissertation, University of Arizona, 2003.
ꢀ
Podlaha, J.; Cı
´
DOI: 10.1021/jo901892d
r
Published on Web 10/22/2009
J. Org. Chem. 2009, 74, 8773–8778 8773
2009 American Chemical Society

Weatherhead et al.
JOCArticle
20-dicarboxylic acid (5) is a DAP analogue that is capable of
supporting enantiomerism, and to the best of our knowledge
is unknown. 1,4-Diaminocyclohexane-1,4-dicarboxylic acid
(6) is achiral, but can exist as cis and trans diastereomers.
Both diastereomers have previously been prepared.8 How-
ever, the issue of stereochemistry was unresolved at the time
our work began.7b 2,6-Diamino-1,2,3,5,6,7-hexahydro-s-
indacene-2,6-dicarboxylic acid (7) is similar to 6 in that it is
achiral but can exist as cis and trans diastereomers. Precur-
sors to these diastereomers have previously been prepared,9
but stereochemistry remains unassigned to the diastereo-
meric products.10 We report herein syntheses of derivatives
of racemic 5, trans-6, cis-7, and trans-7, along with crystallo-
graphic analyses that establish the structures of these four
compounds.
SCHEME 1. Synthesis of Derivatives 12-15 of 2,20-
Diaminospiro[3.3]heptane-2,20-dicarboxylic Acida
aReagents: (a) PhMgBr, Et2O. (b) (COOH)2, Na2(COO)2, heat.
(c) RuCl3, NaIO4, acetonitrile, CCl4, water. (d) KCN, (NH4)2CO3,
EtOH, water. (e) NaOH, water, heat; Cbz-Cl, acetone. (f) Cs2CO3,
water; CH3I, DMF. (g) H2, Pd/C, EtOAc; HCl (g), Et2O.
SCHEME 2. Synthesis of Derivatives 17-21 of trans-1,4-Dia-
mino-1,4-cyclohexanedicarboxylic Acida
Results
The synthesis of functionally protected forms of 2,20-
diaminospiro[3.3]heptane-2,20-dicarboxylic acid is depicted
in Scheme 1. The dimethyl ester of Fecht acid, (-8,11 was
treated with an excess of phenylmagnesium bromide, produ-
cing diol (-912 in 98% yield. Acid-catalyzed double elimina-
tion produced diene 1012 in 70% yield. Rhodium-catalyzed
oxidative cleavage of the alkene groups gave dione 1113 in
51% yield. Application of the Bucherer-Bergs reaction to 11
produced the bis-hydantoin (-12 quantitatively. Base
hydrolysis, followed by N-acylation with Cbz-Cl gave dicarbo-
xylic acid (-13 in 73% yield over the two steps. Treatment
of (-13 with cesium carbonate, lyophilization, and reac-
tion of the salt with iodomethane in DMF produced
diester (-14. Hydrogenolysis over Pd/C in ethyl acetate,
followed by treatment with gaseous HCl, provided the bis-
amine hydrochloride (-15 in 61% yield from (-13.
aReagents: (a) KCN, NH4Cl, water; Ph(CO)Cl, K2CO3, THF, water. (b)
concd HBr, heat. (c) Cbz-Cl, NaHCO3, water. (d) Cs2CO3, water; CH3I,
DMF. (e) H2, Pd/C, EtOAc.
The synthesis of functionally protected forms of trans-1,4-
diamino-1,4-cyclohexanedicarboxylic acid is depicted in
Scheme 2. Following the procedure of Paventi et al.,14
application of the Strecker reaction to 1,4-cyclohexane-
dione (16), followed by treatment of the crude product
with benzoyl chloride and base, gave a single isomer of
dinitrile 17 in quantitative yield over the two steps.
Hydrolysis under strongly acidic conditions produced
the hydrobromide salt 18 in 86% yield. Reaction of 18
with Cbz-Cl gave dicarboxylic acid 19 in 63% yield.
Treatment with cesium carbonate, lyophilization, and
reaction of the salt with iodomethane in DMF produced
diester 20 in 50% yield. Hydrogenolysis over Pd/C in ethyl
acetate provided the diaminodicarboxylic ester 21 in 93%
yield.
(8) (a) Zelinsky, N.; Schlesinger, N. Berichte 1907, 40, 288–290. (b) Piper,
J. R.; Stringfellow, C. R., Jr.; Johnston, T. P. J. Med. Chem. 1966, 9, 911–920.
(c) Chu, Y.; Lynch, V.; Iverson, B. L. Tetrahedron 2006, 62, 5536–5548.
(9) Kotha, S.; Brahmachary, E. J. Org. Chem. 2000, 65, 1359–1365.
(10) Kumaradhas, P.; Gupta, K. R.; Kotha, S.; Brahmachari, E.;
Nirmala, K. A. Anal. Sci. X-ray Struct. Anal. Online 2008, 24, x65–x66.
(11) Rice, L. M.; Grogan, C. H. J. Org. Chem. 1961, 26, 54–58.
(12) Backer, H. J.; Kemper, H. G. Recl. Trav. Chim. Pays-Bas. 1938,
1248–1258.
ꢀ
(13) Gore, J.; Denis, J.-M.; Leriverend, P.; Conia, J.-M. Bull. Soc. Chim.
Fr. 1968, 6, 2432–2437.
(14) Paventi, M.; Chubb, F. L.; Edward, J. T. Can. J. Chem. 1987, 65,
2114–2117.
8774 J. Org. Chem. Vol. 74, No. 22, 2009

Weatherhead et al.
JOCArticle
SCHEME 3. Synthesis of Derivatives 22-25 of cis- and
trans-2,6-Diamino-1,2,3,5,6,7-hexahydro-s-indacene-
2,6-dicarboxylic Acida
conversion of Fecht acid to diene 10.11,12 While oxidation of
similar systems yielded pinacol rearranged products,16 ruthe-
nium-catalyzed oxidative cleavage of diene 10 generated
dione 11 in good yield.17 Bis-hydantoin (-12 formed under
Bucherer-Bergs conditions in high yield, but hydrolysis and
protection were difficult to scale up, and so generation of the
N-Cbz acid (-13 proved to be a bottleneck. Esterification to
(-14 and hydogenolysis provided (-15.
Synthesis of diaminodicarboxylic ester 21 was previously
described,8 but by somewhat different methods. One synth-
esis prepared compound 20 and confirmed its trans stereo-
chemistry by X-ray crystallographic analysis.8c However, the
structure reported here is polymorphic with the previously
reported structure.
aReagents: (a) (Boc)2O, CH2Cl2, heat. (b) (Cbz)2O, CH2Cl2, heat.
Although the synthesis of diaminodicarboxylic esters 22
and 23 was previously described,9 and a crystal structure of
the isonitrile precursor to 23 was recently published,10 no
definitive structural identification linked to the chromato-
graphic behavior of 22 and 23 or precursors to these com-
pounds has appeared. The crystal structures of 24 and 25
now provide this identification.
These compounds will be used in our future crystal
engineering efforts, and may also be useful to investigators
working to design and produce bioactive peptide ligands.
The synthesis of functionally protected forms of cis- and
trans-2,6-diamino-1,2,3,5,6,7-hexahydro-s-indacene-2,6-di-
carboxylic acids is depicted in Scheme 3. A mixture of
aminoesters 22 and 23 was produced from a mixture of the
corresponding isonitrile-esters according to the procedure of
Kotha and Brahmachary.9 Aminoesters 22 and 23 were
easily separated by chromatography, and were converted
to the corresponding carbamates 24 and 25 by treatment
with Boc anhydride and Cbz anhydride in 94% and 90%
yields, respectively.
Experimental Section18
A summary of crystallographic data for compounds (-15,
20, 24, and 25 is given in Table 1. Structures drawn from
crystal structure data illustrating molecular conformations
appear in Figure 1. Complete crystallographic data (CIF
files) and brief descriptions of the molecular conformations
and the supramolecular assemblies observed in the crystals
appear in the Supporting Information that accompanies this
article.
Dimethyl Spiro[3.3]heptane-2,6-dicarboxylate ((-8).11 Oxa-
lyl chloride (7.0 mL, 80 mmol) was added to a solution of
spiro[3.3]heptane-2,6-dicarboxylic acid11 (5.71 g, 31 mmol) in
dry CH2Cl2 (40 mL) under argon. The solution was stirred at
room temperature for 3 h. The majority of solvent was then
removed in vacuo, the flask was cooled in an ice-water bath,
and dry MeOH (40 mL) was slowly added. The solution was
allowed to warm to room temperature and was stirred over-
night. Volatiles were then removed under vacuum. The residue
was taken up in EtOAc (250 mL) and the solution was washed
with NaHCO3 (2 ꢀ 250 mL) and brine (250 mL), dried (MgSO4),
filtered, and concentrated to give 6.56 g (31 mmol, 100%) of
(-8 as a pale yellow oil, Rf 0.46 (50% EtOAc/hexanes, blue in
anisaldehyde stain). IR (NaCl) (cm-1) 1733; 1H NMR (300
MHz, CDCl3) δ 2.13 (8H, m), 2.87 (2H, pentet, J=8.5 Hz), 3.53
(6H, s); 13C NMR (75 MHz, CDCl3) δ 32.4, 36.5, 37.1, 37.7,
51.4, 175.4; HRMS (FABþ) calcd for C11H17O4 (M þ H)þ
213.1127, found 213.1134 (þ3.2 ppm).
TABLE 1. Crystallographic Data for Compounds (-15, 20, 24, and 25
compd
(-15
20
24
25
formula
C11H20Cl2N2O4 C26H30N2O8 C31H47N3O9 C34H36N2O8
wt (g mol-1
temp (K)
radiation
cryst syst
)
315.19
293(2)
Mo KR
monoclinic
P21/c
8.681(6)
16.982(12)
11.343(8)
90
498.52
100(2)
Mo KR
605.72
170(2)
Mo KR
600.65
170(2)
Mo KR
monoclinic monoclinic triclinic
space group
a (A)
b (A)
P21/c
10.2758(6)
7.1597(4)
P21/c
P1
10.7517(11) 7.7824(8)
36.694(4)
9.1091(9)
11.1134(11)
98.037(2)
106.442(2)
100.826(2)
726.43(13)
1
c (A)
16.6143(10) 9.4807(10)
90 90
92.7750(10) 115.835(2)
90 90
1220.91(12) 3366.5(6)
R (deg)
β (deg)
γ (deg)
V (A3)
Z
2,6-Di(diphenylhydroxy)methylspiro[3.3]heptane ((-9).12
A
90.511(13)
90
1672(2)
4
solution of PhMgBr in Et2O (2.9 M, 100 mL, 0.29 mol) was
injected into a solution of (-8 (12.4 g, 58 mmol) in Et2O (100
mL) under argon and the mixture was cooled in an ice-water
bath. The reaction was warmed to room temperature and heated
at reflux for 1.5 h. The solution was then cooled in an ice-water
bath and a saturated aqueous solution of ammonium chloride
was slowly added until the reaction was quenched (exothermic
reaction ceased). The solution was stirred for an additional
10 min at room temperature, then diluted with brine (1 L) and
extracted with EtOAc (5 ꢀ 200 mL). The organic extracts were
washed with brine (500 mL), dried (MgSO4), filtered, and
concentrated to leave a yellow oil. This material was subjected
to flash chromatography (230-400 mesh silica) using 100%
2
4
R1 (obsd data) 0.0643
wR2 (all data) 0.1310
0.0393
0.1043
0.997
0.0678
0.2258
0.895
0.0418
0.0864
0.867
GOF on F2
0.774
Discussion
Synthesis of diaminodicarboxylic ester (-15 was more
difficult than anticipated. We planned to construct the spiro-
[3.3]heptane ring system from pentaerythritol tetrabromide
using protocols established for monocyclic small-ring sys-
tems.15 This approach failed, and so a longer route was
employed (Scheme 1). Others had previously described the
(16) (a) Graham, S. H.; Williams, A. J. S. J. Chem. Soc. 1959, 4066–4073.
(b) Conley, R. T. Recl. Trav. Chim. Pays-Bas. 1962, 81, 198–201.
(17) (a) Carlsen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B.
J. Org. Chem. 1981, 46, 3936–3938. (b) Yang, D.; Zhang, C. J. Org. Chem.
2001, 66, 4814–4818.
(15) (a) O’Donnell, M. J.; Bruder, W. A.; Eckrich, T. M.; Shullenberger,
D. F.; Staten, G. S. Synthesis 1984, 127–128. (b) Kalvin, D.; Ramalingam,
K.; Woodard, R. Synth. Commun. 1985, 15, 267–272.
(18) The General Experimental Section appears in the Supporting In-
formation.
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FIGURE 1. Conformers of compounds (-15, 20, 24, and 25 observed by X-ray crystallography.
hexanes as elutant until all UV active byproduct was removed.
The elutant was then changed to 20% EtOAc/hexanes, giving
26.4 g (57 mmol, 98%) of (-9 as a light yellow foam, Rf 0.13
(10% EtOAc/hexanes, brown in anisaldehyde stain), mp 52-
55 °C (lit.12 mp 56 °C), which was used without further purifica-
tion. IR (KBr) (cm-1) 3506 (br), 1449, 751, 702; 1H NMR (300
MHz, DMSO-d6) δ 1.54 (2H, dt, J=3.9, 7.2 Hz), 1.82 (2H, dt, J=
3.9, 7.3 Hz), 1.95 (2H, t, J=10.1 Hz), 2.07 (2H, t, J=9.9 Hz), 3.18
(2H, pentet, J=8.5 Hz), 5.33 (2H, s), 7.12 (4H, m), 7.21 (4H, t,
J=7.4 Hz), 7.24 (4H, t, J=7.4 Hz), 7.32 (4H, d, J=7.8 Hz), 7.34
(4H, d, J=7.6 Hz); 13C NMR (75 MHz, DMSO-d6) δ 32.6, 34.3,
35.9, 38.3, 76.7, 126.0, 126.1, 126.2, 127.6, 147.4; HRMS
(FABþ) calcd for C33H31O (M - OH)þ 443.2375, found
443.2363 (-2.6 ppm).
The oil was dried to a sticky solid by azeotroping with MeOH,
and the material was further purified by trituration with hot
MeOH to give eventually a yellow solid. The MeOH slurry was
cooled in a freezer (-22 °C) overnight and filtered, then the solid
was washed sparingly with cold MeOH to give 14.9 g (35 mmol,
70%) of 10 as a light yellow solid, Rf 0.54 (20% Et2O/hexanes,
black in PMA stain), mp 112-113 °C (lit.12 mp 116-116.5 °C).
1
IR (KBr) (cm-1) 3086, 3018, 1499, 1443, 702; H NMR (300
MHz, CDCl3) δ 3.02 (8H, s), 7.22 (20H, m); 13C NMR (75 MHz,
CDCl3) δ 35.3, 44.9, 126.3, 128.0, 128.8, 134.0, 135.2, 140.6.
Spiro[3.3]heptane-2,6-dione (11).13 To a solution of 10 (7.97 g,
19.0 mmol) in a mixture of acetonitrile (120 mL), CCl4
(120 mL), and water (180 mL) were added RuCl3 dihydrate
(0.65 g, 3.1 mmol, 16 mol %) and NaIO4 (40 g, 0.19 mol) in one
portion. The solution was stirred at room temperature for 5 min,
and then heated at reflux for 1.5 h. The solution was then cooled
to room temperature and the insoluble salts were collected by
filtration and extracted with CH2Cl2 in a Soxhlet extractor
overnight. The CH2Cl2 phases were combined and concentrated
to leave a brown residue. The material was dry loaded onto
silica, and subjected to gravity chromatography (230-400 mesh
silica) with 35% EtOAc/hexanes as elutant to give the product as
a yellow oil (contaminated with I2). The oil was purified by
trituration with hot hexanes to give a light yellow solid. The
slurry was cooled in the freezer (-22 °C) overnight, then the
solid was collected by filtration, washed with hexanes, and
dried to give 1.2 g (9.7 mmol, 51%) of 11 as a light yellow solid,
Rf 0.5 (40% EtOAc/hexanes, black in anisaldehyde stain),
2,6-Di(benzhydrylidene)spiro[3.3]heptane (10).12 A ground
mixture of oxalic acid (88.1 g, 0.71 mol) and sodium oxalate
(15.5 g, 0.12 mol) was deposited in a beaker containing oily solid
(-9 (22.9 g, 50 mmol), and the contents were intermixed. A
watch glass was placed over the beaker and the neat mixture
thermolyzed in an oil bath heated to 175-180 °C for 2 h. The
material was then cooled to room temperature and partitioned
between water (500 mL) and Et2O (1 L). The heterogeneous
solvent system was vacuum filtered, the filtrate was washed
thoroughly with Et2O, the organic phase was separated, and the
aqueous phase was extracted with Et2O (3 ꢀ 250 mL). The Et2O
fractions were combined, washed with NaHCO3 (2 ꢀ 250 mL)
and brine (250 mL), treated with charcoal, dried (MgSO4),
filtered, and concentrated under vacuum to leave a yellow oil.
8776 J. Org. Chem. Vol. 74, No. 22, 2009

Weatherhead et al.
JOCArticle
mp 59-62 °C (lit13 mp 81 °C), which was used without further
purification. IR (KBr) (cm-1) 1781; 1H NMR (300 MHz,
CDCl3) δ 3.34 (8H, s); 13C NMR (75 MHz, CDCl3) δ 23.4,
58.6, 204.7. Anal. Calcd for C7H8O2: C 67.73, H 6.50. Found: C
66.90, H 6.59.
(230-400 mesh silica, pretreated 1% NEt3) with 50% EtOAc/
hexanes as elutant to give 173 mg of the crude diester (-14 as a
sticky, clear oil, Rf 0.34 (50% EtOAc/hexanes, blue-yellow in
PMA stain). This material was taken up in EtOAc (10 mL) and
treated with 10% Pd/C (40 mg) under H2 (55 psi) in a hydro-
genator. After 20 h, the contents were filtered, solids were
washed with CH2Cl2, and the filtrate was concentrated. The
resulting oil was dissolved in Et2O (25 mL), the solution was
cooled in an ice-water bath, and anhydrous HCl gas was
bubbled through the solution until a white precipitate was
observed. The Et2O solvent was decanted and the sticky solid
was dried under vacuum to give a dry tan solid. The solid was
triturated with hot acetonitrile, then the solution was cooled to
room temperature and filtered to give 74.1 mg (0.24 mmol, 61%
for two steps) of (-15 HCl salt as an off-white solid, Rf 0.13
(50% EtOH/EtOAc, yellow in ninhydrin stain), mp 226-
228 °C. IR (KBr) (cm-1) 3421(br), 1741; 1H NMR (300 MHz,
CD3OD) δ 2.63 (2H, d, J=15.1 Hz), 2.71 (2H, d, J=13.7 Hz),
2.78 (1H, d, J=4.4 Hz), 2.82 (1H, d, J=4.4 Hz), 2.93 (1H, d, J=
3.4 Hz), 2.97 (1H, d, J=3.4 Hz), 3.87 (6H, s); 13C NMR (75
MHz, CD3OD) δ 31.2, 43.3, 44.1, 54.0, 54.1, 172.3; HRMS
(FABþ) calcd for C11H19N2O4 (M þ H)þ 243.1345, found
243.1343 (-0.8 ppm).
Bis(spiro-2,6-hydantoin)spiro[3.3]heptane ((-12). Potassium
cyanide (1.65 g, 25 mmol) and ammonium carbonate (13.3 g,
85 mmol) were added to a solution of 11 (1.05 g, 8.5 mmol) in
absolute EtOH (30 mL) and water (30 mL). The solution was
heated in an oil bath at 60 °C. The solution cleared after 3 h of
heating, and then a white precipitate gradually formed. After
3 d, the reaction was cooled to room temperature, and further
cooled in an ice-water bath, then concd HCl (ca. 20 mL) added
dropwise to the solution over a 1 h period until a pH of 2 was
reached. The reaction mixture was cooled in a freezer (-22 °C)
overnight, Et2O (60 mL) was added, the cold mixture was
vacuum filtered, and the precipitate was washed with Et2O.
The white solid was further purified by vigorous stirring with
absolute EtOH (100 mL) at room temperature overnight. The
mixture was filtered to give 2.28 g (8.6 mmol, 100%) of (-12 as a
white solid, mp 358 °C dec. IR (KBr) (cm-1) 3188 (br), 1781,
1
1725; H NMR (300 MHz, DMSO-d6) δ 2.21 (2H, d, J=12.5
Hz), 2.28 (2H, d, J=12.7 Hz), 2.39 (2H, dd, J=3.4, 12.6 Hz),
2.54 (2H, dd, J=3.2, 12.5 Hz), 8.15 (2H, s), 10.45 (2H, s); 13
C
trans-1,4-Di(phenylcarbonyl)aminocyclohexane-1,4-dinitrile
(17).8 Potassium cyanide (5.3 g, 81 mmol) was added with
stirring to a solution of 1,4-cyclohexanedione (4.35 g, 39 mmol)
and ammonium chloride (4.3 g, 81 mmol) in water (25 mL)
cooled in an ice-water bath. A thick white precipitate formed
after a few minutes. The ice bath was removed and the reaction
mixture was stirred at room temperature for 2 d. The mixture
was filtered, then the white precipitate was washed with a
minimum of cold water and cold CHCl3 and dried in vacuo to
leave a white solid (6.4 g). This material was immediately
deposited into a mixture of K2CO3 (15.6 g, 110 mmol) in THF
(780 mL) and water (1 L). Benzoyl chloride (9.5 mL, 82 mmol)
was added to the mixture, and the reaction was vigorously
stirred at room temperature. After a few minutes, a white
precipitate formed. After 3 d, the mixture was filtered, then
the precipitate was washed with water and dried in vacuo to give
13.6 g (37 mmol, 100%) of 17 as a white solid, mp 316-318 °C,
Rf 0.78 (5% MeOH/EtOAc, light purple in anisaldehyde). IR
(KBr) (cm-1) 1659; 1H NMR (300 MHz, DMSO-d6) δ 1.74
(pentet, minor salt impurity), 2.06 (4H, d, J=10.3 Hz), 2.61 (4H,
d, J=10.0 Hz), 3.58 (pentet, minor salt impurity), 7.49 (4H, t, J=
NMR (75 MHz, DMSO-d6) δ 27.4, 44.0, 44.2, 57.1, 156.1, 178.5;
HRMS (EI) calcd for C11H12N4O4 (Mþ) 264.0853, found
264.0865 (þ4.5 ppm).
2,6-Di(benzyloxycarbonyl)aminospiro[3.3]heptane-2,6-dicar-
boxylic Acid ((-13). (Note: Successful reaction is limited to this
scale.) Compound (-12 (136 mg, 0.52 mmol) was mixed with
3 M NaOH solution (1 mL) and heated at vigorous reflux for
24 h. A trace amount of precipitate developed after this time.
The solution was cooled in an ice-water bath, and a solution of
benzyl chloroformate (1 mL, 7.0 mmol) in acetone (5 mL)
followed by NaOH (400 mg, 10 mmol) in water (5 mL) were
added. The reaction was warmed to room temperature and
stirred overnight. The reaction mixture was washed with Et2O
(10 mL), the Et2O phase was back-extracted with water (10 mL),
and the aqueous fractions were combined, diluted with water
(100 mL), and acidified with concd HCl until a white precipitate
was observed (pH 2). The acidified solution was extracted
with EtOAc (3 ꢀ 100 mL). Extraction forms an emulsion that
was collected together with the EtOAc layer. The emulsified
organic phase was dried (MgSO4), filtered, and concentrated to
give an opaque oil, which was freeze-pump-thawed (twice)
and triturated with hot hexanes to produce 178 mg (0.37 mmol,
73% for two steps) of (-13 as a white solid, mp 192-194 °C. IR
(KBr) (cm-1) 3292, 1709, 1644; 1H NMR (300 MHz, CD3OD) δ
2.37 (4H, t, J=11.7 Hz), 2.74 (4H, d, J=9.5 Hz), 5.05 (4H, s),
7.32 (10H, m); 13C NMR (75 MHz, CD3OD) δ 33.0, 45.0, 45.5,
55.4, 67.3, 128.6, 128.9, 129.4, 138.1, 157.8, 177.2; HRMS
(FABþ) cacld for C25H27N2O8 (M þ H)þ 483.1767, found
483.1744 (-4.9 ppm).
7.6 Hz), 7.57 (2H, d, J=7.3 Hz), 7.90 (4H, d, J=7.3 Hz); 13
C
NMR (75 MHz, DMSO-d6) δ 30.7, 50.4, 119.4, 127.8, 128.3,
131.9, 133.26, 166.8; HRMS (EIþ) calcd for C22H20N4O2 (Mþ)
372.1586, found 372.1573 (-3.4 ppm).
trans-1,4-Diaminocyclohexane-1,4-dicarboxylic Acid Dihydro-
bromide (18).8c A solution of 17 (15.8 g, 42.0 mmol) in concd
HBr (160 mL) was heated at reflux for 4 d. (Benzoic acid was
observed as a white crystalline material in and around the lip of
the flask after 24 h.) The solution was cooled to room tempera-
ture and volatiles were removed in vacuo aided by azeotroping
with t-BuOH, to leave a brown solid, which was purified by
trituration with absolute EtOH. The suspension was filtered and
the solid was washed thoroughly with EtOH to leave a white
solid. Due to the presence of a salt impurity (observable by 1H
NMR as signals present in the 6-8 ppm range), the white solid
was vigorously stirred in absolute EtOH (150 mL) overnight.
The slurry was then filtered to give 13.3 g (36 mmol, 86%) of 18
as a white solid, mp 303 °C dec. IR (KBr) (cm-1) 3018 (br), 1715;
1H NMR (200 MHz, CD3OD) δ 2.21 (2H, d, J=9.4 Hz), 2.26
(2H, d, J=9.6 Hz), 2.29 (2H, d, J=9.8 Hz), 2.34 (2H, d, J=9.5
Hz), 4.95 (6H, s); 13C NMR (50 MHz, CD3OD) δ 29.2, 58.0,
172.2; HRMS (FABþ) calcd for C8H15N2O4 (MþH)þ 203.1032,
found 203.1031 (-0.5 ppm).
Dimethyl
2,6-Diaminospiro[3.3]heptane-2,6-dicarboxylate
Hydrochloride ((-15). Dicarboxylic acid (-13 (190 mg, 0.39
mmol) was dissolved in a 5% Cs2CO3 solution (15 mL) by
heating. Lyophilization gave a white salt. Dry DMF (10 mL)
and iodomethane (0.5 mL, 8.0 mmol) were injected into the flask
containing the salt under argon and the reaction was stirred at
room temperature overnight. After 24 h, additional iodo-
methane (0.5 mL, 8.0 mmol) was added, and the reaction was
stirred an additional 24 h. Volatiles were removed under
vacuum, the yellow residue was partitioned between water
(100 mL) and EtOAc (100 mL), and the aqueous phase was
separated and extracted with EtOAc (3 ꢀ 100 mL). The EtOAc
phases were combined, washed with Na2SO3 (100 mL) and
brine (100 mL), dried (MgSO4), filtered, and concentrated to a
yellow sticky solid that was purified by flash chromatography
J. Org. Chem. Vol. 74, No. 22, 2009 8777

Weatherhead et al.
JOCArticle
trans-1,4-Di(benzyloxycarbonyl)aminocyclohexane-1,4-dicar-
boxylic Acid (19).8c A slurry of 18 (1.04 g, 2.9 mmol) in sat. aq
NaHCO3 (250 mL) was heated to boiling until the solution
became clear. The solution was cooled to room temperature, then
further in an ice-water bath. Benzyl chloroformate (3.0 mL, 27
mmol) was slowly added by pipet, and the solution was warmed to
room temperature. After 48 h, the reaction mixture was diluted
with water (250 mL) and extracted with Et2O (250 mL). The
organic phase was discarded. The aqueous phase was acidified
with concd HCl to pH 2, and the solution was extracted with
EtOAc (3 ꢀ 250 mL). MeOH (200 mL) was added to the opaque
EtOAc phase until it became clear. The organic solution was then
dried (Na2SO3) and concentrated under vacuum to leave 850 mg
(1.8 mmol, 63%) of 19 as an off-white solid, mp 254 °C dec. IR
(KBr) (cm-1) 3320, 1733, 1665; 1H NMR (200 MHz, DMSO-d6) δ
1.89 (8H, m), 5.20 (4H, s), 7.36 (10, s), 7.59 (2H, s), 12.38 (2H, br
s); 13C NMR (50 MHz, DMSO-d6) δ 26.4, 57.4, 65.1, 127.6, 127.7,
128.3, 137.0, 155.4, 175.9; HRMS (FABþ) calcd for C24H27N2O8
(M þ H)þ 471.1767, found 471.1770 (þ0.6 ppm).
with a 30% EtOH/EtOAc as elutant to give 1.2 g (3.6 mmol) of
cis-2,6-diamino-1,2,3,5,6,7-hexahydro-s-indacene-2,6-dicarbo-
xylic acid diethyl ester (22) as an off-white solid, Rf 0.20 (30%
EtOH/EtOAc, pink in ninhydrin stain), mp 134 °C (lit.9 mp
123-125 °C), and 1.4 g (4.2 mmol) of trans-2,6-diamino-
1,2,3,5,6,7-hexahydro-s-indacene-2,6-dicarboxylic acid diethyl
ester (23) as an off-white solid, Rf 0.40 (30% EtOH/EtOAc, pink
in ninhydrin stain), mp 90-91 °C (lit.9 mp 91-93 °C). Spectral
data for 22: IR (KBr) (cm-1) 3405, 3381, 1725; 1H NMR (300
MHz, CDCl3) δ 1.27 (6H, t, J=7.1 Hz), 1.79 (4H, s), 2.80 (4H, d,
J=15.4 Hz), 3.51 (4H, d, J=15.1 Hz), 4.20 (4H, q, J=7.1 Hz),
7.04 (2H, s); 13C NMR (75 MHz, CDCl3) δ 14.1, 45.8, 61.2, 65.3,
121.2, 139.1, 176.2; HRMS (FABþ) calcd for C18H25N2O4 (M
þ H)þ 333.1814, found 333.1822 (þ2.2 ppm). Spectral data for
23: IR (KBr) (cm-1) 3373, 3300, 3260, 1741; 1H NMR (300
MHz, CDCl3) δ 1.25 (6H, t, J=7.2 Hz), 1.78 (4H, s), 2.78 (4H, d,
J=15.4 Hz), 3.45 (4H, d, J=15.4 Hz), 4.18 (4H, q, J=7.2 Hz),
7.02 (2H, s); 13C NMR (75 MHz, CDCl3) δ 14.0, 45.5, 61.0, 65.0,
121.1, 139.0, 176.3; HRMS (FABþ) calcd for C18H25N2O4 (M
þ H)þ 333.1814, found 333.1824 (þ2.9 ppm).
Dimethyl trans-1,4-Di(benzyloxycarbonyl)aminocyclohexane-
1,4-dicarboxylate (20).8c A slurry of 19 (10.4 g, 22 mmol) in 5%
aqueous Cs2CO3 (75 mL) was heated until solution was effected.
The aqueous solution was then lyopholized to give a white solid.
Iodomethane (27.4 mL, 0.44 mol) was injected into a slurry of the
salt in DMF (100 mL) under argon, and the reaction mixture was
stirred at room temperature for 48 h. Volatiles were removed under
vacuum to leave a yellow residue, which was taken up in water
(200 mL) and extracted with EtOAc (3 ꢀ 200 mL). The organic
extracts were dried (MgSO4), filtered, and concentrated to give a
yellow solid. The solid was triturated with hot Et2O, then the
suspension was cooled to room temperature and filtered to give a
light yellow solid. This material was further purified by trituration
with a minimum of cold EtOAc to provide 5.53 g (11.1 mmol,
50%) of 20 as a white solid, mp 266 °C, Rf 0.4 (40% EtOAc/
hexanes, black in PMA stain). IR (KBr) (cm-1) 3307, 1732, 1689;
1H NMR (200 MHz, CDCl3) δ 2.10 (4H, d, J=12.7 Hz), 2.09 (4H,
d, J=12.5 Hz), 3.67 (6H, s), 5.02 (2H, s), 5.09 (4H, s), 7.35 (10H, s);
13C NMR (50 MHz, CDCl3) δ 27.2, 52.6, 58.1, 66.9, 128.1, 128.2,
128.5, 136.0, 155.5, 174.2; HRMS (FABþ) calcd for C26H31N2O8
(M þ H)þ 499.2080, found 499.2086 (þ1.2 ppm).
Diethyl cis-2,6-Di(tert-butoxycarbonyl)amino-1,2,3,5,6,7-
hexahydro-s-indacene-2,6-dicarboxylate (24). Di-tert-butyldicar-
bonate (206 mg, 0.92 mmol) was added in one portion to a
solution of 22 (102 mg, 0.36 mmol) in CH2Cl2 (5 mL) and the
solution was heated to reflux overnight. The reaction mixture was
diluted with CH2Cl2 (100 mL) and washed with brine (100 mL),
thenthe organicphasewasseparated, dried(MgSO4), filtered, and
concentrated to give a light yellow solid, which was purified by
trituration with hot hexanes. The suspension was cooled to room
temperature and filtered to give 154 mg (0.29 mmol, 94%) of 24 as
an off-white solid, Rf 0.33 (30% EtOAc/hexanes, light pink in
ninhydrin stain), mp 187-188 °C. IR (KBr) (cm-1) 3326, 1727,
1690; 1H NMR (300 MHz, CDCl3) δ 1.22 (6H, t, J=7.1 Hz), 1.38
(18H, s), 3.09 (4H, d, J=16.1 Hz), 3.53 (4H, d, J=16.1 Hz), 4.18
(4H, q, J=7.1 Hz), 5.10 (2H, br s), 6.98 (2H, s); 13C NMR (75
MHz, CDCl3) δ 14.1, 28.2, 43.4, 61.4, 66.2, 79.8, 120.6, 138.7,
154.9, 173.3; HRMS (FABþ) cacld for C28H41N2O8 (M þ H)þ
533.2863, found 533.2860 (-0.5 ppm).
Diethyl trans-2,6-Di(benzyloxycarbonyl)amino-1,2,3,5,6,7-
hexahydro-s-indacene-2,6-dicarboxylate (25). Dibenzyl dicarbo-
nate (190 mg, 0.66 mmol) was added in one portion to a solution of
23 (55 mg, 0.17 mmol) in CH2Cl2 (5 mL), and the solution was
heated to reflux for 1 h. A white precipitate was observed. Volatiles
were removed under vacuum to leave a white solid, which was
purified by trituration with hot hexanes. The suspension was
cooled to room temperature and filtered to give 79 mg (0.15 mmol,
90%) of 25 as a white solid, Rf 0.91 (100% EtOAc, light pink in
ninhydrin stain), mp 250 °C dec; IR (KBr) (cm-1) 3340, 1733,
1725; 1H NMR (300 MHz, CDCl3) δ 1.11 (6H, t, J=7.0 Hz), 3.15
(4H, d, J=16.4 Hz), 3.38 (4H, d, J=16.1 Hz), 4.07 (4H, q, J=6.9
Hz), 5.01 (4H, s), 6.99 (2H, s), 7.33 (10H, s), 8.03(2H, s);13CNMR
(75 MHz, CDCl3) δ 13.9, 42.4, 60.7, 65.2, 65.8, 120.4, 127.7, 127.8,
128.3, 136.9, 138.5, 155.6, 173.1. Anal. Calcd for C34H36N2O8: C
67.99, H 6.04, N 4.66. Found: C 67.50, H 6.18, N 4.87.
Dimethyl trans-1,4-Diaminocyclohexane-1,4-dicarboxylate
(21).8b,c Ester 20 (1.77 g, 3.6 mmol) and 10% Pd/C (0.42 g) in a
mixture of MeOH (50 mL) and EtOAc (80 mL) were shaken under
H2 (55 psi) in a hydrogentator for 20 h. The reaction mixture was
treated with charcoal and filtered, then the solids were washed with
CH2Cl2. The solution was concentrated under vacuum to 20 mL
and filtered through a cotton plug. Volatiles were removed under
vacuum to give 770 mg (3.3 mmol, 93%) of 21 as an off-white solid,
mp 116-118 °C (lit.8b mp 122 °C). IR (KBr) (cm-1) 3420, 3359,
3299, 1732; 1H NMR (300 MHz, CDCl3) δ 1.49 (4H, dd, J=4.0,
13.5 Hz), 2.15 (4H, dd, J=3.9, 13.4 Hz), 3.72 (6H, s), 4.85 (4H, br
s); 13C NMR (75 MHz, CDCl3) δ 32.1, 52.7, 57.6, 177.9; HRMS
(FABþ) calcd for C10H19N2O4 (M þ H)þ 231.1345, found
231.1344 (-0.4 ppm).
Diethyl
cis-2,6-Diamino-1,2,3,5,6,7-hexahydro-s-indacene-
Acknowledgment. This work was supported in part by the
Office of Naval Research through the Center for Advanced
Multifunctional Nonlinear Optical Polymers and Molecular
Assemblies, by the National Science Foundation (CHE-
9610374), by Research Corporation, and by the University
of Arizona through the Materials Characterization Program
and the Office of the Vice President for Research.
2,6-dicarboxylate (22) and Diethyl trans-2,6-Diamino-1,2,3,5,6,
7-hexahydro-s-indacene-2,6-dicarboxylate (23).9 Concentrated
HCl (15 mL) was added to a heterogeneous mixture of diethyl
2,6-diisocyano-1,2,3,5,6,7-hexahydro-s-indacene-2,6-dicarbox-
ylate9 (cis and trans, 5.0 g, 10 mmol) in absolute EtOH (150 mL),
and the slurry was stirred at room temperature. Gas was
evolved, and the solution gradually became homogeneous.
After 24 h, the solvent was removed under vacuum to leave a
white solid. This solid was taken up in water (200 mL), then the
solution was basified with concd NH4OH and extracted with
EtOAc (3 ꢀ 200 mL). The organic phase was dried (MgSO4),
filtered, and concentrated under vacuum. The resulting solid
was purified by gravity chromatography (230-400 mesh silica)
Supporting Information Available: General experimental
procedures, proton and carbon NMR spectra for compounds
8-13, 15, and 17-25, and X-ray crystallographic information
files (CIFs) for crystals of 15, 20, 24, and 25. This material is
available free of charge via the Internet at http://pubs.acs.org.
8778 J. Org. Chem. Vol. 74, No. 22, 2009