Lithium Bromide-Promoted Three-Component Synthesis of Oxa-Bridged Tetracyclic Tetrahydroisoquinolines

Article abstract of DOI:10.3987/COM-07-S(U)54

Heating a toluene solution of an α-isocyanoacetamide (1), an aldehyde (2) and an aniline (3) in the presence of lithium bromide at 60 °C provides the oxa-bridged tetracyclic tetrahydroquinoline (4) in good to excellent yield as a mixture of two separable diastereoisomers. In this one-pot multicomponent reaction, one C-N, one C-O and three C-C bonds are formed with concomitant creation of five asymmetric centers and three heterocycles. Fragmentation of epoxy-tetrahydroquinoline (4) under mild acidic conditions affords 4,6-phenanthroline (5).

Full text of DOI:10.3987/COM-07-S(U)54

HETEROCYCLES, Vol. 73, 2007
729
HETEROCYCLES, Vol. 73, 2007, pp. 729 - 742. © The Japan Institute of Heterocyclic Chemistry
Received, 27th July, 2007, Accepted, 13th September, 2007, Published online, 14th September, 2007. COM-07-S(U)54
LITHIUM BROMIDE-PROMOTED THREE-COMPONENT SYNTHESIS
OF OXA-BRIDGED TETRACYCLIC TETRAHYDROISOQUINOLINES
Aude Fayol, Eduardo González-Zamora, Michèle Bois-Choussy, and Jieping
Zhu*
Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette,
France
Abstract – Heating a toluene solution of an α-isocyanoacetamide (1), an
aldehyde (2) and an aniline (3) in the presence of lithium bromide at 60 ˚C
provides the oxa-bridged tetracyclic tetrahydroquinoline (4) in good to excellent
yield as a mixture of two separable diastereoisomers. In this one-pot
multicomponent reaction, one C-N, one C-O and three C-C bonds are formed
with concomitant creation of five asymmetric centers and three heterocycles.
Fragmentation of epoxy-tetrahydroquinoline (4) under mild acidic conditions
affords 4,6-phenanthroline (5).
Dedicated to the memory of Professor Ivar Ugi
INTRODUCTION
By virtue of its inherent convergence, high productivity, its exploratory and complexity-generating power,
multicomponent reaction (MCR) is being recognized as one of the most promising approaches in
diversity oriented syntheses and is undoubtedly well suited for the drug discovery program.1 Among
named MCRs, the Ugi four-component reaction (Ugi-4CR) is without doubt one of the most powerful
transformations.2 Discovered in the late 1950’s by Ugi,3 this MCR has been extensively investigated for
the past twenty years and has became a reference reaction for those working in the field of
multicomponent reactions. Indeed, it belongs to a very rare family of truly four-component reaction in the
sense that each input (carboxylic acid, aldehyde, amine and isocyanide) bearing an organic residue that
can be varied systematically.4 Inspired by Ugi’s pioneering work, many variants have since been
developed taking advantage of the unique carbene-like reactivity of isocyanide.5

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We have been working on the chemistry of α-isocyano acetamide6 as well as α-isocyano acetic acid7 and
have developed an efficient three-component synthesis of 5-aminooxazole by its reaction with an amine
and an aldehyde. Taking advantage of the chemical reactivity of 5-aminooxazole and by fine tuning the
structure of the starting materials, several new multicomponent reactions have subsequently been devised
for the syntheses of a number of polyheterocycles8 and macrocycles.9 One of such reactions involving an
α-isocyanoacetamide (1), an aldehyde (2) and an o-amino cinnamate (3) afforded the
epoxy-tetrahydroquinoline (4) in excellent yield and good level of diastereoselectivity.10 We report herein
full details the development of this three-component reaction and the subsequent acid-promoted
fragmentation of 4 to 4,6-phenanthroline (5) (Scheme 1).
NR1R2
H
R6O2C
H
R
CO2R6
O
O
N
LiBr, toluene
60°C
R3CHO
CN
+
+
R4
NR1R2
R4
NHR5
R3
R
N
R5
4
1
2
3
NR1R2
R6O2C
R
TFA, MeCN
N
R4
0 °C (R5 = H)
N
R3
5
Scheme 1. Three-component synthesis of oxa-bridged polycycle and its fragmentation to
diazaphenanthrene.
RESULTS AND DISCUSSION
Using N-morpholinyl α-isocyano−α-benzyl acetamide (1a),11 an heptanal (2a) and an ortho-amino methyl
cinnamate (3a) as inputs (Scheme 2), we performed a survey of reaction conditions varying the solvents
(MeOH, CF3CH2OH, benzene, toluene), the temperatures (room temperature to 110°C), and the
promoters (LiBr, BF3.OEt2, Yb(OTf)3, Sc(OTf)3, MgSO4).12 Some representative results are summarized
in Table 1. The optimized conditions we found for this three-component reaction consisted of heating a
toluene solution of 2a, 3a and 1a in the presence of LiBr (60 °C). Under these conditions, the tetracyclic
tetrahydroquinoline 4a (Scheme 2) was isolated in 94% yield as a mixture of two separable diastereomers.
The presence of lithium bromide was of utmost importance for the success of this reaction. Indeed, in its
absence, the adduct 4 was isolated in only 6% yield under otherwise identical conditions. LiBr may act as
an activator for both the nucloephilic addition of isocyanide carbon to imine and the subsequent
Diels-Alder reaction.

HETEROCYCLES, Vol. 73, 2007
731
Table 1. Three-component synthesis of 4a, a survey of reaction conditions.a
Entry Solvant Time (h) T (°C) Additive
4a (%)
-
1
2
3
4
5
6
7
MeOH
toluene 24
MeOH 24
toluene 24
MeOH 20
toluene 24
benzene
24
25
25
reflux
reflux
reflux LiBr
60 LiBr
reflux LiBr
-
-
-
-
-
42b
6c
30d
94d
28d
-
8
8
9
10
toluene 15
toluene 15
toluene 15
60
60
60
BF3.Et2O
Yb(OTf)3 20
Sc(OTf)3 16
aGeneral conditions: mole ratio: 1a/2a/3a = 1/1.2/1.0, C = 0.15M ;
bdiastereomeric ratio 5/1; cdiastereomeric ratio 2/1; ddiastereomeric ratio 3/1.
The sequence of events leading to the formation of 4 is outlined in Scheme 2. Reaction of an aniline, an
aldehyde and an α-isocyano acetamide should give the aminooxazole via an iminium 6, then a nitrilium
ion 7 intermediate. Cycloaddition of oxazole 8 as an aza-diene with a properly predisposed dienophile
produced then a bridged tetrahydroquinoline-containing polycycle 4.13,14 It is interesting to note that
Ugi-type condensation is preferably performed in polar protic solvents such as methanol and
trifluoroethanol, whereas in non-polar aprotic solvent, the Passerini-type reaction became competitive.15 It
is thus remarkable that the present multicomponent reaction worked so efficiently in toluene. Lithium
bromide may activate the imine intermediate and thus facilitating the subsequent nucleophilic attack of
the divalent carbon of isocyanide. In the presence of strong Lewis acids such as BF3.OEt2, degradation of
the acid-sensitive 5-aminooxazole may occur decreasing consequently the overall reaction efficiency. It is
worth noting that one C-N, one C-O and three C-C bonds were formed with the concomitant creation of
five asymmetric centers in this one-pot process. The efficiency of this reaction was thus truly remarkable
if one looks at the yield per bond formation.
CO2Me
CO2Me
C6H13
1a
NH
2a + 3a
+
N
H
C6H13
O
+
N
N
6
7
Bn
O
O
CO2Me
N
NH
H
MeO2C
H
Bn
C6H13
O
O
N
N
N
Bn
O
N
H
C6H13
8
4a
Scheme 2. Reaction sequence of the three-component reaction.

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HETEROCYCLES, Vol. 73, 2007
Since five chiral centers were created in this 3CR, 16 pairs of diastereomers would theoretically be
expected. However, only two of them were isolated in a ratio of 3 to 1. The stereochemistry of compound
4a and 4a' was deduced from both mechanistic consideration and NMR studies. The observed coupling
constant between Ha and Hb (JHa-Hb = 4.6 Hz for 4a and 4.4 Hz for 4a') indicated a gauche relationship of
these two protons in both compounds. For the inherent ring strain imposed by the connecting bridge, only
the aryl-exo-ester endo mode of cycloaddition was possible leading to the observed compounds (Scheme
3). This model of ring formation is also indicative of a concerted rather than a stepwise process, since one
could expect the formation of aryl-exo-ester-exo diastereomers if the latter mechanism was operating. The
relative stereochemistry of the major adduct 4a was deduced from the observation of a strong NOE cross
peak between Hb and Hc in its NOESY spectrum and corroborated by X-ray analysis.10
C6H13
C6H13
NH
O
O
H
N
HN
Hb
N
N
Ha
Bn
MeO2C
C6H13
Hc
CO2Me
O
R3
H
H
N
H
N
O
N
N
CO2Me
Bn
O
O
8a
4a
4a
Phenyl exo, Ester endo
O
H
H
N
O
H
N
H
HN
C6H13
H
N
N
CO2Me
O
Bn
CO2Me
Bn
N
N
C6H13
N
O
C6H13
Bn
MeO2C
N
O
O
8a'
4a'
4a'
Scheme 3. Stereochemistry of the three-component adduct.
Control experiments showed that the observed stereoselectivity was a thermodynamically controlled
process. Indeed, re-submitting the diastereomerically pure compound 4a to the reaction conditions led to
the formation of a mixture of 4a and 4a' with the ratio identical to that resulting from the reaction mixture.
The same is true for 4a’. While the thermo-equilibrium can be interpreted by a sequence of
heterocycloreversion/cycloaddition, the relatively high stability of compound 4 towards fragmentation
and/or degradation was nevertheless intriguing.

HETEROCYCLES, Vol. 73, 2007
733
X
N
O
O
N
O
O
N
MeO2C
H
Bn
MeO2C
PMB
MeO2C
PMB
O
N
N
N
N
H
C6H13
N
H
C6H13
N
C6H13
4a X= O (94%, 3/1)
4b X= CH2 (46%, 4/1)
4d 72% (2/1)
4c 78% (2/1)
O
O
O
N
N
N
MeO2C
Bn
EtO2C
PMB
MeO2C
PMB
O
O
O
Cl
N
N
N
O
O
N
H
C6H13
N
H
N
H
4e (40%)a
4g (64%)a
4f (47%, 2/1)
O
O
O
N
O
N
O
N
O
MeO2C
O
Ph
EtO2C
Bn
MeO2C
PMB
N
N
N
O
Bu
N
H
C6H13
t
O
N
H
C2H4Ph
N
Bn
C2H4Ph
4j 42%a
4h (70%, 3/1)
4i (50%, 3/1)
a
Figure 1. Representative structure of oxa-bridged tetrahydroquinoline 4; only one diastereoisomer was
isolated. Abbreviations: Bn = benzyl; PMB = para-methoxy benzyl.
The scope of this MCR was examined and compounds synthesized are listed in Figure 1. The reaction
conditions have not been individually optimized. As is seen, all substituents at the peripheral of the
tetracyclic ring system can be varied. The α-branched aldehydes, as well as the α-alkyl and α-aryl
substituted α-isocyano acetamides can took part in this reaction. When cyclooctyl aldehyde was used, a
single diastereomer was isolated. Since the nitrogen bearing asymmetric center was the one that
controlled the facial selectivity of the subsequent aza-Diels-Alder cycloaddition, the observation is thus
understandable. However, aromatic aldehyde failed to enter the reaction cascade under these conditions.
The ortho-amino cinnamate having either electron donating or electron withdrawing group at the aromatic
ring participated in the reaction, as did the N-alkylated derivatives. However, the presence of an ester
function was required for the Diels-Alder reaction. Using o-amino styrene 9 as amine input, the oxazole
10 was isolated in 64% yield. Intramolecular cycloaddition did not take place even at refluxing

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HETEROCYCLES, Vol. 73, 2007
temperatrure of toluene (Scheme 4). This result validated on the other hand the reaction sequence that we
proposed for this three-component reaction.
O
NH
CN
LiBr, toluene
60°C
N
+
+
C6H13CHO
C6H13
O
Bn
O
NH2
N
N
1a
2a
9
10
Bn
O
Scheme 4. Three-component synthesis of 5-amino oxazole.
As expected for Ugi type reaction, racemic tetrahydroquinoline was obtained even when enantiomerically
pure isonitrile 1 (R = Bn, or phenyl) was used as input.
Fragmentation of 4 by breaking the aminal function should in principle afford the 4,6-phenanthroline
after oxidative aromatization.16 Two fragmentation pathways are possible leading to amino-substituted
and hydroxylated phenanthroline, respectively. However, under carefully controlled conditions (TFA,
0°C), the oxa-bridge tetracycle 4a was cleanly converted to 4,6-phenanthroline 5a in 71% yield (Scheme
5). Three other phenanthrolines synthesized were listed in the Scheme 5.
O
N
O
O
N
MeO2C
H
Bn
MeO2C
Bn
TFA, MeCN
0°C
N
N
C6H13
N
H
N
C6H13
4a
5a
O
N
O
N
N
MeO2C
PMB
MeO2C
Bn
MeO2C
PMB
Cl
N
N
N
N
C6H13
N
C6H13
N
C6H13
5d (52%)a
5b (30%)
5c (75%)
Scheme 5. Fragmentation of 4a to 5 a Fragmentation was performed at -30°C.
In conclusion, we have developed a novel multicomponent reaction for the synthesis of complex
heterocycles from simple and readily accessible precursors. Besides its synthetic efficiency and potential
application in diversity-oriented synthesis, we demonstrated that Ugi-type condensation can be performed
in toluene in the presence of LiBr without concurrent occurrence of a Passerini-type reaction. Only one
molecule of water was lost in this MCR that leads to the formation of five chemical bonds with current
creation of five asymmetric centers and three heterocycles.

HETEROCYCLES, Vol. 73, 2007
735
EXPERIMENTAL
General procedure for the three-component synthesis of oxa-bridged tetrahydroquinolines (4)
A solution of aniline (3) (1.0 equiv) and aldehyde (2) (1.2 equiv) in dry toluene (0.15 M) with
α-isocyanoacetamide (1) (1.0 equiv) and LiBr (1.0 equiv) was stirred at 60 °C. The reaction was
monitored by TLC (5-20 h). The solvent was removed under reduced pressure and after dilution with
water, the product was extracted with CH2Cl2. The combined organic extracts were washed with brine,
dried over Na2SO4 and evaporated to dryness. Purification of the crude product by either preparative TLC
(silica gel, eluent heptane/AcOEt) or flash chromatography (silica gel, eluent: heptane/AcOEt) afforded
the title compound.
Compound 4a, yield: 94%, dr = 3/1. Major isomer: Yellow crystalline solid, 192-193 °C; IR (CHCl3) ν
3008, 2956, 2926, 2857, 1733, 1628, 1606, 1586, 1495, 1486, 1454, 1437, 1381, 1351, 1302, 1272, 1232,
1168, 1118, 1071, 1047, 1030 cm-1; 1H NMR (400 MHz, CDCl3) δ 0.89 (t, J= 7.0 Hz, 3H), 1.20-1.64 (m,
9H), 1.83-1.94 (m, 1H), 2.60 (ddd, J= 3.2, 5.9, 11.7 Hz, 2H), 2.90 (ddd, J= 3.2, 6.6, 11.9 Hz, 2H), 3.16 (d,
J= 4.6 Hz, 1H), 3.31 (d, J= 4.6 Hz, 1H), 3.60-3.70 (m, 4H), 3.65 (d, J= 16.5 Hz, 1H), 3.80 (s, 3H), 3.82 (d,
J= 16.5 Hz, 1H), 3.89 (dd, J= 3.7, 8.8 Hz, 1H), 3.94 (br s, 1H, NH), 6.62 (dd, J= 1.2, 8.1 Hz, 1H), 6.72
13
(dt, J= 1.2, 7.5 Hz, 1H), 6.96 (td, J= 1.2, 7.7 Hz ), 7.02 (dt, J= 1.2, 7.5 Hz, 1H), 7.20-7.40 (m, 5H); C
NMR (75 MHz, CDCl3) δ 14.2, 22.7, 26.2, 29.5, 29.8, 31.9, 35.8, 47.3, 48.4, 52.0, 52.6, 53.2, 67.1, 97.8,
106.4, 115.6, 119.1, 123.0, 126.9, 127.4, 128.6, 129.3, 129.8, 135.9, 142.7, 171.1, 178.0; MS (ESI) m/z
+
+
+
556 [M+K ], 540 [M+Na ], 518 [M+1]; HRMS (CI) m/z calcd. for: [M+1] 518.30186, m/z found for:
[M+1]+ 518.30170. Minor isomer: Yellow oil; IR (CHCl3) ν 3020, 2956, 2929, 2859, 1729, 1676, 1655,
1
1603, 1494, 1455, 1437, 1379, 1345, 1319, 1302, 1274, 1226, 1218, 1205, 1175, 1116, 1071 cm-1; H
NMR (400 MHz, CDCl3) δ 0.87 (t, J= 6.9 Hz, 3H), 1.25-1.62 (m, 9H), 2.09-2.21 (m, 1H), 2.58 (ddd, J=
3.3, 6.4, 9.7 Hz, 2H), 2.90 (ddd, J= 2.8, 6.4, 9.7 Hz, 2H), 3.15 (d, J= 4.4 Hz, 1H), 3.28 (d, J= 4.4 Hz, 1H),
3.60-3.70 (m, 5H), 3.65 (d, J= 15.1 Hz, 1H), 3.78 (s, 3H), 3.79 (d, J= 15.1 Hz, 1H), 4.18 (d, J= 2.0 Hz,
1H, NH), 6.60 (dd, J= 1.2, 8.0 Hz, 1H), 6.72 (dt, J= 1.2, 7.5 Hz, 1H), 6.95 (dt, J= 1.2, 7.5 Hz ), 7.03 (dt,
13
J= 1.2, 7.5 Hz, 1H), 7.20-7.40 (m, 5H); C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 26.4, 29.2, 29.9, 32.0,
35.7, 44.6, 48.4, 51.6, 52.6, 53.4, 67.2, 98.5, 106.2, 116.1, 118.8, 122.8, 126.9, 127.7, 128.5, 129.5, 129.7,
+
+
135.8, 140.7, 171.1, 178.3; MS (IE) m/z; MS (ESI) m/z 556 [M+K ], 540 [M+Na ], 518 [M+1]; HRMS
(CI) m/z calcd. for: [M+1]+ 518.30186, m/z found for: [M+1]+ 518.30170.
Compound 4b, yield: 46%, dr = 4/1. Major isomer: Yellow oil; IR (CHCl3) ν 3020, 2938, 2854, 1732,
1
1606, 1496, 1348, 1224, 1210, 1219 cm-1; H NMR (300 MHz, CDCl3) δ 0.89 (m, 3H), 1.25-1.57 (m,
15H), 1.87 (m, 1H), 2.58 (m, 2H), 2.92 (m, 2H), 3,16 (d, J= 4.6 Hz, 1H), 3.28 (d, J = 4.6 Hz, 1H), 3.74
(m, 2H), 3.80 (s, 3H), 3.84 (dd, J = 9.1, 3.8 Hz, 1H), 6.61 (d, J = 8.1 Hz, 1H), 6.73 (t, J = 7.6 Hz, 1H),
13
6.96-7.04 (m, 2H), 7.24-7.39 (m, 5H); C NMR (75 MHz, CDCl3) δ 14.1, 22.6, 24.5, 26.1, 26.3 (2C),

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HETEROCYCLES, Vol. 73, 2007
29.4, 29.7, 31.8, 35.6, 47.4, 48.9 (2C), 52.2, 52.4, 53.2, 97.3, 107.3, 115.5, 118.9, 126.6, 127.2, 128.4,
128.2, 129.3, 129.7, 136.3, 142.7, 171.4, 178.8; MS (IE) m/z 430 [M-C6H13]+, 515 [M]+. Minor isomer:
1
Yellow oil; IR (CHCl3) ν 3019, 2933, 2854, 1732, 1606, 1218, 1224, 1211 cm-1; H NMR (300 MHz,
CDCl3) δ 0.86 (m, 3H), 1.25-1.57 (m, 15H), 2.15 (m, 1H), 2,57 (m, 2H), 2.92 (m, 2H), 3.21 (d, J= 4.6 Hz,
1H), 3.25 (d, J= 4.6 Hz, 1H), 3.61 (dd, J=9.1, 3.8 Hz, 1H), 3.66 (d, J= 16.0 Hz, 1H), 3.76 (s, 3H), 3.77 (d,
J= 16.0 Hz, 1H), 6.61 (d, J= 8.1Hz, 1H), 6.74 (t, J= 7.6 Hz, 1H), 6.94-7.04 (m, 2H), 7.21-7.43 (m, 5H);
13C NMR (75 MHz, CDCl3) δ 14.4, 22.9, 24.8, 26.6, 26.4, 29.4, 30.0, 32.2, 35.6, 44.9, 49.3, 51.9, 52.6,
53.6, 98.2, 107.3, 116.2, 118.8, 123.3, 126.8, 127.6, 128.5, 129.6, 129.9, 140.9, 136.4, 171.6, 179.3; MS
(EI) m/z 515 [M]+.
Compound 4c, yield: 78%, dr = 2/1. Major isomer: Yellow oil; IR (CHCl3) ν 3007, 2957, 2929, 2859,
1734, 1655, 1608, 1512, 1487, 1457, 1302, 1249, 1176, 1118, 1035 cm-1; 1H NMR (300 MHz, CDCl3) δ
0.90 (t, J= 7.2 Hz, 3H), 1.20-1.66 (m, 9H), 1.83-1.93 (m, 1H), 2.61 (ddd, J= 3.4, 5.9, 10.2 Hz, 2H), 2.96
(ddd, J= 3.4, 5.9, 11.5 Hz, 2H), 3.11 (d, J= 4.3 Hz, 1H), 3.30 (d, J= 4.7 Hz, 1H), 3.61 (d, J= 14.7 Hz, 1H),
3.64-3.69 (m, 4H), 3.75 (d, J= 14.7 Hz, 1H), 3.79 (s, 3H), 3.81 (s, 3H), 3.89 (dd, J= 3.4, 8.5 Hz, 1H), 3.95
(br s, 1H, NH), 6.63 (d, J= 8.1 Hz, 1H), 6.72 (t, J= 7.5 Hz, 1H), 6.86 (d, J= 8.7 Hz, 2H), 6.95 (d, J= 7.7
Hz, 1H), 7.02 (t, J= 7.5 Hz, 1H), 7.27 (d, J= 8.7 Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 26.2,
29.4, 29.1, 31.9, 34.9, 47.3, 48.4, 52.0, 52.6, 53.2, 55.3, 67.1, 97.7, 106.4, 114.0, 115.6, 119.0, 123.1,
127.4, 127.9, 129.8, 130.3, 142.7, 171.1, 178.2; MS (IE) m/z 547 [M]+. Minor isomer: Yellow oil; IR
(CHCl3) ν 3008, 2957, 2930, 2860, 1697, 1632, 1602, 1511, 1460, 1436, 1320, 1303, 1250, 1170, 1115,
1033 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.87 (t, 3H, J= 6.4 Hz), 1.23-1.60 (m, 9H), 2.03-2.20 (m, 1H),
2.59 (ddd, 2H, J= 3.4, 5.6, 11.9 Hz), 2.96 (ddd, 2H, J= 3.4, 4.7, 11.9 Hz), 3.14 (d, 1H, J= 4.3 Hz), 3.27 (d,
1H, J= 4.3 Hz), 3.58 (d, 1H, J= 16.5 Hz), 3.61 (d, 1H, J= 3.0 Hz), 3.64-3.69 (m, 4H), 3.68 (d, 1H, J= 16.5
Hz), 3.76 (d, 1H, J= 4.3 Hz, NH), 3.79 (s, 3H), 3.80 (s, 3H), 6.60 (d, 1H, J= 8.1 Hz), 6.71 (t, 1H, J= 7.5
Hz), 6.85 (d, 2H, J= 8.7 Hz), 6.94 (d, 1H, J= 7.7 Hz), 7.03 (t, 1H, J= 7.7 Hz), 7.30 (d, 2H, J= 8.7 Hz); 13C
NMR (75 MHz, CDCl3) δ 14.1, 22.7, 26.4, 29.2, 29.8, 32.0, 34.8, 44.6, 48.5, 51.6, 52.6, 53.4, 55.4, 67.2,
98.5, 106.2, 113.9, 114.0, 116.1, 118.8, 122.8, 127.7, 127.8, 129.7, 130.4, 140.7, 171.1, 178.6; MS (IE)
m/z 547 [M]+.
Compound 4d, yield: 72%, dr = 2/1. Major isomer: Yellow oil; IR (CHCl3) ν 3009, 2957, 2929, 2859,
1729, 1604, 1512, 1456, 1438, 1333, 1304, 1253, 1175, 1118, 1033 cm-1; 1H NMR (300 MHz, CDCl3) δ
0.88 (t, J= 6.5 Hz, 3H), 1.25-1.35 (m, 6H), 1.47-1.67 (m, 3H), 2.13-2.18 (m, 1H), 2.19-2.27 (m, 2H),
2.72-2.78 (m, 2H), 3.08 (s, 3H), 3.15 (d, J= 4.3 Hz, 1H), 3.26 (d, J= 4.3 Hz, 1H), 3.40-3.50 (m, 4H),
3.62-3.66 (m, 1H), 3.72-3.77 (m, 2H), 3.80 (s, 3H), 3.88 (s, 3H), 6.62 (d, J= 8.1 Hz, 1H), 6.69 (t, J= 7.4
Hz, 1H), 6.88 (d, J= 8.6 Hz, 2H), 6.94 (d, J= 7.2 Hz, 1H), 7.14 (t, J= 7.2 Hz, 1H), 7.42 (d, J= 8.6 Hz,
2H); 13C NMR (75 MHz, CDCl3) δ 14.2, 22.8, 27.91, 29.6, 30.1, 32.0, 40.4, 45.5, 48.7, 52.6, 53.03, 55.4,

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737
61.8, 66.9, 71.1, 99.0, 105.8, 112.8, 114.1, 117.2, 123.0, 128.0, 129.5, 129.8, 131.2, 142.7, 160.0, 172.1,
181.3. Minor isomer: Yellow oil; IR (CHCl3) ν 3004, 2956, 2928, 2859, 1732, 1603, 1511, 1456, 1437,
1
1339, 1333, 1303, 1273, 1254, 1177, 1119, 1036 cm-1; H NMR (300 MHz, CDCl3) δ 0.87 (t, J= 6.7 Hz,
3H), 1.18-1.28 (m, 6H), 1.42-1.67 (m, 3H), 2.02-2.11 (m, 1H), 2.54-2.61 (m, 2H), 2.87-2.96 (m, 2H),
3.07 (s, 3H), 3.11 (d, J= 4.4 Hz, 1H), 3.28 (d, J= 4.4 Hz, 1H), 3.54-3.71 (m, 7H), 3.78 (s, 3H), 3.80 (s,
3H), 6.61 (d, J= 8.3 Hz, 1H), 6.68 (t, J= 7.5 Hz, 1H), 6.84 (d, J= 8.8 Hz, 2H), 6.94 (d, J= 7.3 Hz, 1H),
7.13 (t, J= 7.3 Hz, 1H), 7.30 (d, J= 8.8 Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 27.8, 29.6, 30.0,
31.9, 34.7, 40.3, 45.0, 48.4, 52.1, 52.5, 55.3, 61.9, 67.1, 98.2, 105.9, 112.6, 113.8, 117.1, 123.5, 127.8,
127.9, 129.5, 130.4, 142.8, 158.5, 171.2, 178.3; MS (IE) m/z 561[M]+; HRMS (IC) m/z calcd. for: [M+1]+
562.3279, m/z found for: [M+1]+ 562.3280.
Compound 4e, yield: 40%, one diastereomer. Yellow oil; IR (CHCl3) ν 3008, 2922, 2857, 2360, 1733,
1671, 1608, 1511, 1486, 1456, 1382, 1355, 1302, 1272, 1248, 1176, 1118, 1036 cm-1; 1H NMR (300 MHz,
CDCl3) δ 1.23-1.30 (m, 4H), 1.49-1.77 (m, 9H), 2.06-2.13 (m, 1H), 2.40-2.44 (br s, 1H), 2.45-2.56 (m,
2H), 2.83-2.93 (m, 2H), 3.09 (d, 1H, J= 4.3 Hz), 3.31 (d, 1H, J= 4.3 Hz), 3.57-3.65 (m, 4H), 3.67 (d, 1H,
J= 11.5 Hz), 3.76 (br s, 1H), 3.79 (s, 3H), 3.82 (s, 4H), 3.84 (d, 1H, J= 11.5 Hz), 6.64 (d, 1H, J= 8.1 Hz),
6.71 (t, 1H, J= 7.5 Hz), 6.83 (d, 2H, J= 8.5 Hz), 6.96 (d, 1H, J= 7.7 Hz), 7.03 (t, 1H, J= 7.5 Hz), 7.29 (d,
13
2H, J= 8.7 Hz); C NMR (75 MHz, CDCl3) δ 24.9, 25.8, 26.6, 26.9, 27.0, 27.2, 27.6, 33.9, 34.8, 36.2,
48.5, 48.6, 52.1, 52.6, 55.4, 59.4, 67.1, 97.9, 106.7, 114.0, 114.0, 115.7, 118.8, 123.0, 127.4, 128.0, 129.9,
130.1, 143.4, 158.6, 171.3, 178.0; MS (IE) m/z 573 [M]+; HRMS m/z calcd. for: [M+1]+ 574.3280, m/z
found for: [M+1]+ 574.3262.
Compound 4f, yield: 47%, dr = 2/1. Major isomer: Yellow solid, 120-122°C; IR (CHCl3) ν 3020, 2974,
2928, 2959, 1735, 1603, 1522, 1493, 1437, 1219, 1118, 1046 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.88 (m,
3H), 1.20-1.57 (m, 9H), 1.87 (m, 1H), 2.60 (m, 2H), 2.96 (m, 2H), 3.09 (d, J= 4.6 Hz, 1H), 3.25 (d, J= 4.6
Hz, 1H), 3.60-3.86 (m, 7H), 3.81 (s, 3H), 6.55 (d, J= 8.5 Hz, 1H), 6.93 (d, J= 2.5 Hz, 1H), 6.96 (dd, J=
8.5, 2.5 Hz, 1H), 7.23-7.34 (m, 5H); 13C NMR (75 MHz, CDCl3) δ 14.0, 22.5, 26.0, 29.3, 29.6, 31.7, 35.7,
46.9, 48.2 (2C), 51.8, 52.6, 53.0, 67.0 (2C), 97.2, 106.3, 116.7, 123.2, 124.4, 126.8, 127.4, 128.5 (2C),
129.2 (3CH), 135.7, 141.3, 170.1, 178. 8; MS (IC) m/z 552 [M]+. Minor isomer: Yellow oil; IR (CHCl3)
1
ν 3019, 2956, 2928, 2858, 1734, 1493, 1455, 1218, 1118 cm-1; H NMR (300 MHz, CDCl3) δ 0.86 (m,
3H), 1.14-1.59 (m, 9H), 2.16 (m, 1H), 2.58 (m, 2H), 2.92 (m, 2H), 3.12 (d, J= 4.6 Hz, 1H), 3.23 (d, J= 4.6
Hz, 1H), 3.60-3.83 (m, 7H), 3.78 (s, 3H), 6.52 (d, J= 8.5 Hz, 1H), 6.91 (d, J= 2.5 Hz, 1H), 6.97 (dd, J=
8.5, 2.5 Hz, 1H), 7.23-7.37 (m, 5H); 13C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 26.4, 29.2, 29.8, 32.0, 35.7,
46.3, 48.5 (2C), 51.5, 52.7, 53.3, 67.1 (2C,), 98.1, 106.2, 117.2, 123.0, 124.3, 126.9, 127.8, 128.5 (2C),
129.3, 129.5, 135.7, 139.4, 170.7, 178.6.

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Compound 4g, yield: 64%, one diastereomer. Yellow oil; IR (CHCl3) ν 3395, 3032, 3008, 2897, 2860,
1
1734, 1630, 1611, 1512, 1484, 1455, 1380, 1353, 1301, 1272, 1249, 1176, 1118, 1040 cm-1; H NMR
(300 MHz, CDCl3) δ 1.32 (d, 3H, J= 76.4 Hz), 2.61-2.69 (m, 2H), 2.92-3.01 (m, 2H), 3.05 (d, 1H, J= 4.7
Hz), 3.19 (d, 1H, J= 4.7 Hz), 3.61 (d, 1H, J= 16.8 Hz), 3.63-3.72 (m, 5H), 3.72 (d, 1H, J= 16.8 Hz), 3.77
(d, 1H, J= 5.1 Hz), 3.79 (s, 3H), 3.80 (s, 3H), 5.84 (dd, 2H, J= 1.3, 3.3 Hz), 6.17 (s, 1H), 6.45 (s, 1H),
13
6.86 (d, 2H, J= 8.7 Hz), 7.25 (d, 2H, J= 8.7 Hz); C NMR (75 MHz, CDCl3) δ 15.5, 35.0, 47.4, 48.3,
49.3, 52.0, 52.6, 55.3, 67.1, 97.4, 97.6, 100.7, 106.2, 108.6, 112.5, 113.9, 114.0, 115.0, 127.8, 130.3,
130.4, 137.6, 141.2, 146.9, 158.5, 171.0, 178.8; MS (IE) m/z 521 [M]+; HRMS (EI) m/z calcd. for:
[M+1]+ 521.21618, m/z found for: [M+1]+ 521.21721.
Compound 4h, yield: 70%, dr = 3/1. Major isomer: Yellow oil; IR (CHCl3) ν 3391, 3032, 3009, 2921,
2859, 1728, 1631, 1602, 1505, 1483, 1455, 1372, 1336, 1302, 1272, 1256, 1236, 1179, 1118, 1041 cm-1;
1H NMR (300 MHz, CDCl3) δ 1.36 (t, 3H, J= 7.4 Hz), 1.83-1.96 (m, 1H), 2.19-2.29 (m, 1H), 2.58-2.66
(m, 2H), 2.85 (t, 2H, J= 8.1 Hz), 2.93-3.01 (m, 2H), 3.03 (d, 1H, J= 4.4 Hz), 3.23 (d, 1H, J= 4.4 Hz),
3.56-3.73 (m, 4H), 3.38 (d, 1H, J= 16.2 Hz), 3.78 (d, 1H, J= 5.1 Hz), 3.83 (d, 1H, J= 16.2 Hz), 3.88 (dd,
1H, J= 3.7, 8.8 Hz), 4.16-4.39 (m, 2H), 5.84 (d, 2H, J= 2.9 Hz), 6.06 (s, 1H), 6.45 (s, 1H), 7.22-7.34 (m,
10 H); 13C NMR (75 MHz, CDCl3) δ 14.4, 33.7, 33.0, 36.0, 47.4, 48.4, 52.0, 53.6, 61.5, 67.1, 97.7, 97.6,
100.7, 106.3, 108.5, 114.9, 126.3, 126.9, 128.4, 128.6, 128.7, 129.4, 135.9, 137.4, 141.2, 141.7, 146.9,
170.5, 178.3; MS (IC) m/z 594 [M-H]+. Minor isomer: Yellow oil; IR (CHCl3) ν 3397, 3032, 3009, 2922,
2859, 1728, 1631, 1602, 1505, 1483, 1455, 1372, 1329, 1304, 1272, 1256, 1236, 1176, 1118, 1041 cm-1;
1H NMR (300 MHz, CDCl3) δ 1.34 (t, 3H, J= 7.1 Hz), 1.80-1.95 (m, 1H), 2.45-2.53 (m, 1H), 2.55-2.64
(m, 2H), 2.82 (t, 2H, J= 8.1 Hz), 2.92-3.00 (m, 2H), 3.05 (d, 1H, J= 4.6 Hz), 3.16 (d, 1H, J= 4.6 Hz),
3.58-3.73 (m, 6H), 3.64 (d, 1H, J= 16.4 Hz), 3.80 (d, 1H, J= 16.4 Hz), 4.08-4.35 (m, 2H), 5.84 (s, 2H),
5.97 (s, 1H), 6.43 (s, 1H), 7.18-7.37 (m, 10 H); 13C NMR (75 MHz, CDCl3) δ 14.4, 30.7, 33,1, 35.8, 44.7,
48.4, 51.4, 53.1, 61.5, 67.2, 98.1, 98.4, 100.7, 106.0, 108.5, 114.7, 126.1, 126.8, 128.5, 128.6, 128.7,
129.5, 135.1, 135.8, 141.0, 141.7, 147.0, 170.5, 178.3; MS (IE) m/z 595 [M]+.
Compound 4i, yield: 50%, dr = 3/1. Major isomer: Yellow oil; IR (CHCl3) ν 3024, 2958, 2928,
1
2858,1735, 1496, 1265, 1228, 1119 cm-1; H NMR (300 MHz, CDCl3) δ 0.94 (m, 3H), 1.31-1.74 (m,
18H), 2.01 (m, 1H), 2.76 (m, 2H), 3.15 (m, 2H), 3.31 (d, J= 4.4 Hz, 1H), 3.49 (s, 3H), 3.52 (d, J= 4.4 Hz,
1H), 3.72 (m, 4H), 4.01 (dd, J= 8.8, 3.0 Hz, 1H), 6.66 (d, J= 8.6 Hz, 1H), 6.70 (d, J= 3.1 Hz, 1H), 6.77
(dd, J= 8.7, 2.6 Hz, 1H), 6.85 (d, J= 8.9 Hz, 2H), 7.30 (d, J= 8.8 Hz, 2H), 7.38-7.46 (m, 3H), 8.19 (dd, J=
13
8.1, 1.7 Hz, 2H); C NMR (75 MHz, CDCl3) δ 14.1, 22.6, 26.1, 29.3, 29.7, 31.5 (3C), 31.7, 34.2, 46.4,
47.9, 51.8, 52.1, 53.4, 66.9 (2C), 97.0, 106.5, 116.5, 116.6 (2C), 119.4, 121.1, 124.3, 126.3 (2C), 127.
(2C), 128.3 (2C), 131.3, 131.8, 139.0, 144.9, 148.8, 156.3, 169.8, 171.5; MS (ESI) m/z 566 [M-C4H8NO]+,
567 [M-C6H13]+, 651 [M]+, 652 [M+H]+. Minor isomer: Yellow oil; IR (CHCl3) ν 3009, 2961, 2928,

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739
2858,1736, 1497, 1271, 1251, 1232, 1119 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.90 (m, 3H), 1.20-1.61 (m,
18H), 2.30 (m, 1H), 2.75 (m, 2H), 3.12 (m, 2H), 3.34 (d, J= 4.3 Hz, 1H), 3.47 (d, J= 4.3 Hz, 1H),
3.61-3.82 (m, 4H), 3.78 (s, 3H), 4.26 (m, 1H), 6.60 (d, J= 8.6 Hz, 1H), 6.66 (d, J= 2.6 Hz, 1H), 6.75 (dd,
J= 8.0, 2.6 Hz, 1H), 6.85-6.91 (m, 2H), 7.27-7.46 (m, 4H), 7.94 (d, J= 8.2 Hz, 1H), 8.19 (d, J= 6.5 Hz,
13
2H); C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 25.1, 26.4, 27.3, 28.1, 29.2, 31.6, 31.9, 34.3, 35.5, 48.1,
50.5, 52.3, 56.6, 63.4, 65.1, 67.0, 72.5, 94.6, 94.8, 101.3, 106.3, 108.2, 116.8, 119.5, 126.0, 126.4, 127.3,
128.4, 131.4, 131.9, 141.5, 147.8, 152.3, 169.9, 172.0.
Compound 4j, yield: 42%, one diastereomer. Yellow oil; IR (CHCl3) ν 3065, 3032, 3009, 2956, 2860,
1
2360, 1733, 1602, 1512, 1498, 1454, 1382, 1355, 1272, 1249, 1177, 1118, 1071, 1030 cm-1; H NMR
(300 MHz, CDCl3) δ 1.85-2.07 (m, 2H), 2.43-2.55 (m, 1H), 2.57-2.68 (m, 2H), 2.80-2.87 (m, 1H),
2.92-3.01 (m, 2H), 3.16 (d, 1H, J= 4.3 Hz), 3.38 (d, 1H, J= 4.3 Hz), 3.58 (d, 1H, J= 16.7 Hz), 3.67-3.75
(m, 8H), 3.80 (s, 3H), 3.81 (d, 1H, J= 16.7 Hz), 4.39 (d, 1H, J= 16.2 Hz), 4.77 (d, 1H, J= 16.2 Hz), 6.57
(d, 1H, J= 8.1 Hz), 6.67 (t, 1H, J= 7.2 Hz), 6.86 (d, 2H, J= 8.7 Hz), 6.96 (d, 1H, J= 7.2 Hz), 7.00 (t, 1H,
13
J= 7.6 Hz), 7.13-7.27 (m, 8H), 7.30 (d, 2H, J= 8.7 Hz) 7.40 (d, 2H, J= 7.2 Hz); C NMR (75 MHz,
CDCl3) δ 29.4, 31.7, 33.3, 34.8, 34.8, 45.1, 48.9, 52.2, 52.6, 55.3, 56.5, 60.3, 67.0, 98.7, 105.9, 113.8,
114.3, 117.6, 124.1, 125.9, 127.0, 127.4, 127.7, 128.4, 128.5, 128.5, 129.6, 130.5, 139.0, 141.5, 141.9,
158.5, 171.1, 178.4; MS (ESI) m/z 658 [M+H]+, 680 [M+Na]+.
Compound 10, yield: 64%. Yellow oil; IR (CHCl3) ν 3016, 2960, 2929, 2860, 1602, 1508, 1454, 1234,
1225, 1114cm-1; 1H NMR (300 MHz, CDCl3) δ 0.80 (t, J= 7.1 Hz, 3H), 1.24 (m, 8H), 1.95 (q, J= 6.6 Hz,
2H), 2.92 (t, J= 4.4 Hz, 4H), 3.70 (t, J= 4.4 Hz, 4H), 3.82 (s, 2H), 4.52 (t, J= 6.6 Hz, 1H), 5.36 (dd, J=
11.0, 2.0 Hz, 1H), 5.63 (dd, J= 17.6, 2.0 Hz, 1H), 6.75 (m, 2H), 6.84 (dd, J= 17.6, 11.0 Hz, 1H), 6.75 (m,
2H), 7.11-7.28 (m, 5H); 13C NMR (75 MHz, CDCl3) δ 14.1, 22.6, 25.8, 29.0, 31.7 (2C), 34.7, 51.1 (2C),
53.1, 66.9 (2C), 112.5, 116.6, 118.3, 124.5, 125.2, 126.2, 127.6, 128.4 (4C), 128.9, 133.0, 139.5, 144.1,
151.9, 159.9; MS (IE) m/z 459 [M]+, 460 [M+H]+.
General procedure for the synthesis of 4,6-diazaphenanthrene (5): A solution of
epoxy-tetrahydroquinoline (4) (15.0 mg, 0.029 mmol, 1.0 equiv.) in MeCN (0.30 mL) was cold at 0 °C
then TFA (2.0 µL, 0.029 mmol, 1.0 equiv.) was added and the reaction mixture was stirred at 0°C for 2 h
to 3h. After dilution with saturated aqueous solution of NaHCO3, the product was extracted with CH2Cl2.
The combined organic extracts were washed with brine, dried over Na2SO4 and the solvent was removed
under reduced pressure. The crude was purified by preparative TLC (silica gel, eluent heptane/AcOEt ).
Compound 5a. Yellow solid; 216-217 °C; yield: 71%; IR (CHCl3) ν 2956, 2930, 2858, 1732, 1603, 1454,
1435, 1380, 1265, 1146, 1111 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.88 (t, 3H, J= 7.0 Hz), 1.26-1.33 (m,
4H), 1.40 (q, 2H, J= 8.1 Hz), 1.74 (q, 2H, J= 8.1 Hz), 2.99 (m, 2H), 3.30 (m, 2H), 3.40 (t, 2H, J= 8.1 Hz),
3.69 (m, 2H), 3.83 (m, 2H), 4.14 (s, 3H), 4.48 (s, 2H), 7.23 (m, 5H), 7.55 (ddd, 1H, J= 1.4, 7.0, 8.5 Hz),

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HETEROCYCLES, Vol. 73, 2007
7.72 (ddd, 1H, J= 1.4, 7.2, 8.1 Hz), 8.09 (dd, 1H, J= 1.0, 7.6 Hz), 8.14 (dd, 1H, J= 1.0, 8.1 Hz); 13C NMR
(75 MHz, CDCl3) δ 14.2, 22.7, 29.8, 29.8, 31.9, 35.6, 41.5, 51.1, 53.2, 67.9, 121.7, 123.3, 123.6, 126.6,
126.6, 128.5, 129.3, 129.4, 130.3, 138.7, 138.8, 139.0, 143.2, 144.5, 160.3, 165.1, 169.8; MS (IE) m/z 497
[M]+, 498 [M+H]+.
Compound 5b. Yellow solid, 123-126 °C; yield: 30%; IR (CHCl3) ν 3020, 2933, 2855, 1731, 1512, 1453,
1
1434, 1265, 1247, 1231, 1214, 1201 cm-1; H NMR (300 MHz, CDCl3) δ 0.89 (t, J= 6.7 Hz, 3H),
1.26-1.40 (m, 6H), 1.62-1.73 (m, 6H), 2.37 (m, 2H), 3.10 (m, 4H), 3.42 (t, J= 7.8 Hz, 2H), 3.80 (s, 3H),
4.11 (s, 3H), 4.37 (s, 2H), 6.86 (d, J= 10.0 Hz, 2H), 7.26 (d, J= 10.0 Hz, 2H), 7.54 (t, J= 7.7 Hz, 1H),
7.71 (t, J= 7.7 Hz, 1H), 8.11 (m, 2H); MS (ESI) m/z 526 [M+H]+.
Compound 5c. Yellow solid, 153-154 ˚C; yield: 75%; IR (CHCl3) ν 2956, 2931, 2858, 1732, 1603, 1511,
1455, 1435, 1380, 1265, 1248, 1177, 1111, 1036 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.88 (t, 3H, J= 6.7
Hz), 1.27-1.32 (m, 4H), 1.42 (q, 2H, J= 7.7 Hz), 1.76 (q, 2H, J= 7.8 Hz), 2.98 (m, 2H), 3.33 (m, 2H), 3.42
(t, 2H, J= 7.9 Hz), 3.71 (m, 2H), 3.79 (s, 3H), 3.85 (m, 2H), 4.13 (s, 3H), 4.41 (s, 2H), 6.86 (d, 2H, J= 8.3
Hz), 7.22 (d, 2H, J= 8.3 Hz), 7.55 (t, 1H, J= 7.1 Hz), 7.72 (t, 1H, J= 6.9 Hz), 8.08 (d, 1H, J= 8.1 Hz),
13
8.14 (d, 1H, J= 7.1 Hz); C NMR (75 MHz, CDCl3) δ 14.27, 22.79, 29.81, 29.93, 31.98, 35.65, 40.64,
51.10, 53.18, 55.38, 68.00, 113.89, 121.78, 123.69, 126.69, 128.75, 129.29, 130.36, 130.73, 133.89,
138.83, 139.11, 139.18, 143.14, 144.54, 160.66, 165.10, 169.87; MS (ESI) m/z 528 [M+H]+; HRMS (IC)
m/z calcd. for: [M+1]+ 528.2854, m/z found for: [M+1]+ 528.2862.
Compound 5d. Yellow solid; 120-122 °C; yield: 52%; IR (CHCl3) ν 3014, 2958, 2929, 2858, 1734, 1452,
1
1434, 1265, 1111 cm-1; H NMR (300 MHz, CDCl3) δ 0.83 (t, J = 6.8 Hz, 3H), 1.15-1.29 (m, 4H),
1.34-1.38 (m, 2H), 1.68 (q, J = 7.8 Hz, 2H), 2.97 (m, 2H), 3.23 (m, 2H), 3.33 (t, J= 7.8 Hz, 2H),
3.71-3.77 (m, 4H), 4.12 (s, 3H), 4.43 (s, 2H), 7.22-7.28 (m, 5H), 7.62 (dd, J= 8.5, 2.0 Hz, 1H), 7.98 (d, J
= 2.0 Hz, 1H), 8.02 (d, J = 8.5 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 14.2, 22.7, 29.6, 29.8, 31.9, 35.5,
41.5, 51.1 (2C), 53.3, 67.9 (2C), 122.4, 122.7, 123.5, 126.6, 128.5 (2C), 129.4 (2C), 129.7, 131.6, 132.4,
138.5, 138.6, 139.0, 143.0, 143.4, 161.2, 165.4, 169.4; MS (ESI) m/z 532 [M]+.
ACKNOWLEDGEMENT
We thank financial support from CONACYT (E. G-Z.) and CNRS. A doctoral fellowship from the
“Ministère de l’Enseignement Supérieur et de la Recherche” to A. F. are gratefully acknowledged.
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