Total synthesis of the fumiquinazoline alkaloids: Solution-phase studies

Article abstract of DOI:10.1021/jo9914364

Biomimetic total syntheses of glyantrypine, fumiquinazoline F, fumiquinazoline G, and fiscalin B were achieved in four steps from tryptophan methyl ester. In the key step, the anthranilamide residue in a linear tripeptide is dehydrated to a benzoxazine by reaction with triphenylphosphine, iodine, and a tertiary amine. The benzoxazines subsequently undergo rearrangement to the natural products via an amidine intermediate. This dehydrative oxazine to quinazoline route is applicable to a broad range of N-acylanthranilamides, including sterically hindered cases.

Full text of DOI:10.1021/jo9914364

1022
J . Org. Chem. 2000, 65, 1022-1030
Tota l Syn th esis of th e F u m iqu in a zolin e Alk a loid s: Solu tion -P h a se
Stu d ies1
Haishan Wang and A. Ganesan*,†
Institute of Molecular and Cell Biology, National University of Singapore,
30 Medical Drive, Singapore 117609
Received September 13, 1999
Biomimetic total syntheses of glyantrypine, fumiquinazoline F, fumiquinazoline G, and fiscalin B
were achieved in four steps from tryptophan methyl ester. In the key step, the anthranilamide
residue in a linear tripeptide is dehydrated to a benzoxazine by reaction with triphenylphosphine,
iodine, and a tertiary amine. The benzoxazines subsequently undergo rearrangement to the natural
products via an amidine intermediate. This dehydrative oxazine to quinazoline route is applicable
to a broad range of N-acylanthranilamides, including sterically hindered cases.
The elements of anthranilic acid and tryptophan are
incorporated into a variety of fungal quinazoline metabo-
lites,2 many of which display significant biological activ-
ity. Recently, four examples were isolated in which the
quinazoline skeleton is fused onto a third amino acid in
diketopiperazine-like fashion: glyantrypine (1, Figure 1)
from Aspergillus clavatus,3 fumiquinazolines F (2) and
G (3) from Aspergillus fumigatus,4 and fiscalin B (4) from
Neosartorya fischeri and Corynascus setosus.5
We were interested in a concise synthetic route to the
tricyclic core of these alkaloids, which may be viewed as
one of Nature’s solutions for the display of amino acid
side-chains in a peptidomimetic scaffold. The fumiquinazo-
lines are cytotoxic against the P388 leukemia cell line,
while fiscalin B is a substance P antagonist, suggesting
that analogues based on this template might result in
novel biologically active compounds. Furthermore, a
synthesis of these natural products would also pave the
way toward more complex members in this series, which
feature further oxidative transformations of the indole
and quinazoline rings. Here, we describe our efforts6
culminating in the total synthesis of 1-4. Our route has
also been translated7 to solid-phase conditions for the
parallel array synthesis of analogues.
F igu r e 1.
* To whom correspondence should be addressed.
Resu lts a n d Discu ssion
† Present address: Department of Chemistry, University of
Southampton, Southampton SO17 1BJ , United Kingdom. Tel: +44
2380 593897. Fax: +44 2380 596805. E-mail: ganesan@soton.ac.uk.
(1) Abbreviations: Ala ) Alanine, EDC ) 1-ethyl-3-(3-(diethylamino)-
propyl)carbodiimide‚HCl, Fmoc ) (9H-fluoren-9-ylmethoxy)carbonyl,
Gly ) glycine, Phe ) phenylalanine, PyBrOP ) bromo-tris-pyrrolidi-
nophosphonium hexafluorophosphate, Trp ) tryptophan, Val ) valine.
(2) For recent reviews, see (a) Michael, J . P. Nat. Prod. Rep. 1998,
15, 595-606. (b) J ohne, S. In Rodd’s Chemistry of Carbon Compounds
(Supplements to the 2nd edition); Ansell, M. F., Ed.; Elsevier: Am-
sterdam, 1995; Vol. IV I/J , pp 223-240.
Our retrosynthesis of fumiquinazoline G was based on
a possibly biomimetic dehydration of tripeptide 5 (Figure
2). While the regioselectivity was open to question, we
believed it would occur in the desired sense due to the
differential bias imparted by the anthranilate. Thus, only
one amide NH involves an aniline instead of an aliphatic
amine, and similarly only one amide involves a benzoic
acid instead of an aliphatic carboxylate. Another ret-
rosynthetic candidate was 6, which differs from 5 in the
timing of ring formation: quinazoline dehydration first,
followed by diketopiperazine-like cyclization. This alter-
native appeared synthetically more tractable. In addition,
this route proceeds via two six-membered ring closures,
rather than an entropically more demanding macrocyclic
intermediate as in 5. Soon after we had set the synthesis
of linear tripeptide 6 as our immediate goal, a total
(3) Penn, J .; Mantle, P. G.; Bilton, J . N.; Sheppard, R. N. J . Chem.
Soc., Perkin Trans 1 1992, 1495-1496.
(4) (a) Numata, A.; Takahashi, C.; Matsushita, T.; Miyamoto, T.;
Kawai, K.; Usami, Y.; Matsumura, E.; Inoue, M.; Ohishi, H.; Shingu,
T. Tetrahedron Lett. 1992, 33, 1621-1624. (b) Takahashi, C.; Mat-
sushita, T.; Doi, M.; Minoura, K.; Shingu, T.; Kumeda, Y.; Numata, A.
J . Chem. Soc., Perkin Trans. 1 1995, 2345-2353.
(5) (a) Wong, S.-M.; Musza, L. L.; Kydd, G. C.; Kullnig, R.; Gillum,
A. M.; Cooper, R. J . Antibiot. 1993, 46, 545-553. (b) Fujimoto, H.;
Negishi, E.; Yamaguchi, K.; Nishi, N.; Yamazaki, M. Chem. Pharm.
Bull. 1996, 44, 1843-1848.
(6) (a) Communication: Wang, H.; Ganesan, A. J . Org. Chem. 1998,
63, 2432-2433. (b) Portions of this work were presented by H. Wang
at the 12th International Conference on Organic Synthesis, Venezia,
Italy, J un 28-J ul 2, 1998.
(7) Wang, H.; Ganesan, A. J . Comb. Chem. 2000, 2, in press.
10.1021/jo9914364 CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/29/2000

Total Synthesis of the Fumiquinazoline Alkaloids
J . Org. Chem., Vol. 65, No. 4, 2000 1023
Sch em e 1a
a
Reagents and conditions: (a) Fmoc-D-Ala-Cl (1.2 equiv), CH2Cl2/aq Na2CO3, rt, 1 h, 86%; (b) Ph3P (5.0 equiv), I2 (4.9 equiv), EtN-
(i-Pr)2 (10.1 equiv), rt, 2.5 h, 65%; (c) (i) 20% piperidine in CH2Cl2, rt, 12 min; (ii) MeCN, reflux 1.5 h, 78.5%; (d) Fmoc-L-Val-Cl (1.4
equiv), CH2Cl2/aq Na2CO3, rt, 2 h, 90%; (e) Ph3P (5.0 equiv), I2 (4.9 equiv), EtN(i-Pr)2 (10.4 equiv), rt, 8 h, 82%; (f) (i) 20% piperidine in
CH2Cl2, rt, 12 min; (ii) MeCN, DMAP (1.3 equiv), reflux 19 h, 72%.
mann conditions proceeded smoothly to yield 6. Previous
protocols13 for the transformation of linear peptides such
as 6 to quinazolines are highly susceptible to steric
hindrance around the cyclizing amide groups and un-
likely to work with our compound.14 Thus, we anticipated
having to survey a broad range of dehydrating reagents.
In the event, this proved to be unnecessary. Our first trial
was a Ph3P/I2/tertiary amine combination recently used
by Wipf15 to dehydrate â-keto amides to oxazoles. Since
the acidity of our anthranilamide would approximate a
ketone, we tested these conditions with our substrate.
Provided a large excess of reagents was used, a major
product was obtained in good yield (later identified as
oxazine 9, vide infra), which upon treatment with 20%
piperidine in dichloromethane afforded the natural prod-
uct (-)-fumiquinazoline G (3). In addition, a small
amount (5%) of the trans epimer (i.e., fumiquinazoline
F, 2) was obtained. The optical activity of this material
was almost zero, indicating that either chiral center is
equally capable of epimerization. The extent of formation
of 2 places an upper limit for a single epimerization event,
while the probability of both centers racemizing simul-
taneously to contaminate 3 with its enantiomer is
significantly lower.16
F igu r e 2.
synthesis of ent-fumiquinazoline G was reported8 which
involved disconnection to 7, i.e., annulation of the quinazo-
line onto a diketopiperazine. In practice, the aza-Wittig
reaction used required significant protecting group ma-
nipulation, and the overall synthesis takes 12 steps from
Cbz-L-tryptophan.
The direct coupling of D-tryptophan methyl ester9 with
anthranilic acid mediated by EDC10 gave dipeptide 8 in
93% yield (Scheme 1).11 Condensation of 8 and Fmoc-D-
alanine with PyBroP as acylating agent occurred in only
35% yield; instead, use of the more reactive Fmoc-D-
alanine acid chloride12 under two-phase Schotten-Bau-
For the synthesis of fiscalin B, we coupled 8 with Fmoc-
L-valine acid chloride to yield tripeptide 10. Following
Ph3P/I2 dehydration to oxazine 11 and Fmoc deprotection
by piperidine, an analogous cyclization to the natural
product did not occur at room temperature, either in
solution or during silica purification. The solvent was
(8) He, F.; Snider, B. B. Synlett 1997, 483-484.
(9) In our initial studies, we used the cheaper L-amino acids, leading
to the total synthesis of ent-fumiquinazoline G, which is summarized
in the Experimental Section.
(13) For example, see: (a) Bu¨chi, G.; DeShong, P. R.; Katsumura,
S.; Sugimura, Y. J . Am. Chem. Soc. 1979, 101, 5084-5086. (b)
Ohnuma, T.; Kimura, Y.; Ban, Y. Tetrahedron Lett. 1981, 22, 4969-
4972. (c) Nakagawa, M.; Taniguchi, M.; Sodeoka, M.; Ito, M.; Yamagu-
chi, K.; Hino, T. J . Am. Chem. Soc. 1983, 105, 3709-3710.
(14) He and Snider (ref 8) were unsuccessful with such reactions
on a similar peptide, although details are not given.
(15) Wipf, P.; Miller, C. P. J . Org. Chem. 1993, 58, 3604-3606.
(16) We did not observe any enantiomer by NMR analysis with
chiral lanthanide shift reagents (detection limit of 2% from control
experiments).
(10) (a) Boojamra, C. G.; Burow, K. M.; Ellman, J . A. J . Org. Chem.
1995, 60, 5742-5743. (b) Boojamra, C. G.; Burow, K. M.; Thompson,
L. A.; Ellman, J . A. J . Org. Chem. 1997, 62, 1240-1256.
(11) Alternatively, tryptophan methyl ester was refluxed with isatoic
anhydride in 1,2-dichloroethane to give 8 in 93% yield.
(12) Carpino, L. A.; Cohen, B. J .; Stephens, K. E., J r.; Sadat-Aalaee,
S. Y.; Tien, J .-H.; Langridge, D. C. J . Org. Chem. 1986, 51, 3732-
3734.

1024 J . Org. Chem., Vol. 65, No. 4, 2000
Wang and Ganesan
Sch em e 2a
evaporated off, and the residues were washed with
hexanes to remove the dibenzofulvene-piperidine ad-
duct. Refluxing the residue overnight in toluene/triethyl-
amine (40:1) gave 36% of fiscalin B (4). The yield was
significantly improved by switching to a more polar
solvent: refluxing in acetonitrile with DMAP for 19 h
afforded fiscalin B in 72% yield (49% overall for the four
steps from D-tryptophan methyl ester).
In these sequences, we originally believed the Ph3P/
I2/tertiary amine dehydration of 6 and 10 resulted in a
quinazoline, while the subsequent piperidine treatment
would release a free amine which cyclizes to the natural
product. However, in the fiscalin B series, there were
significant differences in 15N chemical shift between 11
and model quinazolines. Attempted silica purification
after Fmoc deprotection yielded only linear tripeptide 10
with the Fmoc group removed, while refluxing the crude
material in methanol with 1.3 equiv of DMAP for 60 h
gave 23% of a ring-opened methanol adduct identified
as imino ether 12 as well as 40% of fiscalin B. All these
results are consistent with the Ph3P/I2/tertiary amine
dehydration producing a relatively unstable oxazine as
in an earlier publication17 by Mazurkiewicz. Meanwhile,
both the Snider and Hart groups have independently
repeated18 our quinazoline synthesis, and Snider has
demonstrated the mechanism (eq 1) for the conversion
of the initially formed oxazine to the quinazoline upon
piperidine treatment.
a
Reagents and conditions: (a) Fmoc-NH(R)CHCOCl, CH2Cl2/
aq Na2CO3, rt; (b) Ph3P, I2, EtN(i-Pr)2, rt; (c) 20% piperidine in
CH2Cl2, rt; (d) MeCN, reflux.
erazine cyclizations. With hindsight, this selection turned
out to be crucial for success, as only a deprotection
scheme using a nucleophilic amine would have caused
ring-opening of the oxazine to the amidine. The oxazine-
quinazoline rearrangement was mediated by silica in
Snider’s case, and a trimethylaluminum-thiophenolate
complex in Hart’s. We find that heating20 of the piperi-
dine amidine is sufficient to effect this reaction, as in the
fiscalin B synthesis described above. The synthesis of
fumiquinazoline G (3) was also repeated with thermal
cyclization for the last step. Refluxing the crude amidine
in acetonitrile for 1.5 h with DMAP resulted in almost
complete conversion to 3. We then found that the addition
of DMAP was not required; refluxing in acetonitrile alone
for 1.5 h afforded 3 in 78.5% yield, together with 4.7% of
racemized 2. Similarly, we have also synthesized the
natural products (-)-glyantrypine21 (1), fumiquinazoline
F22 (2), and an unnatural analogue 15 with a phenyl-
alanine side-chain (Scheme 2). Overall yields for 1, 2, and
15 from D-tryptophan methyl ester were 71, 37, and 61%
respectively.
Our oxazine-quinazoline synthesis was also tested
with simple amides 16a -d (Scheme 3). With oxazine 17a ,
Our choice of the Fmoc protecting group was based on
its extensive use in solution- and solid-phase peptide
synthesis and the ease of formation of stable amino acid
chlorides, as well as our past experience19 in diketopip-
(20) Although we use a neutral solvent, it is possible that the
reaction is catalyzed by the piperidine byproduct released.
(21) The absolute configuration of the natural product was not
assigned, and we were unable to obtain a sample.
(17) Mazurkiewicz, R. Monatsh. Chem. 1989, 120, 973-980.
(18) (a) He, F.; Snider, B. B. J . Org. Chem. 1999, 64, 1397-1399.
(b) Hart, D. J .; Magomedov, N. Tetrahedron Lett. 1999, 40, 5429-5432.
(19) (a) Wang, H.; Ganesan, A. Tetrahedron Lett. 1997, 38, 4327-
4328. (b) Wang, H.; Ganesan, A. Org. Lett. 1999, 1, 1647-1649.
(22) For both fumiquinazoline F and fiscalin B, the melting point
and optical rotation for our synthetic material is significantly higher
than reported for the natural product, probably reflecting the difficulty
of purifying the limited amount isolated and obtaining accurate
measurements.

Total Synthesis of the Fumiquinazoline Alkaloids
J . Org. Chem., Vol. 65, No. 4, 2000 1025
Sch em e 3
piperidine treatment gave a mixture of piperidine ami-
dine, quinazoline 18a , and decomposition back to aceta-
mide 16a in a 86:8:6 ratio. Refluxing this crude mixture
in 1:1 acetonitrile/1,2-dichloroethane for 15 h resulted in
93% yield of quinazoline 18a , with 5% of acetamide 16a
recovered. Instead, reaction of the crude mixture under
Snider-type conditions (silica, EtOAc/CH2Cl2/MeOH 67:
20:13, rt 15 h) only gave a 61:33:6 mixture of amidine,
18a , and 16a , respectively.
Only the extremely hindered pivalamide 16d did not
provide a satisfactory yield of oxazine 17d with our usual
Ph3P/I2 protocol at room temperature. Carrying out the
reaction in refluxing dichloroethane resulted in formation
of a fluorescent compound, identified as â-carboline 19
(eq 2). Under these harsher conditions, Bischler-
Napieralski-like electrophilic substitution of the indole
apparently becomes the major pathway, and the resulting
dihydro-â-carboline further aromatized to 19. The only
other limitation we have encountered in our oxazine-
forming reaction is with primary amides. In a projected
synthesis of luotonin A (eq 3), treatment of diamide 2023
under our dehydrating conditions yielded nitrile 21. The
ability of Ph3P/I2 combinations to dehydrate primary
amides to nitriles is precedented,24 and is presumably too
facile for the oxazine cyclization25 to compete.
activity and also show that fiscalin B, previously reported
only as a substance P antagonist, has cytotoxic activity.
Su m m a r y
Dehydration of anthranilamides features in a number
of secondary metabolite biosynthetic pathways, such as
the fumiquinazolines as well as compounds like the
cholecystokinin antagonist asperlicin and the multidrug-
resistance reversing agent ardeemin. For the first time,
we have devised a general and mild procedure with
simple reagents for accomplishing such dehydrations via
oxazine intermediates. The power of this approach has
resulted in biomimetic total syntheses of 1-4 which are
nearly ideal in terms of step efficiency. It is difficult to
imagine assembling a linear tripeptide and performing
two intramolecular cyclizations in less than the four
chemical operations we have taken. Two other groups
have already incorporated our methodology for their own
synthetic targets.
Exp er im en ta l Section
We screened our quinazolines in filter disk antibacte-
rial (tested strains: Staphylococcus aureus S1, Escheri-
chia coli 15153, and Pesudomonas aeruginosa 9027) and
antifungal (tested strain: Candida albicans 1060) assays,
but they did not display any activity. Glyantrypine (1),
fiscalin B (4), and analogue 15 were submitted to the
National Cancer Institute’s 60-cell line in vitro antitumor
assay. The mean panel IC50 values were respectively
>100 µM, 19 µM, and 15 µM. These results imply that a
large substituent on the quinazoline ring is beneficial for
All chemicals were obtained from commercial suppliers and
used without further purification, except for CH2Cl2, which was
distilled from CaH2. TLC was carried out on precoated plates:
analytical (Merck Kieselgel 60 F254), spots visualized with UV
light and iodine vapor; preparative-scale (Aldrich, silica, 1 mm
thick). Flash column chromatography was performed with
silica (Merck EM9385, 230-400 mesh). Melting points were
taken on a Bu¨chi 535 melting point apparatus (capillary
method) and are uncorrected. 1H and 13C NMR were recorded
at 400 or 300 and at 100 or 75 MHz, respectively, in CDCl3
unless otherwise mentioned. Proton and carbon chemical shifts
are expressed in ppm relative to internal tetramethylsilane,
15N chemical shifts are calibrated with 80% MeNO2 in CDCl3
as 380.2 ppm. Protons were assigned according to COSY,
HMQC, and/or 1D-NOE experiments; coupling constant (J ) is
reported in hertz. Carbons were assigned according to DEPT
and/or HMQC experiments and multiplicity was represented
as s ) quaternary C, d ) CH, t ) CH2 and q ) CH3. For the
(23) Prepared in 90% yield by acylation of anthranilamide with
quinaldic acid chloride [prepared from the acid (1 equiv) and SOCl2)]
in the presence of Et3N (2.6 equiv) in CH2Cl2.
(24) Rauter, A. P.; Fernandes, A. C.; Figueiredo, J . A. J . Carbohydr.
Chem. 1998, 17, 1037-1045.
(25) For our successful synthesis of luotonin A by another approach,
see: Wang, H.; Ganesan, A. Tetrahedron Lett. 1998, 39, 9097-9098.

1026 J . Org. Chem., Vol. 65, No. 4, 2000
Wang and Ganesan
mass spectra data, a and b represent mass fragments in case
of a + b ) molecular weight.
(1R,4R)-4-(1H-In dol-3-ylm eth yl)-1-m eth yl-2H-pyr azin o-
[2,1-b]qu in a zolin e-3,6(1H,4H)-d ion e (3, fu m iqu in a zolin e
G). Oxazine 9 (113 mg, 0.184 mmol) was treated with CH2Cl2
(4.0 mL) and piperidine (1.0 mL) at room temperature for 12
min, followed by solvent evaporation. The vacuum-dried crude
residue was dissolved in MeCN (10 mL) and refluxed for 2 h
(after 1 h, TLC showed no amine left). The reaction mixture
was purified by preparative TLC (AcOEt: MeOH: CH2Cl2 )
50:5:45) to afford 3 (51.8 mg, 78.5%) and epimer 2 (3.1 mg,
4.7%). 3: mp 158 °C; [R]26D ) -456 (c 0.585, CHCl3) [lit.4b mp.
119-121 °C; [R]D ) -462.8 (c 0.62, CHCl3)]; IR νmax (CHCl3)
3476, 3396, 1682, 1595 cm-1; 1H NMR δ 8.39 (dd, 1H, J ) 7.8,
1.6), 8.01 (br s, 1H), 7.79 (td, 1H, J ) 7.7, 1.5), 7.57 (d, 1H, J
) 8.3), 7.54 (td, 1H, J ) 8.1, 1.0), 7.29 (dd, 1H, J ) 11.5, 7.7),
7.10 (td, 1H, J ) 7.2, 1.1), 6.87 (td, 1H, J ) 7.2, 1.1), 6.74 (d,
1H, J ) 2.4), 5.97 (br s, 1H), 5.57 (dd, 1H, J ) 5.1, 3.4), 4.46
(qd, 1H, J ) 7.0, 2.9), 3.81 (dd. 1H, J ) 15.0, 5.2), 3.74 (dd, J
) 15.0, 3.3), 0.53(d, 3H, J ) 7.0); 13C NMR δ 167.4, 161.0,
151.2, 147.2, 135.8, 134.8, 127.9, 126.9, 126.8, 123.7, 122.3,
120.1, 119.9, 118.6, 111.1, 109.4, 56.9, 27.1, 22.8; MS (EI) m/z
(relative intensity %) 358 (M+, 56), 229 (a + H, 49), 130 (b,
100); HRMS (EI) calcd for C21H18N4O2: 358.1430; found:
N-(2-Am in oben zoyl)-D-tr yp top h a n Meth yl Ester (8). To
a mixture of D-tryptophan methyl ester (1.44 g, 6.60 mmol)
and EDC (2.99 g, 15.6 mmol) in acetonitrile (70 mL) was added
anthranilic acid (1.82 g, 13.2 mmol) in 10 portions over 75 min
at room temperature with stirring. After being stirred for an
additional 100 min, the reaction mixture was concentrated
under reduced pressure. The residue was dissolved in CH2-
Cl2/aqueous Na2CO3, extracted with CH2Cl2 (×3), dried (Mg-
SO4), filtered, and concentrated. The residue was purified by
flash chromatography (eluant 1% MeOH in CH2Cl2) to yield 8
as a white solid (2.07 g, 93%): mp 136-137 °C; IR νmax (KBr)
1
1745, 1727, 1645, 1611, 1582 cm-1; H NMR δ 8.12 (br s, 1H,
D2O exchangeable), 7.57 (d, 1H, J ) 7.9), 7.36 (d, 1H, J ) 8.0),
7.21-7.15 (m, 3H), 7.10 (t, 1H, J ) 7.4), 7.02 (d, 1H, J ) 2.3),
6.65 (dd, 1H, J ) 8.5, 1.1), 6.59 (br d, 1H, J ) 8.4, D2O
exchangeable), 6.56 (t, 1H, J ) 7.5), 5.08 (dd, 1H, J ) 12.9,
5.3), 3.72 (s, 3H), 3.43 (d, 2H, J ) 5.4); 13C NMR δ (CD3OD)
174.5, 171.6, 150.2, 138.0 (s), 133.34 (d), 129.2 (d), 128.7 (s),
124.4, 122.5, 119.9, 119.2, 118.1, 117.3 (d), 117.1 (s), 112.4 (d),
110.9 (s), 55.1, 52.7, 28.2.
358.1415. Epimer 2: [R]30 ) -2.4 (c 0.15, CHCl3), its NMR
N-[(9H-Flu or en -9-ylm eth oxy)ca r bon yl]-D-a la n yl-2-a m i-
n oben zoyl-D-tr yp top h a n Meth yl Ester (6). To a solution
of compound 8 (0.368 g, 1.09 mmol) in dry CH2Cl2 (30 mL)
was added Fmoc-D-Ala-Cl12 (0.462 g, 1.34 mmol). The mixture
was stirred for 4 min, followed by addition of aqueous Na2-
CO3 (1 M, 20 mL, 20 mmol). After being stirred for a total of
1 h, the mixture was extracted with CH2Cl2 (×4), dried
(MgSO4), filtered, and concentrated. The residue was purified
by flash chromatography (eluant 0% to 10% MeOH in CH2-
Cl2) to give 6 as a white solid (0.591 g, 86%): mp 192-194 °C
D
spectra were identical to those of fumiquinazoline F.4b
(1S,4S)-4-(1H-In d ol-3-ylm eth yl)-1-m eth yl-2H-p yr a zin o-
[2,1-b]qu in a zolin e-3,6(1H,4H)-d ion e [en t-3, (+)-fu m iqu in -
a zolin e G]. ent-9 was prepared in a similar manner as that
for 9. ent-9 was treated with 20% piperidine in CH2Cl2 and
then the residue purified by preparative TLC to give ent-3
(75%) and epimer ent-2 (6%). ent-3: [R]26 ) +440 (c 0.425,
D
CHCl3) (lit.8 [R]D ) +446). Epimer ent-2: [R]30 ) +87.8 (c
D
0.115, CHCl3). The NMR spectra of ent-3 and ent-2 were
identical to those of fumiquinazoline G and F, respectively.4b
N-[(9H-F lu or en -9-ylm eth oxy)ca r bon yl]-L-va lyl-2-a m i-
n oben zoyl-D-tr yp top h a n Meth yl Ester (10). Following the
procedure given for 6, compound 8 (0.363 g, 1.08 mmol) was
reacted with Fmoc-L-Val-Cl (0.532 g, 1.46 mmol) for 2 h to yield
(dec); [R]30 ) +57.3 (c 0.49, MeOH); IR νmax (CHCl3) 3477,
D
3432, 1726, 1692, 1588 cm-1; 1H NMR δ 11.48 (br s, 1H), 8.58
(d, 1H, J ) 8.4), 8.13 (br s, 1H), 7.76 (br d, 2H, J ) 7.5), 7.66
(br d, 1H, J ) 7.1), 7.59 (br t, 1H, J ) 7.4), 7.49-7.26 (m, 8H),
7.17 (t, 1H, J ) 7.2), 7.06 (t, 1H, J ) 7.6), 7.00 (t, 1H, J )
7.7), 6.96 (br s, 1H), 6.71 (br d, 1H, J ) 7.6), 5.55 (d, 1H, J )
6.8), 5.03 (dt, 1H, J ) 7.6, 5.3), 4.44 (m, 2H), 4.36 (m, 1H),
4.26 (t, 1H, J ) 7.0), 3.73 (s, 3H), 3.40 (dd, 1H, J ) 15.3, 5.8),
3.34 (dd, 1H, J ) 15.3, 5.3), 1.53 (d, 3H, J ) 7.0); 13C NMR
(CDCl3/CD3OD, 6:1) δ 172.7, 172.2, 168.8, 156.6, 144.2, 143.8,
141.4, 138.6, 136.4, 132.8, 127.8, 127.5, 127.4, 127.2, 125.4,
125.3, 123.6, 123.4, 123.3, 122.1, 121.6, 120.9, 120.0, 119.5,
118.3, 111.7, 109.2, 67.3, 53.6, 52.7, 52.2, 47.3, 27.3, 18.4; MS
(EI) m/z (relative intensity %) 408 ([M + H - Fmoc]+, 5), 130
(100). Anal. Calcd for C37H34N4O6: C, 70.46; H, 5.43; N, 8.88.
Found: C, 70.19; H, 5.46; N, 8.84.
10 as a white solid (0.641 g, 90%): mp 197 °C (dec); [R]30
)
D
-11.8 (c 0.34, CHCl3); IR νmax (CHCl3) 1726, 1695, 1588 cm-1
;
1H NMR δ 11.02 (br s, 1H), 8.55 (br d, 2H, J ) 7.8), 7.77 (d,
2H, J ) 7.4), 7.67 (br d, 1H, J ) 7.4), 7.62 (br d, 1H, J ) 7.5),
7.55-7.27 (m, 8H), 7.15 (t, 1H, J ) 7.6), 7.05 (t, 1H, J ) 7.2),
7.01(t, 1H, J ) 7.0), 6.99 (br s, 1H), 6.68 (d, 1H, J ) 8.2), 5.54
(d, 1H, J ) 8.8), 5.09 (dt, 1H, J ) 7.3, 4.9), 4.46-4.43 (m, 2H),
4.27 (t, 1H, J ) 7.1), 4.19 (dd, 1H, J ) 8.7, 5.5), 3.74 (s, 3H),
3.46 (dd, 1H, J ) 14.9, 4.5), 3.22 (dd, 1H, J ) 14.8, 6.9), 2.20
(m, 1H), 1.02 (d, 3H, J ) 6.8,), 0.97 (d, 3H, J ) 6.9); 13C NMR
δ (CDCl3/CD3OD, 6:1) 172.4, 170.6, 168.5, 156.9, 144.1, 143.8,
141.4, 138.4, 136.4, 136.3, 132.7, 127.8, 127.5, 127.2, 125.2,
123.5, 123.2, 123.1, 122.1, 121.4, 120.8, 120.0, 119.5, 118.3,
111.5, 109.4, 67.2, 61.6, 53.3, 52.6, 47.3, 31.2, 27.8, 19.7, 17.7;
MS (EI) m/z (relative intensity %) 436 ([M + H - Fmoc]+, 0.9),
178 (100), 130 (99). Anal. Calcd for C39H38N4O6: C, 71.11; H,
5.81; N, 8.51. Found: C, 70.72; H, 5.72; N, 8.35.
N -{2-[(R )-1-N -[(9H -F lu or e n -9-ylm e t h oxy)ca r b on yl]-
a m in oeth yl]-4H-3,1-ben zoxa zin -4-ylid en e}-D-tr yp top h a n
Meth yl Ester (9). To a solution of compound 6 (0.179 g, 0.284
mmol) in CH2Cl2 (15 mL) were added Ph3P (0.370 g, 1.41
mmol), I2 (0.352 g, 1.39 mmol), and N,N-diisopropylethylamine
(0.50 mL, 2.87 mmol). The reaction mixture was stirred at
room temperature for 2.5 h, quenched with aqueous Na2CO3,
and extracted with CH2Cl2 (×3), dried (MgSO4), filtered, and
concentrated. The residue was purified by flash chromatog-
raphy (40-50% AcOEt/hexanes with 2% Et3N) to give 9 as a
N-{2-[(S)-1-N-[(9H-F lu or en -9-ylm eth oxy)ca r bon yl]a m i-
n o-2-m eth ylp r op yl]-4H-3,1-ben zoxa zin -4-ylid en e}-D-tr yp -
t op h a n Met h yl E st er (11). To a solution of compound 10
(0.362 g, 0.550 mmol) in CH2Cl2 (20 mL) were added Ph3P
(0.715 g, 2.73 mmol), I2 (0.677 g, 2.67 mmol), and N,N-
diisopropylethylamine (1.00 mL, 5.74 mmol). The reaction
mixture was stirred at room temperature for 8.2 h and
quenched with aqueous Na2CO3, extracted with CH2Cl2 (×3),
dried (MgSO4), filtered, and concentrated. The residue was
purified by flash chromatography (eluant 30% to 50% AcOEt/
hexanes with 2% Et3N) to give 11 as a white solid (0.290 g,
82%) which was crystallized from CH2Cl2/hexanes to yield
white solid (0.113 g, 65%): mp 199-200 °C; [R]30 ) +121 (c
D
0.22, CHCl3); IR νmax (KBr) 1719, 1692, 1642 cm-1; 1H NMR δ
8.20 (d, 1H, J ) 7.6), 7.76 (br d, 3H, J ) 7.4), 7.67 (br d, 1H,
J ) 7.7), 7.61 (br t, 2H, J ) 7.3), 7.54 (td, 1H, J ) 7.7, 1.5),
7.40-7.26 (m, 6H), 7.18 (br d, 1H, J ) 7.8), 7.09 (t, 1H, J )
7.6), 7.03 (t, 1H, J ) 7.6), 6.99 (br s, 1H), 5.31 (d, 1H, J ) 6.8),
4.88 (dd, 1H, J ) 8.4, 5.0), 4.50-4.35 (m, 3H), 4.22 (t, 1H, J )
6.5), 3.71 (s, 3H), 3.47 (dd, 1H, J ) 14.2, 4.8), 3.25 (dd, 1H, J
) 14.3, 8.5), 1.13 (d, 3H, J ) 6.7); 13C NMR (DMSO-d6) δ (at
least two rotamers) 174.0, 171.9, 165.9, 160.2, 155.7, 147.1,
143.7, 142.6, 141.1, 139.4, 137.4, 136.1, 136.0, 133.7, 133.1,
131.0, 129.9, 128.8, 128.3, 127.6,127.4, 127.3, 127.0, 126.0,
125.6, 125.2, 125.1, 123.7, 123.6, 121.3, 120.9, 120.8, 120.1,
120.0, 118.7, 118.5, 118.4, 118.2, 118.0, 111.4. 110.3, 110.0,
65.7, 59.3, 52.3, 51.7, 49.0, 46.6, 29.0, 26.7, 17.3. Anal. Calcd
for C37H32N4O5: C, 72.53; H, 5.26; N, 9.14. Found: C, 72.30;
H, 5.16; N, 9.01.
colorless needles: mp 129 °C (dec); [R]30 ) +78.0 (c 0.64,
D
MeOH); IR νmax (CHCl3) 1725, 1681, 1649, 1608 cm-1; 1H NMR
δ 8.18 (d, 1H, J ) 7.7), 8.09 (br s, 1H), 7.77 (br d, 2H, J ) 7.3),
7.70-7.60 (m, 3H), 7.53(t, 1H, J ) 7.5), 7.45-7.20 (m, 7H),
7.11(t, 1H, J ) 7.1), 7.07 (br s, 1H), 7.02 (t, 1H, J ) 7.2), 5.40
(d, 1H, J ) 9.2), 4.85 (dd, 1H, J ) 8.2, 4.7), 4.45 (br d, 2H, J
) 7.0), 4.26 (t, 1H, J ) 6.8), 4.02 (dd, 1H, J ) 9.0, 5.2), 3.69 (s,
3H), 3.48 (dd, 1H, J ) 14.3, 4.7), 3.26 (dd, 1H, J ) 14.2, 8.6),
1.95 (m, 1H), 0.87 (d, 3H, J ) 6.6), 0.79 (d, 3H, J ) 6.7); 13C

Total Synthesis of the Fumiquinazoline Alkaloids
J . Org. Chem., Vol. 65, No. 4, 2000 1027
NMR δ 172.9, 158.3, 156.3, 147.7, 143.9, 143.8, 141.3, 141.0,
136.1, 133.3, 128.2, 127.7, 127.5, 127.1, 126.2, 125.1, 122.8,
122.0, 120.0, 119.2, 118.8, 112.3, 111.3, 66.9, 60.2, 57.9, 52.2,
7.03 (t, 1H, J ) 7.5), 6.92 (t, 1H, J ) 7.4), 4.66 (m, 1H, Trp-
CHN), 4.30 (m, 2H, CH2O), 4.24 (m, 1H), 3.73 (m, 2H, Gly-
CH2N), 3.54 (s, 3H, OCH3), 3.24 (d, 2H, J ) 8.1); 13C NMR
(DMSO-d6) δ 171.9, 168.4, 168.1, 156.6, 143.8, 143.7, 140.6,
138.6, 136.0 (s), 132.2, 128.3, 127.5, 126.9, 125.1, 123.5, 122.5,
120.9, 120.0, 119.9 (d), 119.6 (s), 118.3, 117.9, 111.4 (d), 109.7
(s), 109.6 (s), 65.8 (t), 53.4 (Trp-CHN), 51.8 (q), 46.6 (d), 45.1
(Gly-CH2N), 26.2 (t). Anal. Calcd for C36H32N4O6‚1/4H2O: C,
69.61; H, 5.27; N, 9.02. Found: C, 69.52; H, 5.61; N, 8.71.
N-[(9H-F lu or en -9-ylm eth oxy)ca r bon yl]-L-a la n yl-2-a m i-
n oben zoyl-D-tr yp top h a n Meth yl Ester (13b). Following the
procedure given for 6, 8 (0.331 g, 0.98 mmol) was reacted with
Fmoc-L-Ala-Cl12 (0.496 g, 1.44 mmol) for 4.7 h to give 14b as
1
47.3, 31.4, 29.6, 19.1, 17.3; H-15N HMBC: three nitrogens
were identified at δ 82.0 (Fmoc-NH), 225.0 and 224.7 (Trp-
Nd; MS (EI) m/z (relative intensity %) 640 (M+, 0.6), 511 (a +
H, 2), 130 (b, 96). Anal. Calcd for C39H38N4O6‚H2O: C, 71.11;
H, 5.81; N, 8.51. Found: C, 70.81; H, 5.48; N, 8.31.
(1S,4R)-4-(1H-In d ol-3-ylm eth yl)-1-isop r op yl-2H-p yr a zi-
n o[2,1-b]qu in azolin e-3,6(1H,4H)-dion e (4, fiscalin B). Com-
pound 11 (115 mg, 0.179 mmol) was dissolved in CH2Cl2 (3.2
mL), followed by addition of piperidine (0.8 mL), and stirred
at room temperature for 12 min. The resulting solution was
concentrated under reduced pressure to provide a white
residue which was triturated with hexanes (×1), CH2Cl2/PhMe
(×1), and hexanes (×1). The residue was dissolved in aceto-
nitrile (10 mL) and refluxed for 18.7 h in the presence of DMAP
(28 mg, 0.23 mmol). The reaction mixture was concentrated
and purified by preparative TLC (MeOH/CH2Cl2/EtOAc ) 2.5:
47.5:50) to yield 4 as pale yellow crystals (50 mg, 72%): mp
176.5-178.5 °C; [R]30 ) -609 (c 0.59, CHCl3), [R]26 ) -504
a white solid (0.416 g, 67%): mp 144-146 °C; [R]30 ) -28.1
D
(c 0.26, CHCl3); IR νmax (CHCl3) 1725, 1692, 1650, 1602, 1588
cm-1; 1H NMR δ 11.22 (br s, 1H, anilide NH), 8.55 (d, 1H, J )
8.2), 8.40 (br s, 1H, indole-NH), 7.77 (br d, 2H, J ) 7.2), 7.70
(d, 1H, J ) 7.3), 7.63 (d, 1H, J ) 7.3), 7.52-7.26 (m, 8H), 7.16
(t, 1H, J ) 7.5), 7.05 (t, 1H, J ) 7.7), 7.01 (t, 1H, J ) 7.2),
6.98 (br s, 1H), 6.70 (d, 1H, J ) 7.8)), 5.50 (d, 1H, J ) 6.8,
Fmoc-NH), 5.04 (m, 1H), 4.48-4.35 (m, 3H), 4.26 (t, 1H, J )
7.0), 3.72(s, 3H), 3.44 (dd, 1H, J ) 14.8, 4.7), 3.25 (dd, 1H, J
) 14.7, 6.1), 1.49 (d, 3H, J ) 7.0); 13CNMR (CDCl3-CD3OD,
v/v ) 3/1) δ 172.7, 172.4, 168.9, 156.9, 144.4, 144.0, 141.5,
138.6, 136.7 (s), 132.8, 127.9 (d), 127.6 (s),127.6, 127.3, 125.6,
125.4, 123.7, 123.5, 122.0, 121.6, 120.1, 119.4, 118.4, 111.8 (d),
109.4 (s), 67.4(t), 53.7, 52.6, 52.3, 47.5, 27.7 (t), 18.2 (q). Anal.
Calcd for C37H34N4O6: C, 70.46; H, 5.43; N, 8.88. Found: C,
70.14; H, 5.74; N, 8.67.
D
D
(c 0.64, MeOH) [lit.5b mp 164.5-170.5 °C; [R]21.5 ) -124 (c
D
0.021, MeOH)]; IR νmax (CHCl3) 3475, 3401, 1682, 1596 cm-1
;
1H NMR δ 8.38 (d, 1H, J ) 8.0), 8.01 (br s, 1H), 7.77 (ddd, 1H,
J ) 8.3, 7.0, 1.4), 7.56 (d, 1H, J ) 8.2), 7.53 (t, 1H, J ) 7.9),
7.45 (d, 1H, J ) 8.1), 7.29 (d, 1H, J ) 8.2), 7.13 (t, 1H, J )
7.8), 6.94 (t, 1H, J ) 7.8), 6.60 (d, 1H, J ) 2.2), 5.67 (dd, 1H,
J ) 4.8, 2.5), 5.57 (br s, 1H), 3.74 (dd, 1H, J ) 15.0, 2.8), 3.65
(dd, 1H, J ) 15.0, 5.3), 2.69 (d, 1H, J ) 2.3), 2.63 (m, 1H),
0.65 (d, 3H, J ) 6.6), 0.63 (d, 3H, J ) 7.0); 13C NMR δ 169.5,
160.9, 150.3,147.1, 136.1, 134.7, 127.3, 127.2, 127.0, 126.9,
123.6, 122.6, 120.2, 120.0, 118.7, 111.1, 109.4, 58.2, 56.8, 29.5,
27.4, 18.8, 14.8; 1H-15N HSQC and HMBC: four nitrogens
were identified at δ 110.5 (Val-NH), 124.5 (indole NH), 165.9
(Trp-N) and 232.6 (Ar-Nd); MS (EI) m/z (relative intensity
%) 386 (M+, 56), 257 (a + H, 31), 130 (b, 100); HRMS (EI)
calcd for C23H22N4O2: 386.1743; found: 386.1731.
N-[(9H-F lu or en -9-ylm eth oxy)ca r bon yl]-L-p h en a la n yl-
2-a m in oben zoyl-D-tr yp top h a n Meth yl Ester (13c). Fol-
lowing the procedure given for 6, 8 (0.322 g, 0.96 mmol) was
reacted with Fmoc-L-Phe-Cl (0.508 g, 1.24 mmol) for 2 h to
give 13c as a white solid (0.652 g, 97%): [R]30 ) -47.7 (c
D
0.375, CHCl3); IR νmax (KBr) 3422, 3317, 1741, 1702, 1686, 1656
cm-1; 1H NMR δ 11.24 (br s, 1H, anilide NH), 8.54 (d, 1H, J )
8.3), 8.36 (br s, 1H, indole NH), 7.76 (br d, 2H, J ) 7.5), 7.60
(d, 1H, J ) 7.5), 7.55 (d, 1H, J ) 7.5), 7.49 (d, 1H, J ) 8.2),
7.45 (t, 1H, J ) 8.0), 7.39 (br t, 2H, J ) 7.1), 7.32-7.25 (m,
6H), 7.22-7.14 (m, 4H), 7.06 (ddd, 1H, J ) 8.0, 7.1, 0.9), 7.00
(td, 1H, J ) 7.7, 1.1), 6.95 (br s, 1H, indole C2-H), 6.67 (d, 1H,
J ) 7.8, Trp-CHNH), 5.45 (d, 1H, J ) 7.8, Fmoc-NH-Phe),
5.00 (m, 1H, Trp-CHN), 4.60 (m, 1H, Phe-CHN), 4.38 (d, 2H,
J ) 7.0, CH2O), 4.23 (t, 1H, J ) 7.2), 3.70 (s, 3H, OCH3), 3.40
(dd, 1H, J ) 14.8, 4.8, Trp-CH2), 3.25-3.22 (m, 2H), 3.12 (dd,
1H, J ) 13.9, 7.0); 13C NMR δ 172.0, 169.7, 168.0, 156.0, 144.0,
143.7, 141.3, 141.3, 138.8, 136.1, 136.1 (s), 132.8, 129.4, 128.7,
127.7 (d), 127.5 (s), 127.1, 127.0, 126.7, 123.3, 122.8, 122.3,
121.4 (d), 120.3 (s), 120.0, 119.9, 119.7, 118.4, 111.4 (d), 67.3
(CH2O), 57.1 (Phe-CHN), 53.2 (Trp-CHN), 52.6 (q), 38.7 (Phe-
CH2), 27.9 (Trp-CH2). Anal. Calcd for C43H38N4O6: C, 73.07;
H, 5.42; N, 7.93. Found: C, 72.89; H, 5.79; N, 7.73.
(S)-2-[(2-Am in o-1-m eth oxy-3-m eth ylbu tylid en e)a m in o]-
ben zoyl-D-tr yp top h a n Meth yl Ester (12). Oxazine 11 (104
mg, 0.163 mmol) was treated with CH2Cl2 (3.2 mL) and
piperidine (0.8 mL) at room temperature for 12 min and then
evaporated to dryness. The vacuum-dried crude residue was
dissolved in MeOH (10 mL) and DMAP (26.6 mg, 0.218 mmol)
and heated at reflux for 60 h. The reaction mixture was
purified by preparative TLC (AcOEt:MeOH:CH2Cl2 ) 42:3:55)
to give 4 (26 mg, 42%) and a major byproduct 12 (17 mg, 23%).
12: 1H NMR δ 8.74 (d, 1H, J ) 8.4, CONH), 8.20 (br s, 1H,
indole NH), 8.15 (dd, 1H, J ) 7.8, 1.3), 7.49 (d, 1H, J ) 8.1),
7.37 (t, 1H, J ) 7.4), 7.29 (d, 1H, J ) 8.2), 7.17 (t, 1H, J )
7.7), 7.13 (t, 1H, J ) 8.2), 7.02 (t, 1H, J ) 7.5), 6.99 (br s, 1H),
6.70 (d, 1H, J ) 7.9), 5.28 (dt, 1H, J ) 8.7, 5.1), 3.63 (s, 3H,
CO2CH3), 3.41 (dd, 1H, J ) 14.7, 4.9, Trp-CH2), 3.33 (s, 3H,
OCH3), 3.32 (dd, 1H, J ) 14.7, 5.7, Trp-CH2), 3.13 (d, 1H, J )
8.4, Val-CHN), 1.66 (m, 1H, Val-CH), 0.79 (s, 3H, Me), 0.67
(s, 3H, Me); 13C NMR δ 172.5 (CO2Me), 166.2 (-NdCO), 165.9
(CONH), 131.9 (d), 131.1 (d), 127.6 (s), 125.3 (s), 123.6, 123.1,
122.3, 122.0 119.5, 118.8, 111.0 (d), 110.2 (s), 56.2 (Val-CHN),
53.2 (CO2CH3), 53.1 (Trp-CHN), 52.1 (OMe), 32.7 (Val-CH),
28.5 (Trp-CH2), 19.1 (q), 18.4 (q). 12 may be present as
rotamers; at least two species were seen by NMR. 1D NOE
for major isomer: δ 6.70 f 3.33 (OMe). 1H-15N HMBC: proton
at δ 6.70 has correlation with nitrogen at δ 238 (-NdCOMe);
MS (ESI, positive mode) m/z 451.3 ([M + H]+).
N-{2-[N-[(9H -F lu or en -9-ylm et h oxy)ca r b on yl]a m in o-
m eth yl]-4H-3,1-ben zoxazin -4-yliden e}-D-tr yptoph an Meth -
yl Ester (14a ). Following the procedure given for 9, 13a (0.498
g, 0.807 mmol) was dehydrated at room temperature for 7 h.
The residue was purified by flash chromatography (50% to 60%
AcOEt/hexanes) to give 14a as an off-white solid (0.435 g, 90%)
and recovered 13a (0.036 g, 7%). 14a : mp 104 °C (dec); [R]30
D
) +141 (c 0.33, CHCl3); IR νmax (KBr) 3398, 3326, 1720, 1689,
1
1535 cm-1; H NMR δ 8.17 (d, 1H, J ) 7.9), 7.94 (br s, 1H),
7.78 (d, 1H, J ) 7.3), 7.64 (br t, 2H overlapped), 7.51 (t, 1H, J
) 7.0), 7.44-7.23 (m, 9H), 7.13 (td, 1H, J ) 6.7, 1.2), 7.05 (t,
1H, J ) 6.3), 6.94 (d, 1H, J ) 1.8), 5.03 (br t like, 1H), 4.91
(dd, 1H, J ) 9.2, 4.3), 4.30 (d, 2H, J ) 6.3), 4.24 (t, 1H, J )
6.4), 3.74 (s, 3H), 3.64 (dd, 1H, J ) 18.3, 5.5), 3.48 (dd, 1H,
partially overlapped, J ) [12.2], 4.3), 3.42 (dd, 1H, partially
overlapped, J ) [17.7], 5.5), 3.17 (dd, 1H, J ) 14.0, 9.8); 13C
NMR δ 172.9, 156.2, 156.0, 147.3, 143.8, 141.3, 140.9, 136.0
(s), 133.3, 128.1, 127.7 (d), 127.5 (s), 127.1, 126.3, 125.8, 125.0,
123.3, 121.9, 120.0, 119.3 (d), 119.1 (s), 118.8 (d), 111.9 (s),
111.2, 66.9 (CH2O), 59.5 (CHN), 52.2 (OCH3), 47.1 (d), 41.7
(CH2N), 29.5 (t).
N-[(9H -F lu or en -9-ylm et h oxy)ca r b on yl]-glycyl-2-a m i-
n oben zoyl-D-tr yp top h a n Meth yl Ester (13a ). Following the
procedure given for 6, compound 8 (0.330 g, 0.979 mmol) was
reacted with Fmoc-Gly-Cl (0.406 g, 1.281 mmol) for 2 h to give
13a as a white solid (0.594 g, 98%): mp 183-185 °C; [R]30
)
D
-17.3 (c 0.23, CHCl3); IR νmax (KBr) 3326, 1739, 1696, 1682,
1632 cm-1; 1H NMR (DMSO-d6) δ 11.59 (br s, 1H), 10.83 (br s,
1H), 9.04 (d, 1H, J ) 7.5, Trp-CHNH), 8.48 (d, 1H, J ) 8.4),
7.97 (t, 1H, J ) 5.9, Fmoc-NH-Gly), 7.90 (d, 2H, J ) 7.5), 7.77
(d, 1H, J ) 7.7), 7.70 (d, 1H, J ) 7.3), 7.69 (d, 1H, J ) 7.4),
7.51 (t, 1H, J ) 7.6), 7.48 (d, 1H, J ) 7.7), 7.41 (t, 2H, J )
7.5), 7.32-7.26 (m, 3H), 7.15 (br s, 1H), 7.15 (t, 1H, J ) 7.5),
N -{2-[(S )-1-N -[(9H -F lu or e n -9-ylm e t h oxy)ca r b on yl]-
a m in oeth yl]-4H-3,1-ben zoxa zin -4-ylid en e}-D-tr yp top h a n

1028 J . Org. Chem., Vol. 65, No. 4, 2000
Wang and Ganesan
Meth yl Ester (14b). Following the procedure given for 9, 13b
(0.269 g, 0.425 mmol) was dehydrated for 5.5 h and the
reaction mixture purified by flash chromatography (eluant 30-
60% AcOEt/hexanes, no Et3N added) to give 14b as a white
solid (0.186 g, 71%) and recovered 13b (0.024 g, 9%). 14b:
mp124-126 °C; [r]30D ) +92.0 (c 0.65, MeOH); IR νmax (CHCl3)
15.3, 3.8), 3.66 (dd, J ) 15.3, 5.6), 3.11 (q, 1H, J ) 6.6), 1.36
(d, 3H, J ) 6.6); 13C NMR δ 169.3, 160.8, 151.7, 147.1, 136.0
(s), 134.7, 127.3, 127.1, 126.8 (d), 123.6 (s), 122.5, 120.2 (s),
120.0, 118.5, 111.2 (d), 109.4 (s), 57.5, 49.2 (d), 27.1 (t), 19.1
(q); MS (EI) m/z (relative intensity %) 358 (M+, 78), 229 (a
+H, 58), 130 (b,100); HRMS (EI) calcd. for
C21H18N4O2:
1
1725, 1680, 1511 cm-1; H NMR δ 8.18 (d, 1H, J ) 7.8), 8.00
358.1430; found: 358.1473.
(br s, 1H, indole-NH), 7.78 (br d, 2H, J ) 7.2), 7.64 (br t, 3H,
J ) 8.7), 7.53 (td, 1H, J ) 7.6, 1.3), 7.43-7.24 (m, 7H), 7.12
(t, 1H, J ) 7.4), 7.02 (t, 1H, J ) 7.8), 7.02 (br s, 1H), 5.32 (d,
1H, J ) 7.7, Fmoc-NH), 4.86 (dd, 1H, J ) 8.5, 4.5), 4.45 (br d,
2H, J ) 7.0), 4.25 (t, 1H, J ) 6.6), 4.11 (t, 1H, J ) 7.0), 3.71
(s, 3H, OMe), 3.48 (dd, 1H, J ) 14.2, 4.6), 3.24 (dd, 1H, J )
14.2, 8.9), 1.23 (d, 3H, J ) 6.9); 13C NMR δ 172.9, 159.2, 155.5,
147.6, 144.0, 143.8, 141.3, 141.0, 136.0 (s), 133.3, 128.2, 127.7
(d), 127.5 (s), 127.1, 126.4, 126.0, 125.1, 123.0, 122.0, 120.0,
119.3 (d), 119.1 (s), 118.8 (d), 112.2 (s), 111.2 (d), 66.8 (t), 59.8
(d), 52.2 (d), 48.6 (d), 47.2 (d), 29.6 (t), 19.2. Anal. Calcd for
C37H32N4O5‚5/4H2O: C, 69.96; H, 5.47; N, 8.82. Found: C,
69.88; H, 5.48; N, 8.73.
(1S,4R)-4-(1H-In d ol-3-ylm eth yl)-1-(p h en ylm eth yl)-2H-
p yr a zin o[2,1-b]qu in a zolin e-3,6(1H,4H)-d ion e (15). Fol-
lowing the procedure given for 3, oxazine 14c (286 mg, 0.415
mmol) was deprotected and then refluxed in MeCN for 3 h.
Purification by preparative TLC (50% AcOEt/hexanes) gave
product 15 (140 mg, 78%) and cis-epimer (9 mg, 5%). Com-
pound 15: [R]30D ) -623 (c 0.27, CHCl3); IR νmax (CHCl3) 3310,
1
1678, 1598 cm-1; H NMR δ 8.39 (dd, 1H, J ) 8.4, 1.6), 8.11
(br s, 1H, indole NH), 7.78 (td, 1H, J ) 6.9, 1.2), 7.63 (d, 1H,
J ) 8.0), 7.56 (td, 1H, J ) 8.1, 1.1), 7.43 (d, 1H, J ) 8.0), 7.40
(d, 1H, J ) 8.2), 7.24 (td, 1H, J ) 8.1, 1.0), 7.19-7.16 (m, 3H),
6.93 (td, 1H, J ) 7.2, 0.8), 6.62 (d, 1H, J ) 2.1, indole C2-H),
6.50 (br d, 1H, J ) 7.1, 2H, Ph), 5.65 (dd, 1H, J ) 5.3, 2.7,
Trp-CHN), 5.35 (br s, 1H, amide NH), 3.75 (dd, 1H, J ) 15.0,
2.6, Phe-CH2), 3.65 (dd, 1H, J ) 15.0, 5.4, Phe-CH2), 3.62 (dd,
1H, J ) 14.8, 3.4, Trp-CH2), 2.97 (dd, 1H, J ) 11.2, 3.6, Trp-
CHN), 2.52 (dd, 1H, J ) 14.7, 11.2, Trp-CH2); 13C NMR δ 169.2,
160.7, 151.0, 146.9, 136.1, 134.9 (s), 134.8, 129.1 (d), 128.4 (d),
127.3, 127.2 (d), 127.1 (s), 126.9, 123.8, 122.8, 120.6 (d), 120.3
(s), 119.0, 111.1 (d), 109.6 (s), 57.4 (Phe-CHN), 52.8 (Trp-CHN),
37.9 (Phe-CH2), 27.2 (Trp-CH2); MS (EI) m/z (relative intensity
%) 434 (M+, 52), 305 (a + H, 40), 130 (b, 100). Anal. Calcd for
N-{2-[(S)-1-N-[(9H-F lu or en -9-ylm eth oxy)ca r bon yl]a m i-
n o2-p h en ylet h yl]-4H -3,1-b en zoxa zin -4-ylid en e}-D-t r yp -
top h a n Meth yl Ester (14c). Following the procedure given
for 9, 13c (0.509 g, 0.720 mmol) was dehydrated for 7 h to
give 14c as an off-white solid (0.430 g, 87%) and recovered
16a (0.016 g, 3%). 14c: [R]30D ) +38.8 (c 0.34, CHCl3); IR νmax
1
(KBr) 3383, 3334, 1725, 1682, 1508 cm-1; H NMR δ (major
rotamer) 8.18 (dd, 1H, J ) 7.9, 1.2), 8.04 (br s, 1H, indole NH),
7.78 (br d, 2H, J ) 7.5), 7.66 (br d, 2H, J ) 10.5), 7.61-7.58
(m, 2H), 7.50 (td, 1H, J ) 7.7, 1.4), 7.43-7.14 (m, 11H), 7.08
(t, 1H, J ) 7.4), 7.03 (br s, 1H), 6.95 (d, 2H, J ) 6.0), 5.35 (d,
1H, J ) 8.2, Fmoc-NH-Phe), 4.71 (dd, 1H, J ) 8.6, 4.6), 4.48
(dd, 1H, J ) 10.6, 7.2, CH2O), 4.38 (dd, 1H, J ) 10.6, 6.8,
CH2O), 4.29 (dt, 1H, J ) 8.0, 5.9, Phe-CHN), 4.24 (t, 1H, J )
6.7, Fmoc-CH), 3.71 (s, 3H, OCH3), 3.47 (dd, 1H, J ) 14.2, 4.5,
Trp-CH2), 3.22 (dd, 1H, J ) 14.2, 8.7, Trp-CH2), 2.99 (dd, 1H,
J ) 13.8, 5.8, Phe-CH2), 2.88 (dd, 1H, J ) 13.7, 5.9, Phe-CH2);
there was about 20% of minor rotamer, with broad peaks: 6.80
(0.35H), 4.99 (br d, 0.21 H), 4.55 (0.47H), 2.62 (0.35H); 13C
NMR δ 172.9, 157.6, 155.4, 147.4, 143.7, 141.3, 140.7, 136.1,
135.5 (s), 133.3, 129.3, 128.5, 128.3, 127.7 (d), 127.5 (s), 127.0,
126.9, 126.4, 126.1, 125.1, 123.0, 122.0, 120.0, 119.3 (d), 119.0
(s), 118.8 (d), 112.0 (s), 111.3 (d), 66.8 (CH2O), 59.9 (d), 53.5
(d), 52.2 (q), 47.2 (d), 38.63 (t), 29.54 (t).
C
27H22N4O2‚1/3H2O: C, 73.62; H, 5.19; N, 12.72. Found: C,
73.69; H, 5.58; N, 12.37. Cis epimer of 15: [R]30 ) -246 (c
D
0.315, CHCl3); IR νmax (KBr) 3475, 3386, 1681, 1593 cm-1; 1H
NMR δ 8.42 (dd, 1H, J ) 8.0, 1.0), 8.11 (br s, 1H, indole NH),
7.83 (ddd, 1H, J ) 8.3, 7.1, 1.4), 7.67 (d, 1H, J ) 8.0), 7.59-
7.55 (m, 2H), 7.30 (d, 1H, J ) 8.1), 7.21 (td, 1H, J ) 7.6, 0.9),
7.14 (dd, 2H, J ) 5.6, 3.7), 7.10 (t, 1H, J ) 8.0), 6.62 (d, 1H, J
) 2.4, indole C2-H), 6.35-6.32 (m, 2H), 5.56 (t, 1H, J ) 4.3),
5.55 (br s, 1H, amide NH), 4.38 (dt, 1H, J ) 11.7, 2.8), 3.84
(dd, 1H, J ) 15.1, 3.2), 3.82 (dd, 1H, J ) 15.2, 4.4), 3.01 (dd,
1H, J ) 13.1, 3.0), 0.59 (dd, 1H, J ) 12.9, 11.9); 13C NMR δ
166.5, 160.9, 150.1, 147.2, 135.8, 135.6 (s), 134.9, 129.2, 128.9
(d), 128.1 (s), 127.2, 127.1, 127.0, 126.9, 123.5, 122.8, 120.5
(d), 120.2 (s), 119.5, 111.4 (d), 109.7 (s), 57.8 (d), 56.8 (d), 42.8
(t), 26.6 (t); MS (ESI, positive mode) m/z 435.2 ([M + H]+).
N-[2-(Acetyla m in o)ben zoyl]-L-tr yp top h a n Meth yl Es-
ter (16a ). To a solution of ent-8 (133 mg, 0.393 mmol), CH2-
Cl2 (5 mL) and Et3N (0.16 mL, 1.15 mmol) was added Ac2O
(0.074 mL, 0.78 mmol) via a syringe. After 23 h, the mixture
was diluted with aqueous Na2CO3 and extracted with CH2Cl2
(×3). After workup, the residue was purified by flash chro-
matography (5% MeOH/CH2Cl2) and gave the acetamide as a
syrup (147 mg, 99%): IR νmax (CHCl3) 1741, 1687, 1644, 1601,
(R)-4-(1H-in dol-3-ylm eth yl)-2H-pyr azin o[2,1-b]qu in azo-
lin e-3,6(1H,4H)-d ion e (1, glya n tr yp in e). Following the
procedure given for 3, 14a (0.264 g, 0.441 mmol) was depro-
tected and then refluxed in MeCN for 2 h; after chromatog-
raphy, 1 was obtained as white crystals (0.132 g, 87%): mp
159-161 °C (foam); [R]30D ) -522 (c 0.24, CHCl3); IR νmax (KBr)
3265, 1681, 1600, 1474 cm-1; 1H NMR (DMSO-d6) δ 10.95 (br
s, 1H), 8.35 (d, 1H, J ) 4.3, CONH), 8.22 (d, 1H, J ) 7.6), 7.83
(td, 1H, J ) 8.0, 1.5), 7.56 (t, 1H, J ) 7.4), 7.55 (d, 1H, J )
7.8), 7.33 (d, 1H, J ) 8.1), 7.28 (d, 1H, J ) 7.9), 7.02 (t, 1H, J
) 7.2), 6.88 (d, 1H, J ) 2.3), 6.79 (t, 1H, J ) 7.5), 5.29 (t, 1H,
J ) 4.8), 3.82 (dd, 1H, J ) 17.0, 4.5, Gly-CH2), 3.45 (m, strongly
coupled AB system, 2H, Trp-CH2), 3.07 (d, 1H, J ) 17.0, Gly-
CH2); 13C NMR (DMSO-d6) δ 167.6, 159.9, 149.2, 146.9, 135.9
(s), 134.6 (d), 127.1 (s), 126.6, 126.5, 126.2, 124.3, 121.2 (d),
119.8 (s), 118.6, 117.7, 111.4 (d), 107.7 (s), 56.4 (d), 43.7 (t),
26.5 (t). MS (EI) m/z (relative intensity %) 344 (M+, 52), 215
(a + H, 20), 130 (b, 100).
1
1587 cm-1; H NMR δ 10.92 (br s, 1H), 7.52 (d, 1H, J ) 7.8),
7.39 (t, 1H, J ) 7.8), 7.33 (d, 1H, J ) 8.1), 7.25 (d, 1H, J )
7.4), 7.17 (t, 1H, J ) 7.5), 7.08 (t, 1H, J ) 7.4), 6.96 (br s, 1H,
indole C2-H), 6.92 (t, 1H, J ) 7.5), 6.81 (d, 1H, J ) 7.1, NH),
5.05 (dd like, 1H, J ) 12.3, 5.4), 3.74 (s, 3H), 3.45 (dd, 1H, J
) 15.0, 5.3), 3.41 (dd, 1H, J ) 14.9, 5.6), 2.14 (s, 3H); 13C NMR
δ 172.1, 169.2, 168.5, 139.5, 136.2, 132.8, 127.5 (s), 126.9 (d),
122.9, 122.8, 122.4, 121.4, 119.8 (d), 119.65 (s), 118.4, 111.5
(d), 109.5 (s), 53.5 (d), 52.6 (q), 27.5 (t), 25.3 (q).
N-[2-(Ben zoyla m in o)ben zoyl]-L-tr yp top h a n Meth yl Es-
ter (16b). To a solution of ent-8 (0.122 g, 0.361 mmol), CH2-
Cl2 (5 mL) and Et3N (0.12 mL, 0.86 mmol) was added PhCOCl
(0.063 mL, 0.54 mmol) via a syringe. The mixture was stirred
at room temperature for 2 h and then diluted with aqueous
Na2CO3 and extracted with CH2Cl2 (×3). After workup, the
residue was treated with CH2Cl2/hexanes to give 16b quan-
titatively as a solid: 1H NMR δ 12.03 (br s, 1H), 8.81(d, 1H, J
) 8.0), 8.12 (br s, 1H), 8.03 (dd, 1H, J ) 7.9, 1.56), 7.55-7.48
(m, 5H), 7.33 (td, 2H, J ) 7.1, 1.2), 7.19 (t, 1H, J ) 7.1), 7.08
(t, 1H, J ) 7.5), 7.05-7.00 (m, 2H), 6.80 (br s, 1H, J ) 7.6),
5.15 (dt, 1H, J ) 5.2, 2.4), 3.75 (s, 3H), 3.49 (dd, 1H, J ) 15.0,
5.8), 3.44 (dd, 1H, J ) 15.0, 5.5); 13C NMR (CDCl3/CD3-
COCD3,) 3:1) δ 172.2, 169.2, 165.4, 140.3, 136.7, 135.1, 132.9,
(1S,4R)-4-(1H-In d ol-3-ylm eth yl)-1-m eth yl-2H-p yr a zin o-
[2,1-b]qu in a zolin e-3,6(1H,4H)-d ion e (2, fu m iqu in a zolin e
F ). Following the procedure given for 3, oxazine 14b (96.6 mg,
0.158 mmol) was deprotected and then refluxed in MeCN for
2 h. Purification by preparative TLC (AcOEt:MeOH:CH2Cl2
) 50:5:45) gave 2 (46.8 mg, 82.8%) and epimer 3 (2.0 mg, 3.5%).
Epimer 3: [R]30 ) -7.0 (c 0.10, CHCl3). Synthetic 2: mp 137
D
°C (foam), [R]30 ) -516 (c 0.74, CHCl3){lit:4b mp. 88-90 °C,
D
[R]D ) -411 (c 1.36, CHCl3)]}; 1H NMR δ 8.37 (d, 1H, J ) 8.0),
8.19 (br s, 1H, indole-NH), 7.77 (td, 1H, J ) 7.6, 1.2), 7.59 (d,
1H, J ) 8.1), 7.53 (t, 1H, J ) 7.5), 7.40 (d, 1H, J ) 8.0), 7.30
(d, 1H, J ) 8.2), 6.92 (t, 1H, J ) 7.6), 6.71(d, 1H, J ) 2.3),
6.35 (br s, 1H, NH), 5.68 (t, 1H, J ) 4.3), 3.70 (dd, 1H, J )

Total Synthesis of the Fumiquinazoline Alkaloids
J . Org. Chem., Vol. 65, No. 4, 2000 1029
132.0, 128.9, 127.7, 127.6, 127.5, 123.5, 122.8, 122.0, 120.0,
118.5, 111.7, 109.7, 53.8, 52.5, 27.6.
quantitatively. Shorter reaction times resulted in incomplete
reaction: 2 h gave 17c (58%) and recovered 16c (39%); 6.2 h
N -[2-(2-Me t h ylp r op a n oyla m in o)b e n zoyl]-L-t r yp t o-
p h a n Meth yl Ester (16c). Following the procedure given for
16b, ent-8 was acylated with Me2CHCH2COCl to give 16c
gave 17c (88%) and recovered 16c (12%). 17c: [R]30 ) -175
D
(c 1.1, CHCl3); IR νmax (CHCl3) 1737, 1677, 1643, 1608 cm-1
;
1H NMR δ 8.19 (dd, 1H, J ) 9.1, 2.1), 7.95 (br s, 1H), 7.73 (d,
1H, J ) 7.9), 7.52 (td, 1H, J ) 7.7, 1.2), 7.36-7.25 (m, 3H),
7.17 (t, 1H, J ) 6.7), 7.11 (t, 1H, J ) 7.4), 7.02 (d, 1H, J )
2.0), 4.93 (dd, 1H, J ) 8.6, 5.0), 3.72 (s, 3H), 3.49 (dd, 1H, J )
14.2, 4.9), 3.22 (dd, 1H, J ) 14.2, 8.5), 2.04-1.85 (m, 3H), 0.86
(d, 1H, J ) 6.2), 0.84 (d, 1H, J ) 5.9); 13C NMR δ 173.3 (CO2-
Me), 160.0 (i-Pr-CdN), 148.5 (Trp-NdC), 141.8, 136.2 (s),
133.3, 127.7 (d), 127.6 (s), 126.2, 125.8, 123.3, 121.8, 119.2 (d),
118.9 (s), 118.7(d), 111.8 (s), 111.3 (d), 59.5 (d), 52.1 (q), 42.9
(t), 29.7 (Trp-CH2), 26.3 (d), 22.3 (q), 22.13(q); 1H-15N
HMBC: three nitrogens were identified at δ 123.4 (indole N),
221.9 (Trp-Nd) and 225.0 (i-Pr-CdN); MS (EI) m/z (relative
intensity %) 403 (M+, 4), 274 (a + H, 20), 130 (b, 100); HRMS
(EI) m/z calcd for C24H25N3O3: 403.1896; found: 403.1884.
N-[2-(2,2-Dim eth yleth yl)-4H-3,1-ben zoxa zin -4-ylid en e]-
L-tr yp top h a n Meth yl Ester (17d ). Following the procedure
given for 17a , 16d (0.204 g, 0.450 mmol) was dehydrated for
6.1 h to give 17d (17%) and recovered 16d (83%). In another
trial, dehydration for 73 h gave 17d and 16d in yields of 22%
quantitatively: IR νmax (CHCl3) 1740, 1678, 1645, 1586 cm-1
;
1H NMR δ 10.96(s, 1H, NH), 8.62 (d, 1H, J ) 8.7), 8.26 (br s,
1H), 7.53 (d, 1H, J ) 7.8), 7.43 (td, 1H, J ) 7.5, 1.2), 7.36 (d,
1H, J ) 8.1), 7.27-7.24 (m, 1H), 7.19 (td, 1H, J ) 7.4, 1.0),
7.09 (t, 1H, J ) 7.3), 6.98 (d, 1H, J ) 2.0), 6.95 (t, 1H, J )
7.8), 6.74 (br d, 1H, J ) 7.4), 5.07 (dt, 1H, J ) 7.4, 5.2), 3.75
(s, 3H), 3.47 (dd, 1H, J ) 13.9, 3.6), 3.43 (dd, 1H, J ) 13.9,
4.0), 2.28-2.18 (m, 3H), 1.01 (d, 1H, J ) 6.4), 1.00 (d, 1H, J )
6.5); 13C NMR δ 172.0, 171.7, 168.5, 139.7, 136.2 (s), 132.8 (d),
127.5 (s), 126.8 (d), 122.9, 122.7, 122.4, 121.4, 119.8 (d), 119.6
(s), 118.4, 111.4 (d), 53.4 (CHN), 52.60 (q), 47.8 (t), 27.4 (t),
26.2 (d), 22.5 (q); MS (EI) m/z (relative intensity %) 421 (M+,
2), 130 (100).
N-[2-(1,1,1-Tr im et h yla cet yla m in o)b en zoyl]-L-t r yp t o-
p h a n Meth yl Ester (16d ). Following the procedure given for
16b, ent-8 was acylated with Me3CCOCl to give 16d quanti-
1
tatively: IR νmax (CHCl3) 1740, 1646, 1586 cm-1; H NMR δ
11.23 (s, 1H, NH), 8.64 (d, 1H, J ) 8.4), 8.17 (br s, 1H, indole-
NH), 7.53 (d, 1H, J ) 7.8), 7.43 (td, 1H, J ) 7.9, 1.5), 7.36(d,
1H, J ) 8.0), 7.25 (dd, 1H, J ) 7.9, 1.5), 7.19 (t, 1H, J ) 7.0),
7.08 (td, 1H, J ) 7.2, 0.9), 6.99 (d, 1H, J ) 2.3), 6.95 (td, 1H,
J ) 7.7, 1.0), 6.71(br d, 1H, J ) 7.5, amide NH), 5.09 (dt, 1H,
J ) 7.5, 5.2), 3.74 (s, 3H), 3.48 (dd, 1H, J ) 14.6, 5.0), 3.44
(dd, 1H, J ) 14.8, 5.0), 1.32 (s, 9H, t-Bu); 13C NMR δ 177.9,
172.0, 168.7, 139.9, 136.2 (s), 132.8 (d), 127.5 (s), 126.8, 122.9,
122.6, 122.4, 121.4 (d), 119.9 (s), 119.8, 118.5, 111.4 (d), 109.6
(s), 53.5, 52.6, 40.2 (s), 27.6 (q), 27.42 (t).
and 78% respectively. 17d : [R]30 ) -129 (c 0.575, CHCl3).
D
IR νmax (CHCl3) 1737, 1673, 1639, 1607 cm-1; H NMR δ 8.19
1
(dd, 1H, J ) 8.0, 1.2), 7.98 (br s, 1H, indole-NH), 7.72 (d, 1H,
J ) 7.8), 7.52 (td, 1H, J ) 7.7, 1.0), 7.36-7.29 (m, 3H), 7.18-
7.06 (m, 2H), 7.12 (d, 1H, J ) 2.0), 4.87 (dd, 1H, J ) 8.1, 5.2),
3.67 (s, 3H), 3.47 (dd, 1H, J ) 14.2, 5.3), 3.32 (dd, 1H, J )
14.3, 8.0), 1.20 (s, 9H); 13C NMR δ 173.1, 165.5, 142.0, 136.1
(s), 133.2, 127.7, 126.2, 126.1, 123.0, 121.8, 119.2, 119.0 (d),
112.2 (s), 111.1 (d), 59.6, 52.0, 37.8 (s), 29.8 (t), 27.4 (q); MS
(EI) m/z (relative intensity %) 403 (M+, 17), 274 ([a + H]+,
70), 130 (b, 100); HRMS (EI) m/z calcd for C24H25N3O3:
403.1896; found: 403.1902.
N -(2-Me t h yl-4H -3,1-b e n zoxa zin -4-ylid e n e )-L-t r yp t o-
p h a n Meth yl Ester (17a ). To a mixture of acetamide 16a
(102 mg, 0.268 mmol), CH2Cl2 (10 mL), Ph3P (354 mg, 1.35
mmol), and I2 (325 mg, 1.28 mmol) was added Et3N (0.37 mL,
2.65 mmol). After being stirred at room temperature for 7 h,
the reaction mixture was diluted with aqueous Na2CO3 and
extracted with CH2Cl2 (×3). After workup, the residue was
purified by flash chromatography (50% AcOEt/hexanes with
1% Et3N) to give 17a (97 mg, 99%) as a syrup: IR νmax (CHCl3)
1740, 1682, 1646, 1587 cm-1; 1H NMR δ 8.18 (dd, 1H, J ) 7.9,
1.4), 7.98 (br s, 1H), 7.51 (td, 1H, J ) 7.7, 1.7), 7.34-7.30 (m,
2H), 7.25(d, 1H, J ) 7.3), 7.17 (td, 1H, J ) 7.0, 1.0), 7.11 (td,
1H, J ) 7.1, 1.1), 6.99 (d, 1H, J ) 2.1), 4.96 (dd, 1H, J ) 8.7,
4.8, Trp-CHN), 3.75 (s, 3H), 3.50 (dd, 1H, J ) 14.1, 4.7), 3.19
(dd, 1H, J ) 14.1, 8.8), 1.76 (s, 3H, Me); 13C NMR δ 173.2 (CO2-
Me), 157.8 (Trp-NdC), 148.3 (Me-CdN), 141.8, 136.2 (s),
133.3, 127.7 (d), 127.7 (s), 126.2, 125.5, 123.3, 121.9, 119.3,
118.8 (d), 118.7 (s), 111.9 (s), 111.2 (d), 59.4 (d), 52.2 (q), 29.6
(S )-2-Me t h y l-r-(1H -in d ol-3-y lm e t h yl)-4-o x o -3(4H )-
qu in a zolin ea cetic Acid Meth yl Ester (18a ). Oxazine 17a
(52.5 mg, 0.145 mmol) was treated with piperidine (0.4 mL)
in CH2Cl2 (1.6 mL) at room temperature for 30 min. The
reaction solution was evaporated to dryness, and the residue
was checked by NMR. 1H NMR showed it contained ca. 70 mol
% of piperidine impurity. The major product was N-[2-((1-
piperidinoethylidene)amino)benzoyl]-L-tryptophan methyl es-
ter, the amidine of 17a : 1H NMR δ 9.73 (d, 1H, J ) 8.0,
CONH), 8.87 (br s, 0.78H), 8.27 (dd, 1H, J ) 8.0, 0.9), 7.48 (d,
1H, J ) 7.9), 7.34-7.25 (m, 2H), 7.08 (t, 1H, J ) 7.2), 7.01
(td, 1H, J ) 7.9, 1.1), 6.99 (td, 1H, J ) 7.6, 0.9), 6.91 (s, 1H),
6.48 (dd, 1H, J ) 8.0, 0.8), 6.32 (br s, 1.34H), 5.21 (dt, 1H, J
) 8.0, 5.8), 3.64 (s, 3H), 3.37 (dd, 1H, J ) 14.5, 5.2), 3.33 (dd,
1H, J ) 14.7, 5.7), 3.13 (br s, 4H, piperidino CH2 × 2), 1.70 (s,
3H), 1.42 (m, 2H, piperidino CH2), 1.26 (br s, 4H, piperidino
CH2 × 2); piperidine impurity: 3.00 (t, 4H, J ) 5.6), 1.77 (m,
4H), 1.58 (m, 2H); 13C NMR δ 176.2 (CO2Me), 166.8 (CONH),
157.7 (-NdCN), 150.5 (s), 136.1 (s), 131.6 (d), 130.8 (d), 127.7
(s), 124.1 (s), 123.6 (d), 123.0 (d), 121.6 (d), 121.5 (d), 119.2
(d), 118.6 (d), 111.2 (d), 110.4 (s), 53.3 (Trp-CHN), 52.1 (OCH3),
45.4 (not observable, identified by HMQC, piperidino NCH2
× 2), 28.1 (Trp-CH2), 25.7 (piperidino CH2 × 2), 24.3 (piperidino
CH2), 15.5 (Me); piperidine impurity: 45.0 (CH2Nx2), 23.2 (CH2
× 2), 22.8 (CH2); 1D NOE: δ 1.70 (Me) f 6.48. 1H-15N
HMBC: four nitrogens were identified at δ 121.6 (Trp-CONH),
125.1 (indole N), 109.6 (piperidino N, correlated with methyl
group at δ 1.70) and 226.0 (NdCN); MS (ESI, positive mode)
m/z 447.1 ([M + H]+).
1
(t), 20.0 (q); H-15N HMBC: three nitrogens were identified
at δ 122.2 (indole N), 223.0 (correlated with protons at δ 4.96,
3.50, and 3.19) and 224.2 (Trp-Nd, correlated with protons at
δ 1.76 and 7.25); MS (EI) m/z (relative intensity %) 361 (M+,
54), 231 (a, 64), 130 (b, 100).
N -(2-P h e n yl-4H -3,1-b e n zoxa zin -4-ylid e n e )-L-t r yp t o-
p h a n Meth yl Ester (17b). Following the procedure given for
17a , 16b was dehydrated for 1.4 h. Purification by preparative
TLC (5% MeOH/CH2Cl2) afforded product 17b (44 mg, 82%)
and recovered 16b (6 mg, 11%, due to decomposition of 17b).
17b: IR νmax (CHCl3) 1737, 1675, 1627, 1605 cm-1; 1H NMR δ
8.26 (dd, 1H, J ) 8.0, 1.3), 7.95-7.91(m, 3H), 7.75 (dd, 1H, J
) 6.7, 1.8), 7.58 (td, J ) 7.7, 1.4), 7.50-7.44 (m, 3H), 7.40-
7.34 (m, 3H), 7.28-7.23 (m, 1H), 7.16-7.05 (m, 3H), 5.05 (dd,
1H, J ) 8.0, 5.3), 3.71 (s, 3H), 3.56 (dd, 1H, J ) 14.3, 5.4),
3.34 (dd, 1H, J ) 14.1, 8.0); 13C NMR δ 173.2, 154.6, 148.3,
142.2, 136.1 (s), 133.3, 131.9 (d), 130.6 (s), 128.5, 127.9, 127.7
(d), 127.5 (s), 126.5, 126.4, 123.0, 121.9, 119.24 (d), 119.18 (s),
118.8 (d), 112.0 (s), 111.2 (d), 60.1, 52.1, 29.8 (t); 1H-15N
HMBC: three nitrogens were identified at δ 121.7 (indole N),
222.6 and 223.4 (Trp-Nd); MS (ESI, positive mode) m/z 424.0
([M + H]+).
The above crude amidine (0.069 mmol) was refluxed in
MeCN/1,2-dichloroethane (5/5 mL) for 15 h to give 18a in 93%
yield. 18a : [R]30 ) -457 (c 0.44, CHCl3){lit,13b [R]20 ) -555
D
D
(c 0.2, acetone); IR νmax (KBr) 3478, 1747, 1675, 1596 cm-1; 1H
NMR δ 8.28 (dd, 1H, J ) 8.0, 1.1), 8.23 (br s, 1H, NH), 7.72
(ddd, 1H, J ) 8.3, 7.0, 1.4), 7.53 (d, 1H, J ) 7.8), 7.51 (d, 1H,
J ) 7.5), 7.46 (td, 1H, J ) 7.6, 1.0), 7.30 (d, 1H, J ) 7.8), 7.16
(td, 1H, J ) 7.6, 1.0), 7.05 (ddd, 1H, J ) 7.9, 7.1, 0.9), 6.66 (d,
1H, J ) 1.9), 4.90 (br s, 1H), 3.87(dd, 1H, J ) 15.2, 3.8), 3.79
(s, 3H), 3.73 (dd, 1H, J ) 15.1, 10.4), 1.89 (s, 3H); 13C NMR δ
169.4 (CO2Me), 161.7 (CON), 154.5 (NdCN), 147.1, 136.1 (s),
N-[2-(2-Meth ylp r op yl)-4H-3,1-ben zoxa zin -4-ylid en e]-L-
tr yp top h a n Meth yl Ester (17c). Following the procedure
given for 17a , 16c was dehydrated for 20 h to give 17c

1030 J . Org. Chem., Vol. 65, No. 4, 2000
Wang and Ganesan
134.6 (d), 126.9 (s), 126.7, 126.6, 126.6, 123.2, 122.4 (d), 120.6
(s), 119.9, 117.8, 111.5 (d), 110.7 (s), 60.5, 52.8 (q), 23.2 (q);
1D NOE: δ 1.89 (Me) f 5.21 (Trp-CHN); 1H-15N HMBC:
three nitrogens were identified at δ 124.0 (indole N), 171.6
(CON), and 239.3 (NdC); MS (ESI, positive mode) m/z 362.4
([M + H]+).
N-(2-Cya n op h en yl)qu in olin e-2-ca r boxa m id e (21). Fol-
lowing the procedure given for 16a , 20 (0.207 g, 0.710 mmol)
was dehydrated for 8 h. The reaction mixture was purified by
preparative TLC (30% AcOEt in hexanes) to give the nitrile
21 (103 mg, 53%) as a pale yellow solid: IR νmax (KBr) 3261,
2219, 1697, 1582, 1533 cm-1; 1H NMR δ 11.07 (s, 1H, CONH),
8.72 (d, 1H, J ) 9.0), 8.33 (d, 1H, J ) 8.5), 8.30 (d, 1H, J )
8.5), 8.20 (d, 1H, J ) 8.5), 7.86 (d, 1H, J ) 8.2), 7.76 (ddd, 1H,
J ) 7.5, 6.9, 1.5), 7.65-7.59 (m, 3H), 7.19 (td, 1H, J ) 7.7,
1.0); 13C NMR δ 162.5, 148.4, 146.2, 140.6 (s), 138.0, 134.2,
132.5, 130.5, 130.2 (d), 129.6 (s), 128.6, 127.6, 123.9, 120.2,
118.4 (d), 116.4 (CN), 102.2 (s); MS (ESI, positive mode) m/z
274.2 ([M + H]+).
Meth yl 9H-1-[2-((1,1,1-Tr im eth yl)a cetyla m in o)p h en yl]-
p yr id o[3,4-b]in d ole-3-ca r boxyla te (19). The mixture of 16d
(53 mg, 0.126 mmol), (CH2Cl)2 (4 mL), Ph3P (164 mg, 0.625
mmol), I2 (154 mg, 0.606 mmol), and Et3N (0.175 mL, 1.26
mmol) was stirred at room temperature for 1 h, and TLC
showed only a very small amount of product formed. The
reaction mixture was heated at reflux for 4 h, and then the
black solution was quenched with aqueous Na2CO3 and
extracted with CH2Cl2 (×3). After workup, the residue was
purified by flash chromatography (50% AcOEt/hexanes), and
the desired fractions were purified by preparative TLC (2%
MeOH/CH2Cl2) to give oxazine 17d (6 mg, 12%) and 19 (39
mg, 77%). 19: white solid, fluorescent under UV 365 nm; IR
Ack n ow led gm en t. This work was supported by
grants from the National Science and Technology Board
of Singapore. We thank Mrs. Xu Xiaoli and Dr. Wang
Yue of the Institute of Molecular and Cell Biology for
antimicrobial screening, and the Drug Synthesis and
Screening branch of the NCI for antitumor testing.
1
νmax (KBr) 3237, 1731, 1664, 1518 cm-1; H NMR δ 10.96 (s,
1H, CONH), 10.66 (s, 1H, indole NH), 8.92 (s, 1H, C4-H), 8.25
(d, 1H, J ) 7.9), 8.08 (d, 1H, J ) 8.2), 7.77 (d, 1H, J ) 8.2),
7.74 (dd, 1H, J ) 7.7, 1.4), 7.66 (td, 1H, J ) 7.2, 1.0), 7.41 (td,
1H, J ) 7.1, 0.7), 6.94 (td, 1H, J ) 7.5, 1.1), 6.83 (td, 1H, J )
7.8, 1.4), 4.05 (s, 3H), 1.27 (s, 9H); 13C NMR δ 177.5 (CONH),
166.2 (CO2Me), 141.4, 141.3, 136.1, 135.9, 135.4, 130.5 (s),
130.0, 129.0, 128.6 (d), 126.0 (s), 123.6, 123.6, 121.8 (d), 121.7
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
12, 14c, 15, epimer of 15, 16a -c, 17b, and amidine of 17a ,
and 13C NMR spectra for 14a , 16d , 17a ,c,d , 19, and 21. This
material is available free of charge via the Internet at
http://pubs.acs.org.
1
(s), 121.1, 117.3, 112.7 (d), 52.4 (q), 39.7 (s), 27.5 (q); H-15N
HSQC and HMBC: three nitrogens were identified at δ 119.4
(CONH), 118.4 (indole N), and 292.8 (â-carboline -CdN-);
MS (EI) m/z (relative intensity %) 401 (M+, 28), 344
([M - t-Bu]+, 100).
J O9914364