Synthesis of Marine Sponge Alkaloids Oroidin, Clathrodin, and Dispacamides. Preparation and Transformation of 2-Amino-4,5-dialkoxy-4,5-dihydroimidazolines from 2-Aminoimidazoles

Article abstract of DOI:10.1021/jo9718298

The preparation and transformation of 2-amino-4,5-dialkoxy-4,5-dihydroimidazolines A from 2-aminoimidazoles (AIs) is described. The oxidation of 2-aminoimidazole 8 with NCS in methanol affords cyclic guanidine adduct 9 which, upon heating, affords vinylogous AI derivative 3 and 2-aminoimidazolinone (glycocyamidine) 13. Olefin 3 comprises the core structure found in the oroidin alkaloids. Furthermore, oxidation of 8 with Br₂ and DMSO affords directly α,β-unsaturated imidazolinone 14 which is the key structural unit comprising the dispacamides (2). A highly facile and practical synthesis of the C₁₁N₅ marine sponge alkaloids oroidin (1a), clathrodin (1c), and dispcamides (2) is outlined.

Full text of DOI:10.1021/jo9718298

1248
J . Org. Chem. 1998, 63, 1248-1253
Syn th esis of Ma r in e Sp on ge Alk a loid s Or oid in , Cla th r od in , a n d
Disp a ca m id es. P r ep a r a tion a n d Tr a n sfor m a tion of
2-Am in o-4,5-d ia lk oxy-4,5-d ih yd r oim id a zolin es fr om
2-Am in oim id a zoles
Anne Olofson, Kenichi Yakushijin, and David A. Horne*
Department of Chemistry, Columbia University, New York, New York 10027
Received October 3, 1997
The preparation and transformation of 2-amino-4,5-dialkoxy-4,5-dihydroimidazolines A from
2-aminoimidazoles (AIs) is described. The oxidation of 2-aminoimidazole 8 with NCS in methanol
affords cyclic guanidine adduct 9 which, upon heating, affords vinylogous AI derivative 3 and
2-aminoimidazolinone (glycocyamidine) 13. Olefin 3 comprises the core structure found in the
oroidin alkaloids. Furthermore, oxidation of 8 with Br2 and DMSO affords directly R,â-unsaturated
imidazolinone 14 which is the key structural unit comprising the dispacamides (2). A highly facile
and practical synthesis of the C11N5 marine sponge alkaloids oroidin (1a ), clathrodin (1c), and
dispacamides (2) is outlined.
Marine sponges of the genera Agelas, Hymeniacidon,
groups.8,9 Both groups focused on the preparation of 3 in
which Wittig chemistry was used to install the olefinic
double bond. Moreover, the syntheses relied heavily on
the use of protecting groups on nitrogen. Undoubtedly,
alkaloids 1-3 are biogenetically related and likely de-
rived from a common 2-aminoimidazole (AI) precursor.
In this report, we describe the facile synthesis of 1, 2,
and 3 by the preparation and rearrangement of 2-amino-
4,5-dialkoxy-4,5-dihydroimidazolines having the general-
ized structure A.10
and Phakellia produce a structurally diverse and phar-
macologically interesting class of C11N5, and dimerically
related, secondary metabolites.1,2 The chemical features
that distinguish these alkaloids are the presence of either
a brominated or nonbrominated pyrrole carboxamide
unit, a 2-aminoimidazole or glycocyamidine nucleus, and
a functionalized or unfunctionalized 3-carbon alkyl chain
connecting these heterocyclic moieties. Collectively, this
group of natural products is known as the oroidin
alkaloids of which oroidin (1a )3 and dispacamide (2a ),4
both from the sponge Agelas sp., represent the “simplest”
structural entities. The related monobromopyrrole de-
rivatives, hymenidin (1b),5 from the sponge Hymeniaci-
don sp., and monobromodispacamide (2b)4 are also
known, as well as the debromooroidin derivative, clath-
rodin (1c).6 Metabolites 1b and 2 have been reported as
potent antagonists of serotonergic5 and histaminergic4
receptors, respectively. Closely related to oroidin (1a ) is
3-amino-1-(2-aminoimidazol-4-yl)prop-1-ene (3)7 which
lacks the pyrrole moiety. This derivative has been
isolated from the Axinellidae sponges T. morchella and
P. walpersi and is a potential biosynthetic precursor to
oroidin-related metabolites. A synthesis of oroidin (1a )
and clathrodin (1c) has been reported by two research
*
To whom correspondence should be addressed. Tel. (212)-854-
8634. Fax (212)-932-1289. email: horne@chem.columbia.edu.
(1) For reviews, see: (a) Kobayashi, J .; Ishibashi, M. In The
Alkaloids: Chemistry and Pharmacology; Brossi, A., Ed.; Academic
Press: New York, 1992; Vol. 41, pp 41-124. (b) Faulkner, D. J . Nat.
Prod. Rep. 1996, 13, 75. (c) Berlinck, R. G. S. Nat. Prod. Rep. 1996,
13, 377.
(2) For recent reports, see: (a) Tsukamoto, S.; Kato, H.; Hirota, H.;
Fusetani, N J . Nat. Prod. 1996, 59, 501. (b) Cafieri, F.; Fattorusso, E.;
Mangoni, A.; Taglialatela-Scafati, O. Tetrahedron 1996, 52, 13713.
(3) (a) Forenza, S.; Minale, L.; Riccio, R.; Fattorusso, E. J . Chem.
Soc., Chem. Commun. 1971, 1129. (b) Garcia, E. E.; Benjamin, L. E.;
Fryer, R. I. J . Chem. Soc., Chem. Commun. 1973, 78.
(4) Cafieri, F.; Fattorusso, E.; Mangoni, A.; Taglialatela-Scafati, O.
Tetrahedron Lett. 1996, 37, 3587.
Imidazolines of the type A can be considered dialkoxy
adducts of cyclic guanidines. In unpublished investiga-
tions from the Bu¨chi group, 4,5-dimethoxyimidazolines
were obtained from the reaction of 4-acyl-2-aminoimida-
zoles with NBS in methanol.10 A search of the literature
revealed no additional examples. Although known, a
(8) Webber, S. E.; Little, T. L. J . Org. Chem. 1994, 59, 7299.
(9) (a) de Nanteuil, G.; Ahond, A.; Poupat, C.; Thoison, O.; Potier,
P. Bull. Soc. Chim. Fr. 1986, 813. (b) Daninos, S.; Al Mourabit, A.;
Ahond, A.; Zurita, M. B.; Poupat, C.; Potier, P. Bull. Soc. Chim. Fr.
1994, 131, 590. (c) Daninos-Zeghal, S.; Al Mourabit, A.; Ahond, A.;
Poupat, C.; Potier, P. Tetrahedron 1997, 53, 7605.
(5) Kobayashi, J .; Ohizumi, Y.; Nakamura, H.; Hirata, Y. Experientia
1986, 42, 1176.
(6) Morales, J . J .; Rodriguez, A. D. J . Nat. Prod. 1991, 54, 629.
(7) Wright, A. E.; Chiles, S. A.; Cross, S. S. J . Nat. Prod. 1991, 54,
1684.
(10) Dupriest, M. Ph.D. Thesis, Massachusetts Institute of Technol-
ogy, 1982.
S0022-3263(97)01829-X CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/27/1998

Synthesis of C11N5 Marine Alkaloids
J . Org. Chem., Vol. 63, No. 4, 1998 1249
Sch em e 1
Sch em e 2
small number of related dihydroxy adducts have been
isolated from the condensation of guanidines and R-dike-
tones11 and/or glyoxal.12 These limited examples il-
lustrate the stability of imidazoline adducts to isolation.
In a continuing effort toward the development of AI
chemistry,13 we focused on further investigating the
preparation of various analogues of A and examining
their utility as key intermediates in alkaloid synthesis.
The belief was that these adducts could serve as useful
precursors to various members of the oroidin family of
marine natural products.
Our initial investigations focused on the direct genera-
tion of adduct A by examining various conditions for the
oxidation of functionalized AI substrates (Scheme 1). The
trapping of a reactive intermediate by nucleophilic
solvent molecules was the objective. Since a number of
AI derivatives are readily available from known proce-
dures,14 this overall approach would provide a general
method for the preparation of 2-amino-4,5-dialkoxy-4,5-
dihydroimidazoline derivatives. Although few in num-
ber, related examples in the literature involving the
addition to the 4,5-double bond of AIs can be seen in the
intramolecular oxidative cycloaddition used for the bio-
mimetic synthesis of dibromophakellin,15 the intermo-
lecular [2 + 4] cycloaddition for the preparation of
tetrahydropurine derivatives,16 and the acid-facilitated
addition of EtOH to a bicyclic[3.3.0] AI system to give a
stable 2-aminoimidazolidinium cation.8
Preliminary investigations focused on AI (Scheme 2).
Upon treatment of AI sulfate with N-chlorosuccinimide
in methanol, a swift and clean reaction occurred that
afforded trans adduct 4 in excellent yield along with trace
amounts of the cis diastereomer. With benzyl alcohol,
however, a 6:1 trans:cis mixture of adduct 5 was obtained
wherein π-stacking of the phenyl rings may contribute
to the overall stability of the cis isomer. The use of
ethylene glycol produced trans adduct 6 (and trace
amounts of cis) as well as the bicyclic imidazoline deriv-
ative 7 as a minor coproduct. This bicyclic product can
be obtained in pure form as a colorless solid by crystal-
lization from ethanol after which 6 is separated as an
oil. Generally, imidazoline adducts are obtained by
trituration from the reaction mixture and are relatively
stable. In each instance, the predominant diastereomer
formed was the trans isomer except in the case of the
bicyclic [4.3.0] imidazoline derivative 7 where the ring
fusion is cis. The stereochemistry of the adducts was
1
determined from H NMR data. Previous data on related
systems established that the 4,5-imidazoline proton
resonances for the trans isomers are upfield from those
of the cis.12 In DMSO-d6, trans adducts 4-6 produce
singlets at δ 4.86, 5.10, and 4.96, respectively, whereas
for the corresponding cis isomers, singlets were observed
at lower field at δ 5.12, 5.38, and 5.20, respectively. The
reactions in Scheme 2 were model reactions for the study
of 2-amino-4-(3-aminopropyl)-1H-imidazole 8 and dihy-
drooroidin 15,15 which bear alkylamine and pyrrole-
caboxamide functionalities, respectively.
AI derivative 8 can be considered a hypothetical
forerunner to the C11N5 natural products 1 and 2. It can
be prepared readily from ornithine methyl ester using
the method of Lancini et al.17 This procedure, which
incorporates an Akabori reduction followed by condensa-
tion of the resulting R-amino aldehyde with cyanamide,
allows for the preparation of multigram quantities of
2-aminoimidazoles from esters of R-amino acids. Oxida-
tion of 8 with NCS in methanol gave the expected trans
dimethoxy adduct 9 in good yield (Scheme 3). An
interesting reversal from the model reactions in Scheme
2 is seen with ethylene glycol. When 8 was treated with
NCS in ethylene glycol, bicyclic adduct 10 was produced
as the only product without formation of the correspond-
ing disubstituted adduct. Evidently, steric interactions
between the aminopropyl side chain and the formation
of the incipient ethylene glycol unit preclude the genera-
tion of the bisglycol adduct.
(11) (a) Nishimura, T.; Nakano, K.; Shibamoto, S.; Kitajima, K. J .
Heterocycl. Chem. 1975, 12, 471. (b) Nishimura, T.; Kitajima, K. J .
Org. Chem. 1976, 41, 1590. (c) Nishimura, T.; Kitajima, K. J . Org.
Chem. 1979, 44, 818.
(12) McClelland, R. A.; Panicucci, R.; Rauth, A. M. J . Am. Chem.
Soc. 1987, 109, 4308.
(13) (a) Xu, Y.-z.; Yakushijin, K.; Horne, D. A. J . Org. Chem. 1997,
62, 456 (and earlier references). (b) Olofson, A.; Yakushijin, K.; Horne,
D. A. J . Org. Chem. 1997, 62, 7918.
(14) Methodologies for the preparation of 2-aminoimidazoles are
described in ref 8.
The trans stereochemistry of adduct 9 was confirmed
by 1-D selective NOESY experiments. Irradiation of the
C5 ring proton singlet at 4.73 ppm showed NOEs to both
methoxyl groups at 3.35 and 3.15 ppm. No enhancement
was observed to the methylene protons of the aminopro-
pyl side chain at 1.5-1.9 ppm. Likewise, when the C5
methoxyl group (geminal to the ring proton) was irradi-
(15) Foley, L. H.; Bu¨chi, G. J . Am. Chem. Soc. 1982, 104, 1776.
(16) Xu, Y.-z.; Yakushijin, K.; Horne, D. A. Tetrahedron Lett. 1993,
34, 6981.
(17) (a) Lancini, G. C.; Lazzari, E. J . Heterocycl. Chem. 1966, 3, 152.
(b) Lancini, G. C.; Lazzari, E.; Arioli, V.; Bellani, P. J . Med. Chem.
1969, 12, 775.

1250 J . Org. Chem., Vol. 63, No. 4, 1998
Olofson et al.
Sch em e 3a
a
Key: (a) NCS, MeOH, rt, 83%; (b) NCS, ethylene glycol, rt, 80%; (c) MeOH, reflux, 11 (30%), 12 (15%); (d) 135 °C, m-xylene/methanol,
3 (55%), 13 (35%); (e) 2-(trichloroacetyl)pyrrole, DMF, rt, 75%; (f) Br2, DMSO, rt, 68%; (g) 4-bromo-2-(trichloroacetyl)pyrrole, DMF, rt,
65%; (h) Br2, CH3SO3H, 85 °C, 71%.
ated, an NOE was seen only to the ring proton and the
geminal guanidine N1 proton, which resonated at 9.70
ppm. No enhancement was observed for the adjacent C4
methoxyl group. Irradiation of the C4 methoxyl group
showed NOEs to both the C5 ring proton and the geminal
guanidine N3 proton, but again, no NOE was observed
to the vicinal C5 methoxyl group. These data establish
the stereochemical relationship of the methoxyl groups
as trans.
In the course of these reactions, the mechanistic
pathway leading to adduct A probably involves initial
incorporation of halogen to AI followed by substitution
with nucleophilic solvent (Scheme 1). The trans dialkoxy
adduct 9 predominates thus implicating the formation
of intermediate B with the stepwise addition of another
ROH from the least hindered face.
An interesting feature of these adducts is their poten-
tial for rearrangement. This was investigated thermally
by heating adducts 9 and 10 (Scheme 3). Refluxing 9 in
methanol afforded mainly the R-substituted side chain
derivative 11 and unchanged starting material. Similar
results were seen with adduct 10 in refluxing methanol
which gave the mixed side chain derivatives 11 and 12
along with a significant amount of recovered starting
material. At elevated temperatures (135 °C) using an
initial 1:1 solvent mixture of xylene:methanol,18 adduct
9 rearranged to two products, namely, vinyl imidazole 3
and imidazolinone 13 in 55% and 35% yields, respec-
tively. Acylation of 3 with 2-(trichloroacetyl)pyrrole19
afforded clathrodin (1c). All spectral data of synthetic
1c and 3 were in satisfactory agreement with those
reported for the natural material.6,7
Next, the formation of the R,â-unsaturated imidazoli-
none ring system which comprises the dispacamides (2)
was investigated. This was done using both AI derivative
8 and imidazolinone 13. Derivative 8 requires a 2-fold
oxidation of the AI nucleus to install both the carbonyl
and olefin functionalities. Since the ability of adduct
formation occurs readily upon oxidation in protic sol-
vents, similar additions were envisaged with the aprotic
but nucleophilic solvent DMSO.20 The addition of DMSO
followed by elimination of dimethyl sulfide would lead
directly to the R,â-unsaturated imidazolinone ring system
found in the dispacamides. When 8 was treated with 1
equiv of Br2 in DMSO, transformation to (Z)-R,â-unsatur-
ated imidazolinone 14 resulted in good yield.21 The Z
stereochemistry of olefin 14 was firmly established by
its conversion to monobromodispacamide (2b) by acyla-
tion with 4-bromo-2-(trichloroacetyl)pyrrole.22 All spec-
tral data of synthetic 2b were in satisfactory agreement
with those reported for the natural product.4,23 Alterna-
tively, 14 can be produced from the oxidation of imida-
zolinone 13 with Br2 in methanesulfonic acid.
Acylation of AI derivative 8 with the requisite dibro-
mopyrrole unit produced dihydrooroidin (15) in 65% yield.
This compound is also capable of forming dialkoxy
adducts, but the presence of the pyrrolecarboxamide unit
necessitated modification of the reaction conditions
(Scheme 4). The amide linkage in 15 interferes with
(20) (a) Savige, W. E.; Fontana, A. J . Chem. Soc. Chem. Commun.
1976, 599. (b) Szabo-Pusztay, K.; Szabo, L. Synthesis 1979, 276.
(21) The presence of a small amount (5-10%) of the E-isomer can
be seen in the 1H NMR spectrum (D2O): δ 3.05 (dt, 2H, J ) 8.0, 7.1),
3.15 (t, 2H, J ) 7.1), 6.06 (t, 1H, J ) 8.0).
(22) Keifer, P. A.; Schwartz, R. E.; Koker, M. E. S.; Hughes, R. G.,
J r.; Rittschof, D.; Rinehart, K. L. J . Org. Chem. 1991, 56, 2965.
(23) The presence of a small amount (5-10%) of the E-isomer can
be seen in the 1H NMR spectrum (CD3OD): δ 2.98 (dt, 2H, J ) 8.2,
6.6), 3.48 (t, 2H, J ) 6.6), 6.06 (t, 1H, J ) 8.2), 6.74 (d, 1H, J ) 1.5),
6.90 (d, 1H, J ) 1.5).
(18) The reaction was heated without a condenser, thus allowing
the methanol to boil off.
(19) Bailey, D. M.; J ohnson, R. E.; Albertson, N. F. Org. Synth. 1971,
51, 100.

Synthesis of C11N5 Marine Alkaloids
J . Org. Chem., Vol. 63, No. 4, 1998 1251
Sch em e 4a
a
Key: (a) Br2, tBuOK, CH3OH, -78 °C, 75%; (b) 135 °C, m-xylene/MeOH, 1a (48%), 17 (30%); (c) Br2, DMSO, 60%.
NMR (DMSO-d6) δ 158.6 (s), 90.3 (d × 2), 54.7 (q × 2); IR (KBr)
adductformation under the usual conditions of NCS and
methanol. This is due to competing intramolecular
processes of the pyrrolecarboxamide group. To overcome
this problem, a slight excess of base (tBuOK) was added
and bromine was used instead of NCS as the halogen
source. The slight excess of base generates the more
nucleophilic methoxide species which readily adds to the
oxidized AI nucleus. This afforded dimethoxy adduct 16
in good yields. The trans stereochemical assignment of
adduct 16 was inferred from comparison with NMR data
of trans adduct 9. Adduct 16 can be converted to oroidin
(1a ) and dihydrodispacamide (17) when heated in xylene/
methanol. In addition, oxidation of dihydrooroidin (15)
with Br2 and DMSO gave dispacamide 2a . Starting from
commercially available ornithine methyl ester, the overall
synthesis of 1 and 2 required only four and three steps,
respectively, and proceeded without the use of a single
protecting group on nitrogen. AI derivative 8 serves as a
common intermediate to metabolites 1-3.
3153, 2822, 1700, 1583, 1211 cm-1; MS m/z (relative intensity)
146 (M+ + 1, 100), 114 (10). Anal. Calcd for C5H11N3O2‚1/
2H2SO4: C, 30.92; H, 6.23; N, 21.64. Found: C, 30.89; H, 6.25;
N, 21.60.
tr a n s-2-Am in o-4,5-d ih yd r o-4,5-ibs(ben zyloxy)-2-im id a -
zolin e (5). To a stirred mixture of AI sulfate (0.60 g, 4.5
mmol) in 10 mL of benzyl alcohol at rt was added NCS (0.67
g, 5.0 mmol). After 20 h, the reaction mixture was diluted
with ether and decanted (3 × 100 mL). The resulting residue
was dissolved in 10 mL of acetone, and the small amount of
unreacted starting material was removed by filtration. Con-
centration of the filtrate afforded a gum that was washed with
ether (100 mL) and dried to give 5 as a pale yellow oil (1.26 g,
80%). The 1H NMR of 5 showed 15% of cis isomer. 5: 1H NMR
(DMSO-d6) δ 9.78 (bs, 2H), 8.49 (bs, 2H), 7.34 (m, 10H), 5.10
(s, 2H), 4.64 (d, 2H, J ) 11.7), 4.55 (d, 2H, J ) 11.7); 13C NMR
(DMSO-d6) δ 158.8 (s), 137.0 (s × 2), 128.4 and 128.0 (d × 10),
89.1 (d × 2), 68.8 (t × 2); IR (Nujol) 3194, 2851, 1695, 1576,
1093 cm-1; MS m/z (relative intensity) 298 (M+ + 1, 100), 208
(60), 190 (10). HRMS calcd for C17H20N3O2 (MH+) 298.1557,
found 298.1551.
In conclusion, the preparation of 2-amino-4,5-dialkoxy-
4,5-dihydroimidazoline derivatives having various func-
tionalities from 2-aminoimidazoles is described. The
method appears general, and the utility of these interest-
ing derivatives is demonstrated in their imidazoline to
vinyl imidazole and imidazolinone transformations. The
facile synthesis of 1, 2, and 3 is illustrative of the
chemistry. Furthermore, we have shown that the AI
nucleus can serve as a direct precursor to the R,â-
unsaturated imidazolinone system found in the dispaca-
mides and related AI alkaloids. Perhaps a similar
oxidative pathway is operative in the biogenesis of
glycocyamidine-containing metabolites such as 2.
tr a n s-2-Am in o-4,5-d ih yd r o-4,5-bis(2-h yd r oxyeth oxy)-
2-im id a zolin e (6) a n d 6-Am in o-5H -im id a zo[4,5-b]-1,4-
d ioxa n e (7). To a stirred mixture of AI sulfate (0.60 g, 4.5
mmol) in 10 mL of ethylene glycol at rt was added NCS (0.67
g, 5.0 mmol). After 20 h, the reaction mixture was diluted
with ether and decanted (3 × 100 mL). The resulting residue
was washed with acetone (3 × 100 mL) to give a mixture of 6
1
and 7 (0.7 g, 80%) as a colorless oil. The H NMR in DMSO-
d6 showed a 6:1 ratio of 6:7 with a trace amount of the cis
isomer of 6. Addition of a small amount of ethanol to this oil
and filtration gave pure 7 as a colorless solid. The filtrate,
after evaporation, yielded a colorless oil consisting of 6 with a
trace of 7. 6: 1H NMR (DMSO-d6) δ 9.64 (bs, 2H), 8.44 (bs,
2H), 4.96 (s, 2H), 4.85 (br, 2H), 3.51 (m × 2, 8H); 13C NMR
(DMSO-d6) δ 158.7 (s), 89.8 (d × 2), 69.1 (t × 2), 60.0 (t × 2).
7: 1H NMR (DMSO-d6 ) δ 9.08 (bs, 2H), 8.48 (bs, 2H), 5.31 (s,
2H), 3.69 (m, 4H); 1H NMR (D2O) δ 5.46 (s, 2H), 3.90 (ddd,
2Heq, J ) 8.4, 7.1, 6.9), 3.82 (ddd, 2Hax, J ) 8.4, 7.1, 6.9); 13C
NMR (DMSO-d6) δ 159.2 (s), 78.8 (d × 2), 58.0 (t × 2); IR (KBr)
3180, 2956, 1700, 1667, 1261 cm-1; MS m/z (relative intensity)
143 (M+, 45), 114 (30), 86 (100). Anal. Calcd for
C5H9N3O2‚1/2H2SO4: C, 31.25; H, 5.24; N, 21.86. Found: C,
31.30; H, 5.27; N, 21.87.
2-Am in o-4-(3-a m in op r op yl)-1H-im id a zole (8). A solu-
tion of L-ornithine methyl ester dihydrochloride (25 g, 0.11 mol)
in 250 mL of water was cooled between 0 and 5 °C. The pH
was adjusted to 1.5-2.0 by addition of 15% HCl. Over the
course of 1 h, 5% Na/Hg (546 g, 1.1 mol) was added to the
solution while the temperature and pH within were main-
tained the given range. When the pH remained constant and
the evolution of gas had ceased, the solution was decanted to
remove Hg. The pH was then adjusted to 4.3 by the addition
of 1 N NaOH. Cyanamide (48 mL, 0.57 mol) was added and
the solution heated at 95 °C for 2.5 h. Removal of the solvent
in vacuo afforded a thick, light yellow residue which was
Exp er im en ta l Section
Gen er a l. Unless otherwise noted, materials were obtained
from commercial suppliers and used without further purifica-
tion except for solvents which were dried and distilled. Silica
gel (particle size 32-63 µ) was used for flash chromatography.
1H NMR spectra were measured at 300 MHz. 13C NMR
spectra were recorded at 75 MHz. Abbreviations are as
follows: AI ) 2-aminoimidazole and NCS ) N-chlorosuccin-
imide.
tr a n s-2-Am in o-4,5-d ih yd r o-4,5-d im et h oxy-2-im id a zo-
lin e (4). To a stirred solution of AI sulfate (0.60 g, 4.5 mmol)
in 10 mL of methanol at rt was added NCS (0.67 g, 5.0 mmol).
After 30 min, methanol was removed by evaporation under
reduced pressure without heat. The resulting residue was
washed with ether (3 × 100 mL) and acetone (100 mL), and
the solid was collected by filtration to give 4 as a colorless solid
1
(0.84 g, 95%). The H NMR of 4 showed trace amounts of cis
isomer. 4: 1H NMR (DMSO-d6) δ 9.56 (s, 2H), 8.35 (s, 2H),
4.86 (s, 2H), 3.30 (s, 6H); (D2O) δ 5.03 (s, 2H), 3.39 (s, 6H); 13
C

1252 J . Org. Chem., Vol. 63, No. 4, 1998
Olofson et al.
washed with ether (3 × 200 mL). Methanol was added to the
residue and NaCl removed by filtration. The filtrate, after
evaporation, gave a pale yellow solid. Recrystallization from
ethanol gave 8 as colorless needles (14.9 g, 62%): mp 213-215
°C; 1H NMR (DMSO-d6) δ 12.30 (s, 1H), 11.76 (s, 1H), 8.25 (s,
3H), 7.39 (s, 2H), 6.62 (s, 1H), 2.72 (t, 2H, J ) 6.3), 2.5 (t, 2H,
residue washed with ether (3 × 100 mL) and acetone (2 × 100
mL). Addition of 5 mL of methanol to the residue and
filtration yielded pure 3‚2HCl as a colorless solid (0.46 g, 40%).
Concentration of the filtrate followed by purification of the
resulting residue by flash chromatography (CH2Cl2/MeOH
saturated with NH3 1:1) afforded additional 3 (0.11 g, 15%)
and 13 (0.30 g, 35%) as free bases. Addition of concentrated
HCl to a methanol solution of the corresponding free base
and concentration in vacuo afforded 3‚2HCl and 13‚2HCl.
3‚2HCl: 1H NMR (DMSO-d6) δ 12.99 (br, 1H), 12.2 (br, 1H),
8.40 (bs, 3H), 7.58 (s, 2H), 7.01 (s, 1H), 6.47 (d, 1H, J ) 16.1),
6.11 (dt, 1H, J ) 16.1, 6.3), 3.53 (bs, 2H, changes to do with
D2O, J ) 6.3); 1H NMR (CD3OD) δ 6.93 (s, 1H), 6.59 (s, 1H, J
) 16.1), 6.16 (dt, 1H, J ) 16.1 and 7.0), 3.70 (d, 2H, J ) 7.0);
13C NMR (CD3OD) δ 149.5 (s), 125.9 (s), 123.1 (d), 121.5 (d),
114.0(d), 42.1 (t); UV λmax (MeOH) 265 nm; MS m/z (relative
intensity) 139 (M+ + 1, 100), 122 (30). Anal. Calcd for
C6H10N4‚2HCl: C, 34.14; H, 5.73; N, 26.54. Found: C, 33.99;
H, 5.70; N, 26.53. 13‚2HCl: 1H NMR (DMSO-d6) δ 12.37 (bs,
1H), 9.87 (s, 1H), 9.18 (bs, 1H), 8.91 (bs, 1H), 8.02 (bs, 3H),
4.34 (t, 1H, J ) 5.1), 2.78 (q, 2H, J ) 6.5), 1.86-1.55 (m, 4H,
J ) 7.7); 13C NMR (DMSO-d6) δ 174.9 (s), 157.9 (s), 58.5 (d),
38.4 (t), 27.6 (t), 22.4 (t); IR (KBr) 3283, 2644, 1713, 1545, 1397
cm-1; UV λmax (MeOH) 205 nm; MS m/z (relative intensity)
157 (M+ + 1, 100), 102 (10). Anal. Calcd for C6H12N4O‚2HCl:
C, 31.45; H, 6.16; N, 24.45. Found: C, 31.39; H, 6.12; N, 24.50.
(Z)-2-Am in o-5-(3-a m in op r op ylid en yl)-2-im id a zolin -4-
on e (14). Meth od A. To a stirred solution of 13‚2HCl (0.10
g, 0.44 mmol) in 1 mL of CH3SO3H was added bromine (20
µL, 0.44 mmol). The reaction was heated between 80 and 90
°C for 1 h. After cooling, the reaction mixture was diluted
with ether and decanted (3 × 25 mL). The resulting solid was
washed with acetone and filtered to give 14‚2CH3SO3H as a
tan solid (0.11 g, 71%). Meth od B. To a stirred solution of 8
(0.50 g, 2.3 mmol) in 6 mL of DMSO at rt was added bromine
(120 µL, 2.3 mmol). After 1 h, the reaction mixture was diluted
with ether and decanted (3 × 75 mL). The resulting residue
was purified by flash chromatography (MeOH saturated with
NH3) to give 14 as a pale yellow solid. Addition of concentrated
HCl to a methanol solution of the free base and concentration
in vacuo afforded 14‚2HCl (0.36 g, 68%) as a colorless solid.
14‚2HCl: 1H NMR (DMSO-d6) δ 12.45 (br, 2H), 9.39 (br, 2H),
8.18 (bs, 3H), 5.98 (t, 1H, J ) 7.7), 2.97 (q, 2H, J ) 6.9), 2.67
(q, 2H, J ) 7.2); 1H NMR (D2O) δ 6.13 (t, 1H, J ) 7.9), 3.20 (t,
2H, J ) 7.1), 2.71 (dt, 2H, J ) 7.9 and 7.1); 13C NMR (D2O) δ
164.8 (s), 156.2 (s), 130.7 (s), 117.0 (d), 38.9 (t), 25.8 (t); IR
(KBr) 3100, 1690, 1540, 1310, 1250 cmj;1 UV λmax (MeOH) 226
and 271 nm; MS m/z (relative intensity) 155 (M+ + 1, 100),
138 (90). Anal. Calcd for C6H10N4O‚2HCl: C, 31.73; H, 5.33;
N, 24.67. Found: C, 31.79; H, 5.30; N, 24.59.
Cla th r od in (1c). To a stirred solution of 3‚2HCl (0.2 g,
0.95 mmol) in 2 mL of DMF at rt were added Na2CO3 (0.11 g,
1.0 mmol) and 2-(trichloroacetyl)pyrrole19 (0.25 g, 1.1 mmol).
The mixture was stirred for 1 h and then diluted with ether
and decanted (3 × 50 mL). The resulting residue was purified
by flash chromatography (CH2Cl2/MeOH saturated with NH3
17:3) to give 1c as the free base. Addition of concentrated HCl
to a methanol solution of the free base and concentration in
vacuo gave 1c‚HCl (0.19 g, 75%). 1c‚HCl: 1H NMR (DMSO-
d6) δ 12.39 (bs, 1H), 11.80 (bs, 1H), 11.49 (s, 1H), 8.33 (t, 1H,
J ) 5.9), 7.46 (s, 2H), 6.91 (s, 1H), 6.85 (m, 1H), 6.80 (m, 1H),
6.21 (d, 1H, J ) 16.2), 6.15 (dt, 1H, J ) 16.2, 4.9), 6.08 (m,
1H), 3.96 (t, 2H, J ) 4.9); IR (KBr) 1682, 1620, 1565, 1410,
1325; UV λmax (MeOH) 270 nm; MS m/z (relative intensity)
232 (M+ + 1, 100). HRMS calcd for C11H14N5O (MH+)
232.1199, found 232.1198.
Mon obr om od isp a ca m id e (2b). To a stirred solution of
14 (0.30 g, 1.9 mmol) in 5 mL of DMF under argon was added
4-bromo-2-(trichloroacetyl)pyrrole22 (0.67 g, 2.3 mmol) at rt.
After 72 h, the reaction mixture was diluted with ether and
decanted (2 × 100 mL). The resulting residue was purified
by flash chromatography (CH2Cl2/MeOH saturated with NH3
8:2) to give 2b as a white solid (0.53 g, 65%). 2b (free base):
1H NMR (CD3OD) δ 6.90 (d, 1H, J ) 1.5), 6.75 (d, 1H, J )
1.5), 5.73 (t, 1H, J ) 7.8), 3.43 (t, 2H, J ) 6.9), 2.49 (dt, 2H, J
1
J ) 7.4), 1.82 (p, 2H, J ) 7.3); H NMR (D2O) δ 6.54 (s, 1H),
3.01 (t, 2H, J ) 7.6), 2.61 (t, 2H, J ) 7.4), 1.94 (p, 2H, J )
7.6); 13C NMR (CD3OD) δ 148.7 (s), 127.2 (s), 110.4 (d), 39.9
(t), 27.1 (t), 22.5 (t); IR (KBr) 3310, 1667, 1473, 1140 cm-1
;
UV λmax (MeOH) 215 nm; MS m/z (relative intensity) 141 (M+
+ 1, 100), 124 (65). Anal. Calcd for C6H12N4‚2HCl: C, 33.82;
H, 6.62; N, 26.29. Found: C, 33.78; H, 6.59; N, 26.33.
tr a n s-2-Am in o-4,5-d im eth oxy-4-(3-a m in op r op yl)-2-im i-
d a zolin e (9). To a stirred solution of 8 (0.60 g, 2.8 mmol) in
10 mL of methanol at rt was added NCS (0.41 g, 3.1 mmol).
After 1 h, methanol was removed in vacuo without heat and
the resulting residue was washed with ether (3 × 100 mL)
and acetone (3 × 100 mL) to give 9 as an unstable colorless
oil (0.64 g, 83%): 1H NMR (DMSO-d6) δ 9.75 (bs, 1H), 9.70
(bs, 1H), 8.28 (bs, 2H), 8.14 (bs, 3H), 4.73 (s, 1H), 3.36 (s, 3H),
3.15 (s, 3H), 2.75 (q, 2H, J ) 5.7), 1.95-1.58 (m, 4H); 13C NMR
(DMSO-d6) δ 158.0 (s), 94.4 (s), 90.1 (d), 55.9 (q), 48.8 (q), 38.7
(t), 27.6 (t), 21.8 (t); IR (Nujol) 3136, 2855, 1692, 1570, 1184
cm-1; MS m/z (relative intensity) 203 (M+ + 1, 25), 171 (90).
HRMS calcd for C8H19N4O2 (MH+) 203.1509, found 203.1500.
6-Am in o-4a -(3-a m in op r op yl)-5H-im id a zo[4,5-b]-1,4-d i-
oxa n e (10). To a stirred solution of 8 (0.60 g, 2.8 mmol) in
10 mL of ethylene glycol at rt was added 1.1 equiv of NCS
(0.41 g, 3.1 mmol). After 20 h, the reaction mixture was
diluted with ether and decanted (3 × 100 mL). The resulting
residue was washed with acetone (3 × 100 mL) to give 10 as
an unstable colorless oil (0.61 g, 80%): 1H NMR (DMSO-d6) δ
9.40 (bs, 1H), 9.22 (bs, 1H), 8.42 (bs, 2H), 8.27 (bs, 3H), 5.18
(s, 1H), 3.76-3.62 (m, 4H), 2.78 (q, 2H, J ) 5.9), 1.82-1.69
(m, 4H); 13C NMR (DMSO-d6) δ 158.0 (s), 87.5 (s), 81.5 (d),
62.8 (t), 56.8 (t), 38.4 (t), 33.8 (t), 20.5 (t); IR (Nujol) 3404, 2740,
1695, 1571, 1272, cm-1; MS m/z (relative intensity) 201 (M+
+ 1, 100); HRMS calcd for C8H17N4O2 (MH+) 201.1353, found
201.1350.
2-Am in o-4-(3-a m in o-1-m et h oxyp r op yl)-1H -im id a zole
(11). A stirred solution of 9 (0.75 g, 2.7 mmol) was refluxed
in 10 mL of methanol for 2 d. The solvent was removed in
vacuo to afford a residue which consisted of starting material
9 and 11 as determined by NMR. Purification of the residue
by column chromatography (MeOH saturated with NH3) gave
11 (free base, 0.14 g, 30%) as a pale yellow oil: 1H NMR
(DMSO-d6 ) δ 6.35 (s, 1H), 5.11 (bs, 2H), 4.42 (br, 3H), 4.00 (t,
1H, J ) 6.6), 3.05 (s, 3H), 2.52 (t, 2H, J ) 6.7), 1.84-1.67 (m,
2H); 13C NMR (DMSO-d6) δ 149.9 (s), 131.8 (s), 113.9 (s), 74.3
(d), 54.8 (q), 38.6 (t), 38.5 (t); IR (KBr) 2944, 1584, 1489, 1344,
1193 cm-1; MS m/z (relative intensity) 171 (M+ + 1, 100);
HRMS, calcd for C7H15N4O (MH+) 171.1247, found 171.1250.
2-Am in o-4-(3-a m in o-1-(2-h yd r oxyet h oxy)p r op yl)-1H -
im id a zole (12). A solution of 10 (0.75 g, 2.7 mmol) was
refluxed in 10 mL of methanol for 2 d. The solvent was
removed in vacuo to afford a residue which consisted of a
mixture of starting material 10, along with 11 and 12, as
1
determined by H NMR. Purification of the residue by flash
chromatography (MeOH saturated with NH3) gave 11 (0.14
g, 30%) and 12 (0.081 g, 15%) as free bases, both of which were
pale yellow oils. 12: 1H NMR (DMSO-d6) δ 6.32 (s, 1H), 5.08
(bs, 2H), 4.40 (br, 4H), 4.18 (t, 1H, J ) 6.7), 3.42 (t, 2H, J )
5.1), 3.36-3.23 (m, 2H), 2.55 (t, 2H, J ) 6.6), 1.83-1.67 (m,
2H); 13C NMR (DMSO-d6) δ 150.0 (s), 132.9 (s), 113.7 (s), 73.4
(d), 69.4 (t), 60.7 (t), 38.4 (t), 37.8 (t); IR (KBr) 2812, 1693,
1560, 1166, 1010 cm-1; MS m/z (relative intensity) 201 (M+
+
1, 40), 139 (15), 97 (100); HRMS calcd for C8H17N4O2 (MH+)
201.1353, found 201.1351.
3-Am in o-1-(2-a m in oim id a zol-4-yl)p r op -1-en e (3) a n d
2-Am in o-5-(3-a m in op r op yl)-2-im id a zolin -4-on e (13).
A
solution of 9 (1.5 g, 5.5 mmol) in 10 mL of methanol was added
to 10 mL of m-xylene and heated at 135 °C for 3 h without a
condenser. During this time, the methanol evaporated. After
the solution was cooled to rt, the xylene was decanted and the

Synthesis of C11N5 Marine Alkaloids
J . Org. Chem., Vol. 63, No. 4, 1998 1253
) 7.8, 6.9); 13C NMR (CD3OD) δ 179.0 (s), 168.0 (s), 162.7 (s),
137.0 (s), 127.5 (s), 122.8 (d), 113.3 (d), 111.6 (d), 97.5 (s), 39.5
(t), 28.6 (t); IR (KBr) 3133, 2767, 1633, 1567, 1328 cm-1; UV
λmax (MeOH) 250 and 270(sh) nm; MS m/z (relative intensity)
326 (M+, 100). Anal. Calcd for C11H12BrN5O2: C, 40.51; H,
3.71; N, 21.47. Found: C, 40.49; H, 3.72; N, 21.40. 2b‚HCl:
1H NMR (CD3OD) δ 6.91 (d, 1H, J ) 1.5), 6.77 (d, 1H, J )
1.5), 6.16 (t, 1H, J ) 8.0), 3.48 (t, 2H, J ) 6.7), 2.6 (dt, 2H, J
) 8.0, 6.7); 13C NMR (CD3OD) δ 163.8 (s), 162.8 (s), 157.1 (s),
133.0 (s), 130.5 (s), 122.9 (d), 119.2 (d), 113.4 (d), 97.5 (s), 38.9
(t), 28.7 (t); UV λmax(MeOH) 232 and 272 nm. Anal. Calcd
for C11H12BrN5O2‚HCl: C, 36.44; H, 3.61; N, 19.31. Found:
C, 36.40; H, 3.68; N, 19.28.
Dih yd r oor oid in (15). To a stirred solution of 8 (free base,
0.66 g, 4.7 mmol) in 5 mL of DMF at rt was added 4,5-dibromo-
2-(trichloroacetyl)pyrrole24 (1.9 g, 5.2 mmol). The mixture was
stirred for 1 d and diluted with ether and decanted (3 × 75
mL). The resulting residue was purified by flash chromatog-
raphy (CH2Cl2/MeOH saturated with NH3 8:2) to afford 15 as
the free base. Addition of concentrated HCl to a methanol
solution of the free base and concentration in vacuo gave 15
as a white solid (1.3 g, 65%). 15: 1H NMR (DMSO-d6) δ 12.76
(s, 1H), 12.07 (s, 1H), 11.60 (s, 1H), 8.35 (t, 1H, J ) 5.7), 7.33
(s, 2H), 6.95 (d, 1H, J ) 2.7), 6.61 (s, 1H), 3.21 (q, 2H, J )
5.9), 2.44 (t, 2H, J ) 7.3), 1.77-1.70 (m, 2H); 13C NMR (D2O)
δ 162.0 (s), 147.2 (s), 127.7 (s), 127.3 (s), 114.3 (d), 109.5 (d),
106.5 (s), 99.8 (s), 39.5 (t), 27.9 (t), 22.5 (t); MS m/z (relative
intensity) 394 (M+ + 5, 50), 392 (M+ + 3, 100), 390 (M+ + 1,
50). Anal. Calcd for C11H13Br2N5O‚HCl: C, 30.90; H, 3.30;
N, 16.38. Found: C, 30.80; H, 3.48; N, 16.12.
tr a n s-4,5-Dih yd r o-4,5-d im eth oxyd ih yd r oor oid in (16).
To a stirred solution of dihydrooroidin hydrochloride (15) (0.40
g, 0.94 mmol) in 15 mL of methanol at -78 °C was added
t-BuOK (0.0734 g, 6.5 mmol) followed by bromine (53 µL, 1.0
mmol). After 10 min, the reaction mixture was quenched with
CH3SO3H (0.45 g, 4.7 mmol), warmed to rt, and filtered.
Concentration of the filtrate gave a residue that was purified
by flash chromatography (CH2Cl2/MeOH 8:2) to give 16 as a
yellow solid (0.37 g, 75%): 1H NMR (DMSO-d6) δ 12.67 (s, 1H),
9.42 (s, 1H), 9.36 (s, 1H), 8.20 (t, 1H, J ) 5.5), 8.13 (bs, 2H),
6.92 (s, 1H), 4.71 (s, 1H), 3.32 (s, 3H), 3.24-3.16 (m, 2H), 3.11
(s, 3H), 1.90-1.50 (m, 4H); 13C NMR (DMSO-d6) δ 158.8 (s),
157.6 (s), 128.2 (s), 112.4 (d), 104.4 (s), 97.7 (s), 94.7 (s), 90.1
(d), 55.8 (q), 48.9 (q), 38.4 (t), 27.7 (t), 23.9 (t); IR (KBr) 2941,
1693, 1567, 1416, 1241, cm-1 MS m/z (relative intensity) 454
(M+ + 5, 30), 454 (M+ + 3, 60), 454 (M+ + 1, 30), 422 (40), 390
(20), 307 (100), 289 (60). HRMS calcd for C13H20N5O3Br2 (MH+)
451.9928, found 451.9926.
Or oid in (1a ) a n d Dih yd r od isp a ca m id e (17). A solution
of 16 (0.30 g, 0.56 mmol) in 10 mL of methanol was added to
10 mL of m-xylene, and the whole was heated at 135 °C for 3
h without a condenser. During this time, the methanol
evaporated. After cooling, the xylene was decanted and the
residue washed with ether (3 × 100 mL) and acetone (2 × 100
mL). Purification of the resulting residue by flash chroma-
tography (CH2Cl2/MeOH saturated with NH3 8:2) gave oroidin
(1a ) (0.10 g, 48%) and dihydrodispacamide (17) (0.69 g, 30%).
Addition of concentrated HCl to a methanol solution of the
free base and concentration in vacuo gave 1a ‚HCl and 17‚-
HCl. 1a ‚HCl: 1H NMR (DMSO-d6) δ 12.78 (bs, 1H), 12.48
(bs, 1H), 11.85 (bs, 1H), 8.55 (t, 1H, J ) 4.9), 7.49 (bs, 2H),
6.99 (d, 1H, J ) 2.9), 6.91 (s, 1H), 6.21 (d, 1H, J ) 16.1), 6.13
(dt, 1H, J ) 16.1, 4.9), 3.95 (t, 2H, J ) 4.9); IR (KBr) 3290,
3160, 1685, 1564 cm-1; UV λmax (MeOH) 275 nm; MS m/z
(relative intensity) 394 (M+ + 5, 50), 392 (M+ + 3, 100), 390
(M+ + 1, 50). 17‚HCl: 1H NMR (DMSO-d6) δ 12.73 (bs, 1H),
12.28 (bs, 1H), 9.76 (bs, 1H), 9.03 (br, 1H), 8.87 (br, 1H), 8.29
(t, 1H, J ) 6.6), 6.93 (bs, 1H), 4.32 (t, 1H, J ) 6.1), 3.21 (q,
2H, J ) 6.6), 1.82-1.45 (m, 4H); MS m/z (relative intensity)
410 (M+ + 5, 50), 408 (M+ + 3, 100), 406 (M+ + 1, 50); HRMS
calcd for C11H14N5O2Br2 (MH+) 405.9513, found 405.9510.
Disp a ca m id e (2a ). Meth od A. To a stirred solution of
15 (0.10 g, 0.23 mmol) in 1 mL of DMSO at rt was added
bromine (13 µL, 0.23 mmol). After 1 h, the reaction mixture
was diluted with ether and decanted (3 × 50 mL). The
resulting residue was then purified by flash chromatography
(CH2Cl2:MeOH saturated with NH3 8:2) to give 2a as a white
solid (56 mg, 60%). Meth od B. To a stirred solution of 14
(0.32 g, 2.1 mmol) in DMF under argon at rt was added 4,5-
dibromo-2-(trichloroacetyl)pyrrole (0.93 g, 2.5 mmol). After 72
h, the reaction mixture was diluted with ether and decanted
(2 × 100 mL). The resulting residue was purified by flash
chromatography (CH2Cl2/MeOH saturated with NH3 8:2) to
give 2a as a white solid (0.69 g, 60%). 1H NMR (CD3OD) δ
6.78 (s, 1H), 5.72 (t, 1H, J ) 7.9), 3.42 (t, 2H, J ) 6.9), 2.50
(dt, 2H, J ) 7.9, 6.9); 13C NMR (CD3OD) δ 178.8 (s), 168.0 (s),
161.9 (s), 137.1 (s), 128.8 (s), 114.3 (d), 111.6 (d), 106.1 (s),
99.9 (s), 39.5 (t), 28.6 (t); UV λmax (MeOH) 250 and 274 nm;
MS m/z (relative intensity) 405 (M+, 100), 325 (30). Anal.
Calcd for C11H11Br2N5O2: C, 32.62; H, 2.74; N, 17.29. Found:
1
C, 32.57; H, 2.72; N, 17.30. 2a ‚HCl: mp >215 °C; H NMR
(CD3OD) δ 6.82 (s, 1H), 6.15 (t, 1H, J ) 8.0), 3.48 (t, 2H, J )
6.9), 2.62 (dt, 2H, J ) 8.0, 6.9); 13C NMR (CD3OD) δ 163.8 (s),
161.9 (s), 156.4 (s), 128.6 (s), 119.2 (d), 114.4 (d), 106.3 (s),
99.9 (s), 38.9 (t), 28.7 (t); IR (KBr) 3111, 2722, 1700, 1556, 1522
cm-1; UV λmax (MeOH) 224 and 278 nm. Anal. Calcd for
C
11H11Br2N5O2‚HCl: C, 29.92; H, 2.74; N, 15.86. Found: C,
29.88; H, 2.78; N, 15.78.
Ack n ow led gm en t. We thank Dr. J ohn Decatur for
his assistance in performing the NOESY experiment.
Financial support from the National Institutes of Health
(GM 50929), National Science Foundation (Young In-
vestigator Award to D.A.H.), American Chemical Society
Petroleum Research Fund, and Kanagawa Academy of
Science and Technology (KAST) is gratefully acknowl-
edged.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra for compounds 1a , 1c, and 2-17 (44 pages). This
material is contained in libraries on microfiche, immediately
follows this article in the microfilm version of the journal, and
can be ordered from the ACS; see any current masthead page
for ordering information.
(24) Bailey, D. M.; J ohnson, R. E. J . Med. Chem. 1973, 16, 1300.
J O9718298