Total synthesis of mololipids: A new series of anti-HIV moloka'iamine derivatives

Article abstract of DOI:10.1016/S0960-894X(00)00543-6

A new family of bioactive bromotyrosine derivatives, termed mololipids, was recently isolated from a Hawaiian sponge, but could not be resolved into individual components by chromatography. To complete their structural characterization and better understand structure-activity relationships, the first pure samples of dimyristoyl, distearoyl, dioleoyl, and stearoyl/oleoyl mololipids have now been prepared by total synthesis, and their anti-HIV activity investigated. (C) 2000 Published by Elsevier Science Ltd.

Full text of DOI:10.1016/S0960-894X(00)00543-6

Bioorganic & Medicinal Chemistry Letters 10 (2000) 2679±2681
Total Synthesis of Mololipids: A New Series of
Anti-HIV Moloka'iamine Derivatives
Ryan C. Schoenfeld,a Jean-Philip Lumb,a Jacques Fantinib and Bruce Ganema,*
aDepartment of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
b
 Â
Laboratoire de Biochimie et Biologie de la Nutrition, UPRESA-CNRS 6033, Faculte des Sciences de St. Jerome,
13397 Marseille, Cedex 20, France
Received 19 September 2000
AbstractÐA new family of bioactive bromotyrosine derivatives, termed mololipids, was recently isolated from a Hawaiian sponge,
but could not be resolved into individual components by chromatography. To complete their structural characterization and
better understand structure±activity relationships, the ®rst pure samples of dimyristoyl, distearoyl, dioleoyl, and stearoyl/oleoyl
mololipids have now been prepared by total synthesis, and their anti-HIV activity investigated. # 2000 Published by Elsevier
Science Ltd.
Natural products from marine organisms often possess
distinctive molecular frameworks and potentially useful
biological properties. Sponges of the order Verongida,
indigenous to Japanese and Hawaiian waters, are a
particularly rich source of unusual new structures.
Noteworthy among these is a series of bromotyrosine
derivatives (Fig. 1) that includes ceratinamine 1 and
moloka'iamine 2.1,2 Recently, a new series of lipophilic
bromotyrosine derivatives displaying anti-HIV activity
was isolated as a white waxy extract from a Verongid
sponge collected o€ Moloka'i, Hawaii. Named `mololi-
pids', the naturally-occurring mixture was assigned
general structure 3, consisting of bis-amides between 2
and long chain fatty acids.3 Here, we describe the ®rst
synthesis of pure samples of these structures, together
with their physical and biological properties.
Mass spectrometric analysis of the extract indicated that
the mololipids ranged in size from 750 to >1000 dal-
tons. However, repeated attempts at HPLC puri®cation
failed to separate the components of the mixture, thus
precluding the complete structural elucidation of indi-
vidual mololipids.3 One signi®cant unresolved question
concerned the constitution and point of attachment of
speci®c fatty acids. Although hydrolysis of the molo-
lipid mixture a€orded a series of linear and branched
fatty acids ranging in size from C14 to C20, it was not
possible to determine whether individual mololipids
Figure 1.
*Corresponding author. Tel.: +1-607-255-4174; fax: +1-607-255-6318; e-mail: bg18@cornell.edu
0960-894X/00/$ - see front matter # 2000 Published by Elsevier Science Ltd.
PII: S0960-894X(00)00543-6

2680
R.C. Schoenfeld et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2679±2681
Scheme 1.
Scheme 2.
carried identical or nonidentical fatty acid chains, or
whether certain fatty acids were uniquely or pre-
ferentially associated with either the aminoethyl or
aminopropyl side chains in 3.
resulting free amine group with oleoyl imidazole a€orded
unsymmetrically diacylated mololipid 9 in 94% yield.8
The mechanism by which mololipids exert their anti-
HIV-1 activity has not been elucidated. To shed light on
that question, a series of synthetic mololipids was
screened for gp120 binding by analyzing the interaction
of mololipid monolayers with recombinant gp120 at the
Having previously developed short synthetic routes to 1
and 2,4 we decided to address the remaining structural
questions surrounding the mololipids by synthesizing
pure samples of the assigned structures, which would
also make available larger quantities of these minor
(0.005% w/w) sponge constituents. The fact that molo-
lipids exhibit activity against HIV-1 without toxicity to
human lymphocytes3 provided an additional incentive
to couple the synthetic e€ort with structure±activity
studies on pure samples. Here we report the synthesis of
four representative mololipids by a route that permits
either direct bis-acylation of moloka'iamine 2 or step-
wise condensation of a suitably protected precursor
with di€erent fatty acyl groups.
air±water interface. Using
a previously described
assay9,10 that monitors the increase in surface pressure
ÁP, isotherms recording the variation of surface pres-
sure versus apparent molecular area at the air±water
interface indicated that each of the synthetic mololipids
formed monomolecular ®lms. Satisfactory compressi-
bility was observed at all ®lm pressures, and no dis-
continuities in the isotherms were detected, indicating
that the liquid expanded states of the monolayers were
well-behaved up to ®lm collapse. Recombinant gp120
(HIV-IIIB isolate) was then added to monolayers
prepared at an initial pressure of 8±10 mN/m.
Using standard procedures (acid chloride, pyridine or
Et3N, various solvents), attempts to bis-acylate
moloka'iamine 2 involved inhomogeneous reaction
conditions and led to complex product mixtures.
However, the corresponding myristoyl, stearoyl, and
oleoyl imidazoles reacted smoothly with 2 (THF,
50 ꢀC) to produce mololipids 4±6 in excellent yield
(Scheme 1).5
In the case of compounds 4, 5, 6, and 9, observed values
of ÁPmax were low (0, 3.8, 5.9, and 4.2 mN/m, respec-
tively) compared to galactosylceramide, a known ligand
for gp120.9 Our results indicated that none of the syn-
thetic mololipids interacted signi®cantly with gp120. It
thus seems unlikely that mololipids act by impairing
HIV±glycolipid interactions on the plasma cell mem-
brane. However, with an abundant synthetic supply of
representative mololipids in hand, it now becomes pos-
sible to test pure mololipids as inhibitors of other
enzymes involved in HIV-1 replication and infection.
Monoprotected diamine 7, a key intermediate in our
earlier synthesis of ceratinamine 1, was useful in devel-
oping a synthetic approach to mixed mololipids such as
9 (Scheme 2).
Acknowledgements
Acylation of 7 with stearoyl imidazole as earlier described
a€orded 8 (85%).6 Following removal of the acid-labile
2-(4-biphenylyl)-2-propyloxycarbonyl (Bpoc) protecting
group in dilute tri¯uoroacetic acid,7 reaction of the
Financial support from SIDACTION (grant to J.F.) is
gratefully acknowledged. R.C.S. is the recipient of a
Sokol Summer Fellowship. Support of the Cornell

R.C. Schoenfeld et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2679±2681
2681
NMR Facility has been provided by the National
Science Foundation (CHE 7904825, PGM 8018643) and
the National Institutes of Health (RR02002).
2H), 2.75 (t, 2H, J=6.9 Hz), 2.21±2.12 (m, 4H), 2.09±1.91 (m,
10H), 1.69±1.57 (m, 4H), 1.40±1.19 (m, 40H), 0.90±0.85 (m,
6H); 13C NMR (CDCl3, 75 MHz) d 173.2, 173.1, 151.4, 138.0,
132.9, 130.0, 129.9, 129.7, 118.1, 71.9, 40.3, 37.3, 36.9, 36.8,
34.5, 31.9, 29.7, 29.7, 29.6, 29.5, 29.3, 29.1, 27.2, 27.1,
25.8, 22.7, 14.1; IR (®lm) 3300, 2920, 2850, 1640, 1560,
1460 cm 1; ESI-MS m/z 880/882/884 (M+1).
References and Notes
6. For 8: mp 103±105 ꢀC; 1H NMR (CDCl3, 300 MHz) d 7.60±
7.55 (m, 4H), 7.45±7.40 (m, 4H), 7.36±7.32 (m, 3H), 6.09 (1H),
4.78 (1H), 4.06 (t, 2H, J=5.9 Hz), 3.61±3.55 (m, 2H), 3.35±
3.28 (m, 2H), 2.70 (t, 2H, J=6.4 Hz), 2.18 (t, 2H, J=7.5 Hz),
2.04 (tt, 2H, J=5.9, 6.4 Hz), 1.79 (s, 6H), 1.67±1.57 (m, 2H),
1.35±1.17 (m, 28H), 0.88 (t, 3H, J=6.5 Hz); 13C NMR
(CDCl3, 75 MHz) d 173.2, 155.0, 151.4, 145.3, 140.8, 139.8,
138.0, 133.0, 128.7, 127.2, 127.1, 124.7, 118.1, 80.8, 72.0, 41.6,
37.4, 37.0, 34.8, 31.9, 29.7, 29.5, 29.4, 29.3, 29.3, 29.2, 29.0,
25.8, 22.7, 14.1; IR (®lm) 3300, 2910, 2840, 1700, 1650, 1560,
1540, 1460, 1220 cm 1; ESI-MS m/z 873/875/877 (M+NH+4 ,
15%), 662/664/666 (100%).
1. Tsukamoto, S.; Kato, H.; Hiroka, H.; Fusetani, N. J. Org.
Chem. 1996, 61, 2936.
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Chem. 1993, 58, 6565.
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Tharnish, P.; Scheuer, P. J.; Hamann, M. T. J. Nat. Prod.
2000, 63, 501.
4. Schoenfeld, R. C.; Ganem, B. Tetrahedron Lett. 1998, 39,
4147.
5. (a) For 4: mp 130±131 ꢀC; H NMR (CDCl3, 300 MHz) d
1
7.34 (s, 2H), 6.08 (1H), 5.54 (1H), 4.07 (t, 2H, J=5.9 Hz),
3.61±3.55 (m, 2H), 3.49±3.43 (m, 2H), 2.75 (t, 2H, J=7.0 Hz),
2.21±2.12 (m, 4H), 2.05 (tt, 2H, J=5.9, 6.4 Hz), 1.68±1.56
(m, 4H), 1.25 (br. s, 40H), 0.90±0.85 (m, 6H); 13C NMR
(CDCl3, 75 MHz) d 173.3, 173.2, 151.4, 138.1, 133.0, 118.1,
72.0, 40.3, 37.3, 37.0, 36.8, 34.6, 31.9, 29.6, 29.5, 29.3, 29.3,
25.8, 22.7, 14.1; IR (®lm) 3300, 2920, 2840, 1640, 1550,
1470 cm 1; FABMS m/z 771/773/775 (M+1, 12%), 268
(100%). (b) For 5: mp 124±126 ꢀC; 1H NMR (CDCl3,
300 MHz) d 7.35 (s, 2H), 6.07 (1H), 5.52 (1H), 4.07 (t, 2H,
J=5.9 Hz), 3.61±3.55 (m, 2H), 3.49±3.43 (m, 2H), 2.75 (t, 2H,
J=7.0 Hz), 2.21±2.12 (m, 4H), 2.05 (tt, 2H, J=5.9, 6.4 Hz),
1.69±1.56 (m, 4H), 1.25 (br. s, 56H), 0.90±0.86 (m, 6H); 13C
NMR (CDCl3, 75 MHz) d 173.3, 173.2, 151.1, 138.0, 133.0,
118.2, 72.0, 40.4, 37.4, 37.0, 36.8, 34.6, 31.9, 29.7, 29.6, 29.5,
29.4, 29.3, 25.8, 25.8, 22.7, 14.1; IR (®lm) 3280, 2920, 2840,
1640, 1550, 1470 cm 1; FABMS m/z 883/885/887 (M+1,
12%), 329 (100%). (c) For 6: mp 97±99 ꢀC; 1H NMR (CDCl3,
300 MHz) d 7.34 (s, 2H), 6.09 (1H), 5.58 (1H), 5.41±5.26 (m,
4H), 4.07 (t, 2H, J=5.9 Hz), 3.60±3.54 (m, 2H), 3.49±3.42 (m,
7. (a) Sieber, P.; Iselin, B. Helv. Chim. Acta 1968, 51, 614. (b)
Schnabel, E.; Schmidt, G.; Klauke, E. Liebigs Ann. Chem.
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8. For 9: mp 102±104 ꢀC; H NMR (CDCl3, 300 MHz) d 7.35
1
(s, 2H), 6.07 (1H), 5.50 (1H), 5.40±5.26 (m, 2H), 4.07 (t, 2H,
J=5.9 Hz), 3.61±3.55 (m, 2H), 3.49±3.43 (m, 2H), 2.75 (t, 2H,
J=7.0 Hz), 2.21±2.12 (m, 4H), 2.09±1.93 (m, 6H), 1.70±1.56
(m, 4H), 1.39±1.17 (m, 48H), 0.90±0.85 (m, 6H); 13C NMR
(CDCl3, 75 MHz) d 173.2, 151.4, 138.0, 132.9, 130.0, 129.7,
118.1, 72.0, 40.3, 37.3, 37.0, 36.8, 34.6, 31.9, 29.8, 29.7, 29.5,
29.4, 29.3, 29.3, 29.1, 27.2, 27.1, 25.8, 25.7, 22.7, 14.1; IR (®lm)
3290, 2920, 2840, 1640, 1560, 1470 cm 1; ESI-MS m/z 882/
884/886 (M+1).
9. Hammache, D.; Pieroni, G.; Yahi, N.; Delezay, O.; Koch,
N.; Lafont, H.; Tamalet, C.; Fantini, J. J. Biol. Chem. 1998,
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10. The interaction between gp120 and the synthetic molo-
lipids was measured with the m-trough S tensiometer (Kibron
Inc., Helsinki, Finland) and the data were analyzed with the
FilmWare (version 2.3) software.