Stereochemical reassignment of heronamide A, a polyketide macrolactam from Streptomyces sp.

Article abstract of DOI:10.1016/j.tetlet.2013.01.012

The stereochemistry of heronamide A, a polyketide macrolactam from a marine-derived Streptomyces sp., was reassigned by detailed NMR analysis of the intact natural product and chemically modified derivatives.

Full text of DOI:10.1016/j.tetlet.2013.01.012

Tetrahedron Letters 54 (2013) 1531–1533
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Stereochemical reassignment of heronamide A, a polyketide macrolactam
from Streptomyces sp.
⇑
⇑
Ryosuke Sugiyama, Shinichi Nishimura , Hideaki Kakeya
Department of System Chemotherapy and Molecular Sciences, Division of Bioinformatics and Chemical Genomics, Graduate School of Pharmaceutical Sciences, Kyoto University,
Kyoto 606-8501, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The stereochemistry of heronamide A, a polyketide macrolactam from a marine-derived Streptomyces sp.,
was reassigned by detailed NMR analysis of the intact natural product and chemically modified
derivatives.
Received 16 November 2012
Revised 26 December 2012
Accepted 7 January 2013
Available online 12 January 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Heronamide
Streptomyces
Macrolactam
Stereochemistry
Polyene macrolactam is a unique class of microbial metabolites.
They exhibit a variety of biological activities, for example, antimi-
crobial and antitumor activity, modulation of Bcl-xL function, and
inhibition of leukocyte adhesion,1–6 and their modes of action are
of interest. However, in many cases their stereochemistry remains
to be determined partly due to their characteristic structural
features.4–10 For example, heronamide C (2)11 has three chiral cen-
ters; two oxymethine carbons C-8 and C-9 next to each other and
one isolated methine carbon C-19, which are connected through
triene and tetraene chains (Fig. 1). Many polyene macrolactam
compounds have similar structural features, making determination
of the relative stereochemistry difficult.3,4,6–9 Heronamide A (1) is a
putative biosynthetic product via heronamide C (2), originally
isolated from an Australian marine-derived Streptomyces sp.11
Heronamide A has a hexahydropyrrolizin-3-one unit (ring A and
B) and a cyclohexene ring (ring D), which are connected to form
another 10-membered ring system (ring C). Although its relative
stereochemistry was tentatively assigned by interpretation of the
NMR spectra and the absolute stereochemistry of C-17 was deter-
mined by the modified Mosher analysis,12 there was no direct evi-
dence to conclude the absolute stereochemistry of ring D. During
the course of our screening for novel secondary metabolites, we
isolated heronamide A from a Japanese marine-derived Streptomy-
ces sp. However, we found that the NMR data were not in agree-
ment with the proposed stereochemistry. We herein report the
reassignment of the absolute stereochemistry of heronamide A
(3), elucidated by careful interpretation of the NOESY data and
chemical modification. Our result indicates that the stereochemis-
try of other heronamide congeners should also be reinvestigated.
⇑
Figure 1. Chemical structures of heronamides. Heronamides A (1) and C (2) with
proposed stereochemistry and heronamide A (3) with reassigned absolute stereo-
chemistry are shown.
Corresponding authors. Tel.: +81 75 753 4524; fax: +81 75 753 4591.
E-mail addresses: nshin@pharm.kyoto-u.ac.jp (S. Nishimura), scseigyo-hisyo@
pharm.kyoto-u.ac.jp (H. Kakeya).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.01.012

1532
R. Sugiyama et al. / Tetrahedron Letters 54 (2013) 1531–1533
Table 1
NMR data for heronamide A in pyridine-d5
Position
dH (mult, J in Hz)a
NOESY
1
2
3
4
5
3.81 (ddd, 9.1, 7.1, 2.3)
5.81 (dd, 10.1, 7.1)
6.75 (ddd, 10.1, 10.1, 2.3)
5.60 (d, 10.1)
3, 5, 13, 15
2, 4, 16, 29
3, 28, 29
2, 7, 13
6
7
8
9
2.52 (dd, 11.3, 9.9)
4.14 (mb)
5, 13
12, 28
8, 10
4.61 (mc)
10
11
12
13
14
15
16
17
18a
18b
19
20a
20b
21
22
23
24
25
26
27
28
29
6.22 (ddd, 9.8, 5.1, 2.7)
5.94 (dd, 9.8, 1.7)
2.92 (mc)
9, 11
10, 12, 13
8, 11, 28, 29
2, 5, 7, 11, 15
5.01 (d, 10.9)
3.25 (dd, 9.1, 9.1)
4.30 (dd, 9.1, 6.9)
4.16 (mb)
2.59 (ddd, 12.8, 7.4, 7.4)
2.15 (ddd, 12.8, 8.0, 8.0)
4.20 (mb)
2.80 (ddd, 13.6, 7.4, 4.5)
2.66 (ddd, 13.6, 7.4, 7.4)
5.81 (ddd, 15.2, 7.4, 7.4)
6.27 (dd, 15.2, 10.4)
6.13 (dd, 15.2, 10.4)
5.63 (dt, 15.2, 7.4)
1.99 (dt, 7.4, 7.4)
1.34 (tq, 7.4, 7.4)
0.84 (t, 7.4)
2, 13, 17
3, 18b, 29
15, 18a
Figure 3.
esters of heronamide A.
D
d (=dS ꢀ dR, ppm) values for the bis-9,17-(S)- and bis-9,17-(R)-MTPA
17, 18b, 19,
16, 18a, 20b, 21
18a, 20a, 20b, 21
19, 20b, 21, 22
19, 20a, 21, 22
16, 18b, 19, 20a, 20b, 23
20a, 20b, 24
21, 25
22, 25
23, 24
24
25
matched those reported.14 However, the NOESY data (Table 1
and Fig. 2) did not agree with the stereochemistry proposed previ-
ously, for example, H-2, H-13, and H-15 mutually correlated, indi-
cating the cis orientation of H-2 and H-15 although the trans
orientation was proposed based on the large coupling constant
(3JH-2/H-15 = 9.2 Hz). We also observed a large coupling constant,
9.1 Hz (Table 1). To assign the relative stereochemistry, we care-
fully analyzed the NOESY spectrum. H-2 and H-7 were both corre-
lated to H-5 and H-13, whereas NOESY correlations between H-5
and H-13 were observed. In addition, H-2, H-13, and H-15 mutu-
ally correlated, suggesting that H-2, H-5, H-7, H-13, and H-15 are
placed on the same face of the 10-membered ring C (Fig. 2). NOESY
correlations from H3-29 to H-4, H3-28, H-12, and H-16, from H3-28
to H-4, H-8, and H-12, and between H-8 and H-12 placed all these
protons on the other face (Fig. 2). This interpretation was sup-
1.95 (s)
1.58 (s)
4, 8, 12, 29
3, 4, 12, 16, 28
a
b
c
500 MHz.
Signals overlapped.
Broad signals.
Heronamide A was obtained from the mycelium of Streptomyces
3
ported by two sets of large coupling constant values for JH-7/H-8
sp. NSU893, isolated from a sea sediment sample collected in Ura-
nouchi Bay, Kochi prefecture, Japan. Mycelium collected from a 5 L
culture was extracted with MeOH. The MeOH extract (3.0 g) was
concentrated and the residue was partitioned between 60% MeOH
and CHCl3. The CHCl3 layer (1.2 g) was fractionated by SiO2 column
chromatography (CHCl3/MeOH), followed by ODS flash column
chromatography (H2O/MeOH). Fractions containing heronamide
A (134 mg) were subjected to RP-HPLC (Cosmosil 5C8-MS) to give
11.6 mg of heronamide A. The physico-chemical properties includ-
ing IR, optical rotation, UV, and MS data were comparable to those
reported.13 The 1H and 13C chemical shifts in methanol-d4 also
3
and JH-7/H-12 (11.3 and 9.9 Hz),15 indicating the anti-orientation
of H-7 and H-8, and H-7 and H-12. Thus, the relative stereochem-
istry of heronamide A was revealed to be 2S⁄, 7S⁄, 8S⁄, 9R⁄, 12R⁄,
15S⁄, 16R⁄, 17S⁄, 19R⁄.16
To determine the absolute stereochemistry of heronamide A, we
applied the modified Mosher analysis.12 The previous report also
applied this method to heronamide A.11 However, the isopropyli-
dene derivative was converted to the MTPA esters and only 17-
OH was esterified. We reacted intact heronamide A with (R)- or
(S)-MTPACl to obtain 9,17-bis-(S)- or 9,17-bis-(R)-MTPA deriva-
tives, respectively (Fig. 3).17 Analysis of the differences between
Figure 2. Key NOESY correlations of heronamide A.

R. Sugiyama et al. / Tetrahedron Letters 54 (2013) 1531–1533
1533
the 1H NMR chemical shifts of these two MTPA derivatives con-
firmed the 17S stereochemistry while it revealed the 9R configura-
tion (Fig. 3), supporting our model led by the NMR analysis of the
intact compound (Fig. 2). We now conclude that the absolute ste-
reochemistry of heronamide A (3) was 2S, 7S, 8S, 9R, 12R, 15S, 16R,
17S, 19R (Fig. 1).
In summary, we isolated heronamide A from a Japanese
marine-derived Streptomyces sp. NSU893 and reassigned the
stereochemistry. Our assignment differed from the previously
proposed structure in two points; H-2 and H-15 were placed in a
cis configuration and ring D had opposite stereochemistry. We
assigned the relative stereochemistry by precise interpretation of
the NOESY data, while the absolute stereochemistry was unambig-
uously determined by the modified Mosher analysis. Since herona-
mides B and C possess the same diol function, we suggest that their
stereochemistry should also be reinvestigated.
2. Futamura, Y.; Sawa, R.; Umezawa, Y.; Igarashi, M.; Nakamura, H.; Hasegawa, K.;
Yamasaki, M.; Tashiro, E.; Takahashi, Y.; Akamatsu, Y.; Imoto, M. J. Am. Chem.
Soc. 2008, 130, 1822.
3. Müller, H.; Bischoff, E.; Fiedler, V. B.; Weber, K.; Fugmann, B.; Rosen, B.
Germany Patent 4,231,289, 1994.
4. Kojiri, K.; Nakajima, S.; Suzuki, H.; Kondo, H.; Suda, H. J. Antibiot. 1992, 45, 868.
5. Jørgensen, H.; Degnes, K. F.; Sletta, H.; Fjærvik, E.; Dikiy, A.; Herfindal, L.;
Bruheim, P.; Klinkenberg, G.; Bredholt, H.; Nygard, G.; Doskeland, S. O.;
Ellingsen, T. E.; Zotchev, S. B. Chem. Biol. 2009, 16, 1109.
6. Takahashi, I.; Oda, Y.; Nishiie, Y.; Ochiai, K.; Mizukami, T. J. Antibiot. 1997, 50,
186.
7. Mitchell, S. S.; Nicholson, B.; Teisan, S.; Lam, K. S.; Potts, B. C. M. J. Nat. Prod.
2004, 67, 1400.
8. Udwary, D. W.; Zeigler, L.; Asolkar, R. N.; Singan, V.; Lapidus, A.; Fenical, W.;
Jensen, P. R.; Moore, B. S. Proc. Natl. Acad. Sci. U.S.A. 2007, 104, 10376.
9. Jørgensen, H.; Degnes, K. F.; Dikiy, A.; Fjærvik, E.; Klinkenberg, G.; Zotchev, S. B.
Appl. Environ. Microbiol. 2010, 76, 283.
10. Yang, S.-X.; Gao, J.-M.; Zhang, A.-L.; Laatsch, H. Bioorg. Med. Chem. Lett. 2011,
21, 3905.
11. Raju, R.; Piggott, A. M.; Coute, M. M.; Capon, R. J. Org. Biomol. Chem. 2010, 8,
4682.
12. Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J. Am. Chem. Soc. 1991, 113,
4092.
Acknowledgments
13. Yellow oil; IR (neat) kmax 3360 (br), 2926 (m), 2360 (m), 1666 (brs) cm-1; ½a D20
ꢁ
ꢀ42 (c 0.10 in MeOH); UV (MeOH) kmax (log
e) 224 nm (4.44); HR MS (ESI) m/z
466.2948 [M+H]+ calcd for C29H40NO4, 466.2952.
We thank Drs. S. Sato and M. Katayama (Nippon Suisan Kaisha
Ltd, Japan) for their support in isolation and culture of the produc-
ing strain of heronamide A. This work was supported in part by re-
search grants from Japan Society for the Promotion of Science, the
Ministry of Education, Culture, Sports, Science and Technology of
Japan, and Suntory Institute for Bioorganic Research.
14. The 1H NMR signals of heronamide A in pyridine-d5 dispersed well while many
signals overlapped in methanol-d4. Hence we analyzed the NOESY data in
pyridine-d5.
15. Two coupling constant values were deduced by interpretation of the peak
shape of H-7. However, we could not determine which value is for 3JH-7/H-8 (or
3JH-7/H-12) since the 1H NMR peaks corresponding to H-8 and H-12 were broad.
3
In methanol-d4, a large coupling constant value for JH-7/H-8 (11.9 Hz) was
observed, confirming their anti-orientation.
16. Two hydroxyl groups at C-8 and C-9 were placed in a cis relationship by
analyzing the NOESY data of an isopropylidene derivative as reported
Supplementary data
previously. In addition, NOESY correlations around rings
A and B were
comparable to those reported. Our data also assigned the relative
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.
01.012.
configurations as 15S⁄, 16R⁄, 17S⁄, 19R⁄.
17. A solution of heronamide A (1.0 mg, 2.1
lmol), (S)-MTPACl (5.0 mg, 20
lmol),
and DMAP (1.6 mg, 13 mol) in pyridine/CH2Cl2 (100/400
l
l
L) was stirred at
room temperature for 12 h. The reaction was quenched with satd aq NaHCO3
and extracted with EtOAc. The organic layer was dried over Na2SO4 and
fractionated by ODS flash column chromatography, followed by HPLC
References and notes
(Cosmosil 5C8-MS) to yield the 9,17-bis-(R)-MTPA ester (0.1 mg, 0.11
as a white powder. The 9,17-bis-(S)-MTPA ester was prepared in the same way.
lmol)
1. Shindo, K.; Kamishohara, M.; Odagawa, A.; Matsuoka, M.; Kawai, H. J. Antibiot.
1993, 46, 1076.