Stereospecific synthesis of 23-hydroxyundecylprodiginines and analogues and conversion to antimalarial premarineosins via a Rieske oxygenase catalyzed bicyclization

Article

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Stereospeciﬁc Synthesis of 23-Hydroxyundecylprodiginines and

Analogues and Conversion to Antimalarial Premarineosins via a

Rieske Oxygenase Catalyzed Bicyclization

Papireddy Kancharla,^†,‡Wanli Lu,^†,‡Shaimaa M. Salem,^†Jane Xu Kelly,^†,§and Kevin A. Reynolds*^,†

^†Department of Chemistry, Portland State University, Portland, Oregon 97201, United States

^§Department of Veterans Aﬀairs Medical Center, Portland, Oregon 97239, United States

S

* Supporting Information

ABSTRACT: Facile and highly eﬃcient synthetic routes for the synthesis of (S)- and (R)-23-hydroxyundecylprodiginines

((23S)-2, and (23R)-2), 23-ketoundecylprodiginine (3), and deuterium-labeled 23-hydroxyundecylprodiginine ([23-d]-2) have

been developed. We demonstrated a novel Rieske oxygenase MarG catalyzed stereoselective bicyclization of (23S)-2 to

premarineosin A (4), a key step in the tailoring process of the biosynthesis of marineosins, using a marG heterologous expression

system. The synthesis of various A−C-ring functionalized prodiginines 32−41 was achieved to investigate the substrate

promiscuity of MarG. The two analogues 32 and 33 exhibit antimalarial and cytotoxic activities stronger than those of the

marineosin intermediate 2, against Plasmodium falciparum strains (CQ^S-D6, CQ^R-Dd2, and 7G8) and hepatocellular HepG2

cancer cell line, respectively. Feeding of 34−36 to Streptomyces venezuelae expressing marG led to production of novel

premarineosins, paving a way for the production of marineosin analogues via a combinatorial synthetic/biosynthetic approach.

This study presents the ﬁrst example of oxidative bicyclization mediated by a Rieske oxygenase.

the synthesis of various 2,2′-bipyrrole-5-carboxaldehydes¹²and

INTRODUCTION

■

have subsequently generated a library of middle ring (ring B)

Prodiginines (1−3, Figure 1) are a family of red-pigmented

natural products characterized by a 4-methoxy bipyrrole moiety

functionalized prodiginines and tambjamines for their anti-

malarial activity and structure−activity relationship (SAR)

studies.

linked to a variety of alkyl-substituted pyrroles.¹These

compounds have been extensively studied for their intriguing

biological activities (antimicrobial,²immunosuppressive,³anti-

tumor,^2a,b,4anticancer,⁵and antimalarial^6,7) and modes of

action (transmembrane anion transport^5c−e,8and DNA

intercalation⁹). Some of these compounds have shown clinical

potential, and the synthetic prodiginine analogue obatoclax-3

(GX15-070) has completed phase II clinical trials for the

treatment of small cell lung cancer and is engaged in multiple

clinical trials for the treatment of other cancer conditions.^10,11

As a part of our ongoing interest in developing new

antiparasitic agents, we recently reported the antimalarial

activity of natural and synthetic prodiginines.⁷This work

showed that the terminal nonalkylated pyrrole (ring A) and 3,5-

dialkyl substitutions on the other terminal pyrrole (ring C) of

natural prodiginines are crucial for potent antimalarial activity.

In addition, we had demonstrated in mice that prodiginines can

be administered orally with marked parasite clearance,

including cures in some cases, without evident weight loss

and toxicity. Recently we also have developed new methods for

In 2008, Fencial and co-workers isolated marineosin A (6)

and B (7) (Figure 1), a new class of modiﬁed prodiginines with

an unusual spiro-tetrahydropyran-aminal and pyrrole-macro-

cyclic rings from the marine Streptomyces sp. CNQ-617.¹³

Marineosins were shown to have strong and selective

anticancer activity, as well as antimalarial activity.^13,14The

intriguing structure and biological activities of marineosins has

spurred eﬀorts toward total synthesis attempts. In recent years,

several research groups have attempted to accomplish the total

synthesis but were successful only in the synthesis of key

fragments.¹⁵To date, the total synthesis of marineosins is still

incomplete.

Recently we have demonstrated the ﬁnal steps of the

marineosin biosynthetic pathway through identiﬁcation and

characterization of the corresponding mar gene cluster from

Received: October 14, 2014

Published: November 7, 2014

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Figure 1. Marineosin biosynthetic pathway.

marine Streptomyces sp. CNQ-617 (Figure 1).¹⁴Expression of

the entire gene cluster in a S. venezuelae host led to production

of marineosins, whereas gene replacement of marG, which

encodes a Rieske nonheme iron-dependent oxygenase, led to

accumulation of 23-hydroxyundecylprodiginine (2) and 23-

ketoundecylprodiginine (3). Replacement of marA, encoding a

putative dehydrogenase, led to accumulation of premarineosin

A (4) and 16-ketopremarineosin A (5) (Figure 1). These

observations did not support either previous marineosin

biosynthetic hypotheses, in which the pathway either passes

through an enone analogue of undecylprodiginine¹³or involves

a hydroxylation of undecylprodiginine by a RedG homologue

(MarG).^15aRather, they suggested a pathway which culminates

in a MarG-catalyzed cyclization of either 2 or 3 to form

premarineosin A, which is subsequently reduced by MarA to

generate marineosins (Figure 1).

In the well-established prodiginine biosynthetic pathway, it

has been shown that RedH condenses an 2-undecylpyrrole and

a 4-methoxy-2,2′-bipyrrolyl-5-carboxaldehyde (MBC, 8) to

generate undecylprodiginine (1), which is then cyclized by

the Rieske oxygenase RedG to form streptorubin B (Figure

2).^16,17An elegant study on the biosynthesis of metacyclopro-

diginine by the same group demonstrated an analogous

oxidative cyclization catalyzed by another RedG homologue,

McpG.¹⁷These two Rieske oxygenases, RedG and McpG,

catalyze the regio- and stereoselective cyclization of the same

substrate, undecylprodiginine (1), to form 10- and 12-

membered macrocyclic rings, respectively.¹⁷More interestingly,

the absolute stereochemistry of streptorubin B and metacyclo-

prodiginine is varying at C-20 and C-22, respectively, showing

that the oxidative cyclization is stereospeciﬁc (Figure 2).^17,18

The product of the marH gene shares 80% similarity with

RedH, while the novel Rieske oxygenase MarG shares 80%

similarity with RedG and 70% similarity with McpG (Figure 2).

It seems plausible that the putative marineosin biosynthetic

intermediate (S)-23-hydroxyundecylprodiginine ((23S)-2)

might be produced via a MarH condensation of 8 and

(10′S)-hydroxyundecylpyrrole ((10′S)-9). Subsequently, the

unique bicyclization, including C−C bond formation, and the

intramolecular hydroalkoxylation are catalyzed by MarG to

generate premarineosins (Figure 2).

The proposed ﬁnal steps of marineosin biosynthesis provide

an inspiration for a new approach for the elusive synthesis of

marineosins. To that end, the proposed marineosin biosyn-

thetic pathway intermediates 8 and (10′S)-9 would be

synthesized and then condensed to form (23S)-2. MarG

would then provide enzymatic access to premarineosin A (4),

and thus marineosins (6 and 7), after a ﬁnal chemical reduction

step. In this work we report the successful synthesis of (S)- and

(R)-23-hydroxyundecylprodiginines ((23S)-2 and (23R)-2),

23-ketoundecylprodiginine (3), and deuterium-labeled 23-

hydroxyundecylprodiginine ([23-d]-2). In vivo feeding experi-

ments using a marG heterologous expression system unequiv-

ocally demonstrated the role played by MarG to catalyze

stereoselective bicyclization of (23S)-2 to premarineosin A (4).

In addition, we also report the elucidation of the substrate

promiscuity of MarG using a series of chemically synthesized

new analogues of 2. Finally, we report on the potent

antimalarial activity of two derivatives of 2, 23-alkoxyundecyl-

prodiginines 32 and 33.

RESULTS AND DISCUSSION

■

Synthesis of (S)- and (R)-23-Hydroxyundecylprodigi-

nines (23S)-2 and (23R)-2. Our initial eﬀorts focused on the

synthesis of the proposed biosynthetic intermediates 8, (10′S)-

9, and (10′R)-9 from the key precursors 10−13 (Scheme 1).

By use of literature methodologies, 4-methoxy-2,2′-bipyrrole-5-

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Figure 2. Roles of Rieske oxygenases RedG, McpG, and MarG, along with other tailoring enzymes, in the biosynthesis of the prodiginine natural

products streptorubin B, metacycloprodiginine and marineosin: (A) late stages of the biosynthetic pathways leading to streptorubin B,

metacycloprodiginine, and marineosins; (B) biosynthetic gene cluster of marineosins and the putative tailoring genes, with the Rieske oxygenase

genes redG, mcpG, and marG highlighted in red, genes involved in undecylprodiginine analogue formation highlighted in blue, and the gene encoding

premarineosin reductase highlighted in green; (C) multiple amino acid alignment of RedG, McpG, and MarG, with conserved sequences within

CXH, CXXH motifs that ligate to the [2Fe-2S] cluster (Rieske center) marked with red asterisks and conserved sequences in the EXXHX₄H motif

that binds to ferrous ion (nonheme iron center) marked with black asterisks.

carboxaldehyde (MBC, 8) was prepared from the commercially

available 4-methoxy-3-pyrrolin-2-one (10) in two steps.¹⁹

The synthesis of (10′S)-hydroxyundecylpyrrole ((10′S)-9)

and (10′R)-hydroxyundecylpyrrole ((10′R)-9) is outlined in

Schemes 2 and 3. 1-(Phenylsulfonyl)-pyrrole (14) was treated

with dichloromethyl methyl ether to give 1-(phenylsulfonyl)-2-

pyrrolecarboxaldehyde (15) in 82% yield,²⁰which was further

treated with 3-butenylmagnesium bromide in THF at 0 °C to

give compound 16 in 85% yield. To avoid a two-step sequence

(oxidation of alcohol group, and deoxygenation, and depro-

tection by NaBH₄/reﬂux)^15b,cfor the conversion of compound

16 to 2-(4-pentenyl)pyrrole (11), we successfully developed a

one-pot cascade reaction by using LiAlH₄in THF at 0 °C to

reﬂux conditions (see the Experimental Section), and this

proceeded with excellent yields (Scheme 2). Conversely, (S)-

propylene oxide (17) was treated with 4-pentenylmagnesium

bromide (18) in the presence of CuI to give the (S)-2-hydroxy-

7-octene (12) in 92% yield.²¹Subsequently, a standard cross-

metathesis reaction between 11 and 12 by Grubbs II catalyst

and further hydrogenation of the oleﬁn bond of 19 with Pd/C

(10%) under H₂gas at room temperature led to the desired

compound (10′S)-9 (Scheme 2). We employed a similar

reaction sequence to furnish the anti isomer (10′R)-9 from (R)-

propylene oxide (20) via the appropriate intermediates (R)-2-

hydroxy-7-octene (13), 11, and 21 as outlined in Scheme 3.

With the proposed biosynthetic intermediates (10′S)-9 and

(10′R)-9 in hand, we then sought and successfully synthesized

the desired (S)-23-hydroxyundecylprodiginine ((23S)-2) and

(R)-23-hydroxyundecylprodiginine ((23R)-2) using an acid-

mediated (methanolic HCl) condensation with 4-methoxy-2,2′-

bipyrrole-5-carboxaldehyde (8) in good yields as outlined in

Scheme 4.⁷Compounds (23S)-2 and (23R)-2 were fully

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Stereochemical Analysis and Conversion of (23S)-2

and (23R)-2 to Premarineosin A (4) by a MarG-Catalyzed

Bicyclization. Sequence analysis suggests that MarG is a

Rieske nonheme iron-dependent oxygenase, containing the

universally conserved N-terminal CXH and CXXH motifs that

ligate to the [2Fe-2S] cluster in the Rieske center and

conserved EXXHX₄H motif that binds to ferrous ion in the

nonheme iron center. It was initially proposed that MarG is

involved in the hydroxylation and subsequent spiroaminal ring

formation of marineosin from an undecylprodiginine inter-

mediate.^15aOur previous work suggests that MarG is not

responsible for hydroxylation but catalyzes spiroaminal

formation from an isomer of 2 (Figure 1).¹⁴Taking into

consideration the diﬃculties associated with in vitro protein

reconstitution of this class of enzymes, we sought the

overexpression of MarG in S. venezuelae ATCC 15439 (S.

venezuelae MarG, see the Experimental Section and Tables S1

and S2 (Supporting Information)) in order to study its role in

the biosynthesis of marineosin in vivo. Feeding of synthesized

(23S)-2 to S. venezuelae MarG resulted in the production of

both premarineosin A (4) and 16-ketopremarineosin A (5, a

presumptive shunt product) (Scheme 5). The production of 4

Scheme 1. Retrosynthesis of (S)- and (R)-23-(Hydroxy/

keto)undecylprodiginines (23S)-2, (23R)-2, and 3

Scheme 2. Synthesis of (10′S)-Hydroxyundecylpyrrole

((10′S)-9)

Scheme 5. Conversion of (23S)-2, (23R)-2, 3, and [23-d]-2

to Premarineosins by MarG

Scheme 3. Synthesis of (10′R)-Hydroxyundecylpyrrole

((10′R)-9)

and 5 was conﬁrmed by LC-MS analysis using side by side

comparison with standard premarineosins (Figure 3 and Figure

S2 (Supporting Information)). Surprisingly, feeding of the

opposite isomer, (23R)-2, to S. venezuelae MarG also provided

both premarineosin A (4) and 16-ketopremarineosin A (5), as

shown in Scheme 5 (Figure 3 and Figure S2). Unfortunately,

the conversion of prodiginines to premarineosins was very

poor, and the resulting products were not isolated. However,

they were conﬁrmed by LC-MS analysis using side by side

comparison with standard premarineosins. The conversion of

both isomers (23S)-2 and (23R)-2 into premarinesosin A,

which has the S stereocenter at C-23, by the S. venezuelae MarG

strain presented an enigma. The diastereomer of 4,

premarineosin B,¹⁴was not observed in detectable levels. As

premarineosins A and B diﬀer only in the stereochemistry at

the spiroaminal carbon (C-8), it is most likely that

premarineosin B arises from an inversion of the aminal

nitrogen of 4. The absence of detectable levels of premarineosin

B indicates that premarineosin A (4) is more thermodynami-

Scheme 4. Synthesis of (S)- and (R)-23-

Hydroxyundecylprodiginines ((23S)-2 and (23R)-2)

characterized by NMR and MS analysis and compared with the

TLC and HPLC proﬁles of natural product 2 (Figure S1,

Supporting Information).

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Scheme 6. Synthesis of 23-Ketoundecylprodiginine (3)

previously reported by using Dess−Martin periodinane,²²but

to our knowledge, Ley−Griﬃth oxidation conditions (TPAP/

NMO) have never been exploited to unprotected pyrroles. To

demonstrate the generality of this controlled oxidation, the

reaction was carried out under the same reaction conditions on

2-ethylpyrrole (24a), 2,4-dimethylpyrrole (24b), and 3-ethyl-

2,4-dimethylpyrrole (24c) and successfully led to the desired 5-

alkylene-1,5-dihydropyrrol-2-ones 25a−c (Table 1). Con-

versely, the same reaction conditions with N-protected 2-

ethylpyrroles 24d−f failed to provide the corresponding

oxidative products in detectable levels. The N-methylpyrrole

24g was completely converted into the corresponding oxidized

product 25d in excellent yield (Table 1).

Figure 3. LC-MS (EIC) proﬁles of feeding (23S)-2 and (23R)-2 to S.

venezuelae MarG: (A) EIC for m/z 408.26−408.27, corresponding to

[M + H]⁺for 4, from an LC-MS analysis of standard 4; (B) EIC for

m/z 410.28−410.29, corresponding to [M + H]⁺for (23S)-2, from an

LC-MS analysis of synthesized (23S)-2; (C) EIC for m/z 408.26−

408.27, corresponding to [M + H]⁺for 4, from an LC-MS analysis of

extracts of S. venezuelae MarG fed with (23S)-2; (D) EIC for m/z

408.26−408.27, corresponding to [M + H]⁺for 3, from an LC-MS

analysis of synthesized 3; (E) EIC for m/z 408.26−408.27,

corresponding to [M + H]⁺for 4 and [M + H]⁺for 3, from an LC-

MS analysis of extracts of S. venezuelae MarG fed with (23R)-2.

cally stable under pathway conditions. It is noteworthy that

feeding (23R)-2 to S. venezuelae MarG resulted in the

production of 23-ketoundecylprodiginine (3) as detected by

LC-MS analysis (Figure 3). Intriguingly, 3 was not observed

when the experiment was carried out with (23S)-2 (Figure 3).

The production of 3 suggests that (23R)-2 is initially converted

into 3, and the latter may also be participating in the MarG-

catalyzed cyclization to provide premarineosins. To test this

hypothesis and determine the actual intermediate for MarG, we

sought the synthesis of 3.

Table 1. Synthesis of 5-Alkylene-1,5-dihydropyrrol-2-ones

(25a−c) and 25d

Synthesis of 23-Ketoundecylprodiginine (3) and

Subsequent Conversion to Premarineosins. We antici-

pated that the prodiginine 3 could be obtained directly from

(23S)-2 and/or (23R)-2 by an oxidation of the hydroxyl group

at C-23, as shown in Scheme 6. Unfortunately, we were unable

to convert compound (23S)-2 and/or (23R)-2 to the desired

product 3 under a variety of oxidation reagents/conditions,

which resulted in either formation of several products or

extensive decomposition. We therefore took an alternative

route that exclusively leads to the ﬁnal product 3 (Scheme 6).

To achieve this, we took either the (10′S)-9 and/or (10′R)-9 as

a starting material and subjected them to several oxidizing

agents. A Ley−Griﬃth oxidation provided the desired 10′-

ketoundecylpyrrole (22) in 51% isolated yield (Scheme 6). It is

noteworthy that the Ley−Griﬃth oxidation of (10′S)-9 and/or

(10′R)-9 also provided the 1,5-dihydropyrrol-2-one 23 as a side

product in considerable amount (15% isolated yield). The

individual compound 23 was fully characterized by extensive

NMR and MS analysis (Supporting Information). This kind of

controlled oxidation of N-protected pyrroles has been

a

nr = no reaction.

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These 5-alkylene-1,5-dihydropyrrol-2-ones 23 and 25a−c are

highly functionalized and therefore are excellent building blocks

for the synthesis of natural and synthetic products of biological

importance: for example, pulchellalactam is a potent CD45

protein tyrosine phosphatase (PTP) inhibitor, which was

isolated from the marine fungus Corollospora pulchella.²³

Finally, the acid-catalyzed condensation of the key intermediate

22 with 8 provided the desired 23-ketoundecylprodiginine (3)

in 50% isolated yield (Scheme 6), and it was fully characterized

by NMR and MS analysis and compared with the TLC and

HPLC proﬁles of natural product 3 (Figure S1, Supporting

Information).

Cyclization. Adopting an approach developed by Li and

Herzon in our syntheses,²⁴10-undecynoic acid (26) was

treated with Au(IPr)Cl (0.02 equiv), AgO₂CCF₃(0.02 equiv),

and Shvo’s catalyst (0.02 equiv) in a mixture of water and

isopropyl alcohol (14% v/v), to give the desired 10-

hydroxyundecanoic acid (27) in 82% yield (Scheme 7). 10-

Oxoundecanoic acid (28) was synthesized by oxidation of the

hydroxyl group of 27 using Dess−Martin periodinane

conditions, which upon treatment with sodium borodeuteride

(NaBD₄) gave the [10-d]-10-hydroxyundecanoic acid ([10-d]-

27). Attempts to convert the acid group of [10-d]-27 to acid

chloride using either oxalyl chloride (COCl)₂or thionyl

chloride (SOCl₂) in dichloromethane/toluene, with a sub-

sequent Friedel−Crafts acylation on pyrrole in the presence of

Zn/toluene²⁵led to the formation of several products.

Therefore, the hydroxyl group at C-10 needed to be protected.

The eﬃciency of this reaction sequence (formation of acid

chloride and Friedel−Crafts acylation of pyrrole) toward the 2-

acylpyrrole [10′-d]-30 was improved by the protection of the

hydroxyl group (C10−OH) of [10-d]-27 with Ac₂O/pyridine.

The reaction of [10-d]-10-acetoxyundecanoic acid ([10-d]-29)

with SOCl₂/DMF (catalytic)/toluene with a subsequent

acylation of pyrrole in the presence of Zn/toluene provided

the desired 2-acylpyrrole [10′-d]-30 as a major product along

with the 3-acylpyrrole [10′-d]-31 as a minor product. This ratio

of products is in contrast with the standard regioselective

acylation method, in which 2-acylpyrrole is the single product

from pyrrole and acid chloride.²⁵The two isomers [10′-d]-30

(57%) and [10′-d]-31 (8%) were isolated by silica gel column

chromatography and characterized by NMR and MS analysis.

Then the 2-acylpyrrole [10′-d]-30 was smoothly converted to

[10′-d]-9 in 67% isolated yield by using an excess (12 equiv) of

NaBH₄in isopropyl alcohol (IPA) under reﬂux (Scheme 7).^7,26

The acid-catalyzed condensation of [10′-d]-9 with 8 provided

the desired racemic [23-d]-23-hydroxyundecylprodiginine ([23-

d]-2) in 70% isolated yield (Scheme 7).

Feeding of 23-ketoundecylprodiginine (3) to the S.

venezuelae MarG expression strain clearly provided both

premarineosin A (4) and 16-ketopremarineosin A (5), as

shown in Scheme 5 (Figure 4 and Figures S2 and S3

Feeding of ∼90% deuterium-labeled racemic compound [23-

d]-2 to the S. venezuelae MarG expression host led to

production of [23-d]-4 and 4 in ∼1.2:1 ratio, along with the

shunt products [23-d]-5 and 5, as shown in Scheme 5 (Figure 4

and Figures S2−S4 (Supporting Information)). Production of

deuterium-labeled premarineosin A ([23-d]-4) is consistent

with a pathway that directly proceeds from the isomer [23S-23-

d]-2 without oxidation to 3 (Scheme 5). The detection of

∼45% unlabeled product premarineosin A (4) via MS analysis

(Figure S4) from ∼90% labeled [23-d]-2 is consistent with a

pathway in which the hydroxyl group at C-23 of [23R-23-d]-2

is oxidized to 3 (as observed with (23R)-2 feeding experiment),

the deuterium label is lost, and then the compound is reduced

to the unlabeled (23S)-2, which is then converted by MarG to

premarineosin A (4) (Scheme 5). Our ﬁndings are thus all

consistent with a role of MarG in catalyzing formation of

premarineosins exclusively from (S)-23-hydroxyundecylprodi-

ginine ((23S)-2).

Synthesis of Hydroxyundecylprodiginine Analogues

To Probe MarG Substrate Promiscuity. Having determined

the intermediates involved in the biosynthesis of marineosin

and the role of MarG, we wanted to study the potential of

MarG-generated marineosin analogues. Using the general

approach for synthesis of (23S)-2, (23R)-2, 3, and [23-d]-2

and various 2,2′-bipyrrole-5-carboxaldehydes (52a−d),^7,12we

synthesized various A- and B-ring functionalized (hydroxy/

alkoxy)undecylprodiginines 2 and 32−41, as shown in Schemes

Figure 4. LC-MS (EIC) proﬁles of 4 and [23-d]-4 from feeding of 3

and [23-d]-2 to S. venezuelae MarG: (A) EIC for m/z 408.26−408.27,

corresponding to [M + H]⁺for 4, from an LC-MS analysis of standard

4; (B) EIC for m/z 408.26−408.27, corresponding to [M + H]⁺for 3,

from an LC-MS analysis of synthesized 3; (C) EIC for m/z 411.28−

411.29, corresponding to [M + H]⁺for [23-d]-2, from an LC-MS

analysis of synthesized [23-d]-2; (D) EIC for m/z 408.26−408.27,

corresponding to [M + H]⁺for 4, from an LC-MS analysis of extracts

of S. venezuelae MarG fed with 3; (E) EIC for m/z 408.26−408.27,

corresponding to [M + H]⁺for 4, from an LC-MS analysis of extracts

of S. venezuelae MarG fed with [23-d]-2; (F) EIC for m/z 409.27−

409.28, corresponding to [M + H]⁺for [23-d]-4, from LC-MS analysis

of extracts of S. venezuelae MarG fed with [23-d]-2.

(Supporting Information)). The conversion of hydroxy- and

ketoprodiginines (23S)-2, (23R)-2, and 3 to premarinesosin A

by MarG expression strain did not resolve the question of

whether the keto or hydroxyl derivative is the correct

intermediate. We hypothesized that hydroxy- and ketoprodigi-

nines are most likely interconverting via a redox reaction in the

MarG expression host, S. venezuelae (Figure 1 and Scheme 5).

Therefore, we sought the synthesis of [23-d]-23-hydroxyunde-

cylprodiginine ([23-d]-2) to further study the intermediates

involved in marineosin biosynthesis.

Synthesis of [23-d]-23-Hydroxyundecylprodiginine

([23-d]-2) and Subsequent Conversion into Deuterium-

Labeled Premarineosin A ([23-d]-4) via MarG-Catalyzed

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Scheme 7. Synthesis of Racemic [23-d]-23-Hydroxyundecylprodiginine ([23-d]-2)

Scheme 8. Synthesis of A- and B-Ring Functionalized (Hydroxy/alkoxy)undecylprodiginines 2 and 32−38

8 and 9. These compounds and undecylprodiginine (1) were

fed to the MarG expression strain.

Scheme 9. Synthesis of Hydroxyundecylprodiginines 39−41

Containing a Terminal Hydroxyl Group at the Alkyl Chain

Neither premarineosin A (4) nor C9−C21 cyclized

prodiginine was observed at a detectable level after feeding

undecylprodiginine (1), which has no hydroxyl group at C-23

of the alkyl chain (Figure 1). This observation clearly indicates

that the hydroxyl group of 2 is required for the MarG-catalyzed

process and must be introduced early in the pathway. One

option is the hydroxylation of the 2-UP subunit by an

unidentiﬁed oxidase (route 1, Figure 1) or recruitment of 2-

hydroxybutyric acid starter unit by MarP (route 2, Figure 1).

The gene product(s) required for introduction of the hydroxyl

group remains unknown. We also did not observe any C9−C21

cyclized prodiginine related products after feeding of 23-

alkoxyundecylprodiginines 32 and 33 (Scheme 8), further

demonstrating that the hydroxyl group at C-23 is required for

the formation of the spiro-tetrahydropyran-aminal ring and that

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Figure 5. Proposed structures of expected products from feeding of 34−36 and 39−41 to S. venezuelae MarG.

hydroxyundecylprodiginines are the preferred substrates for

MarG. Prodiginines 34−36 with shorter alkyl chain length

(octyl) on ring C and C-alkyl substitutions on rings A and B,

containing the key secondary alcohol substituent, were

synthesized (Scheme 8) and fed to S. venezuelae MarG mutant.

LC-MS analyses clearly demonstrated the production of both

the corresponding premarineosin A and 16-ketopremarineosin

analogues 58−63. The compounds were not isolated and

characterized due to poor conversion of hydroxyundecylprodi-

ginines to premarineosins; however, their corresponding

chemical structures were proposed on the basis of the above

feeding results of S. venezuelae MarG mutant, MS/MS, and LC-

MS analyses (Figure 5 and Figures S5−S8 (Supporting

Information)). Conversely, cyclic products of prodiginines

with N-methylpyrrole and furan in the place of terminal pyrrole

(ring A) (37 and 38, Scheme 8), were not detected via LC-MS

after feeding their respective substrates to the S. venezuelae

MarG expression strain. Interestingly, prodiginines 39−41

(Scheme 9), with a terminal hydroxyl group at the alkyl chain

(primary alcohols), were converted to their corresponding 16-

ketoprodiginines 64−66 (Figure 5), but their corresponding

cyclized products were not detected via LC-MS. These

products 64−66 also were not isolated and characterized, but

their chemical structures were proposed on the basis of the

above feeding results of S. venezuelae MarG mutant and MS

analysis (Figure S9 (Supporting Information)). The above data

demonstrate that MarG catalyzed bicyclization requires the

presence of a free secondary hydroxyl group on an alkyl chain

on ring C but can tolerate C-alkyl substitutions on rings A and

B (notably replacement of the methoxy group). Substitution of

terminal pyrrole (ring A) with other heterocycles does not lead

to cyclized products.

Antimalarial Activity and Cytotoxicity of Prodigi-

nines. All synthesized natural prodiginines 1−3, and their

analogues 32−41, were evaluated for their antimalarial activity

against the chloroquine-sensitive (CQ^S) D6 and the chlor-

oquine-resistant (CQ^R) Dd2 and 7G8 strains of Plasmodium

falciparum with chloroquine (CQ) as a reference drug,²⁷and

the results are shown in Table 2. In parallel, the cytotoxicity of

all tested compounds was also tested against hepatocellular

HepG2 cancer cell line using meﬂoquine (MQ) as a control

drug.^27dThe synthesized prodiginines 2, (23R)-2, (23S)-2, and

3, containing an extra hydroxyl and/or keto group at C-23 of

the alkyl chain, have decreased antimalarial activity and

selectivity in comparison to undecylprodiginine (1), which

has no substitutions on the alkyl chain (Table 2 and Figure 1).

It is noteworthy that the isomer (23S)-2 is only slightly more

potent than the isomer (23R)-2 and racemic compound 2

(Table 2), which demonstrates that the stereochemistry at C-23

does not alter the antimalarial activity. More signiﬁcantly, 23-

alkoxy analogues 32 and 33 have much improved antimalarial

activity and selectivity in comparison to 2 and 3. Indeed, 32 and

Table 2. Antimalarial Activity and Cytotoxicity of

Prodiginines

antimalarial activity (IC₅₀in

a

nM)

b

cytotoxicity (IC₅₀in

SI

a

compd

D6

7.2

Dd2

7.5

7G8

7.0

nM) HepG2

(D6)

1

1713

238

67

2

110

92

98

118

114

100

199

11.3

2.3

7358

(23R)-2

(23S)-2

3

51

7961

86

66

46

9152

139

77

191

7.1

121

10.2

3.7

14667

2682

32

378

486

31

33

5.7

2770

34

383

1084

17

293

1188

15

368

627

24

12050

9385

35

9

36

1757

103

>40

>43

106

193

163

ND

37

>2500

2328

108

59

>2500

80

>2500

1001

168

93

>100000

11416

11363

6184

38

39

40

36

41

38

23

58

c

CQ

MQ

10

102

ND

63

ND

10970

a

IC₅₀values are represented as averages of triplicate measurements

b

(SD 10%). SI (selectivity index) = IC₅₀(cytotoxicity)/IC₅₀(D6).

c

ND: not determined.

33 have antimalarial activity comparable to that of 1, with

slightly reduced toxicity (as measured by activity against

HepG2 cancer cells), and thus oﬀer increased selectivity. In

contrast, retention of the free hydroxyl group on the alkyl

chain, with a reduction in the alkyl chain length, led to a 3-fold

decrease in the antimalarial potency (34 versus 2). Similarly, a

loss of antimalarial activity was observed with replacement of

the OMe group of ring B by methyl groups (35 versus 2),

demonstrating the importance of the methoxy group on ring B

for potency. Surprisingly, prodiginine 36, which contains an

extra alkyl residue (ethyl) on ring A, showed a substantially

higher potency with an IC₅₀of <24 nM against all strains of P.

falciparum (36 versus 2), and it had reduced selectivity.

Replacement of the terminal nonalkylated pyrrole ring (ring A)

of the core moiety by N-methylpyrrole and furan moieties

(compounds 37 and 38) resulted in a large decrease in

antimalarial activity (37 and 38 versus 2). These results,

indicating that the pyrrole NH of the prodiginines is required

for potent antimalarial activity, support our previous ﬁndings.⁷

Our previous studies also demonstrated that undecylprodigi-

nine, with a terminal amine group at the alkyl chain, showed

poor antimalarial activity (IC₅₀= 1700 nM).⁷However,

prodiginines 39−41, with a terminal hydroxyl group at the

alkyl chain (primary alcohols), exhibited better activity (IC₅₀

110 nM). Notably, in these cases, longer alkyl chains led to an

<

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The Journal of Organic Chemistry

Article

with a linear elution gradient ranging from CH₃OH/CH₃CN/H₂O

(40%/10%/50%) to CH₃OH (100%) acidiﬁed with 0.1% triﬂuoro-

acetic acid at a ﬂow rate of 0.3 mL/min.

increase in the antimalarial activity (IC₅₀of 39 (C10) > 40

(C11) > 41 (C12)). These results thus demonstrate that the

presence of hydroxyl and/or keto substituents on the alkyl

chain, replacement of methoxy group of ring B by alkyl

substituents, and replacement of the terminal nonalkylated

pyrrole ring (ring A) by N-methylpyrrole and/or other

heterocycles have an adverse eﬀect on the antimalarial activities.

Conversely, the hydroxyl group of 2 masked with methyl and

benzyl groups, as in 32 and 33, respectively, dramatically

increased the potency and selectivity (Table 2).

Synthesis of 1-(1-(Phenylsulfonyl)-pyrrol-2-yl)pent-4-en-1-ol

(16). To a stirred solution of 15 (4.0 g, 17.02 mmol) in 200 mL of

THF was added 3-butenylmagnesium bromide solution (0.5 M in

THF) (68 mL, 34.04 mmol) at 0 °C, and the reaction mixture was

stirred at 0 °C for 2 h. Then the reaction was quenched by addition of

2 N HCl, with the temperature maintained at <10 °C, and extracted

with diethyl ether (3 × 100 mL). The combined organic extracts were

washed with water and brine and dried over anhydrous Na₂SO₄. The

solvent was evaporated under reduced pressure, and the crude product

was chromatographed on silica gel to aﬀord the title compound 16

CONCLUSIONS

1

■

(4.21 g, 85%) as a syrup: R_f= 0.45 (20% EtOAc/hexanes); H NMR

In summary, we have accomplished the ﬁrst synthesis of (S)-23-

hydroxyundecylprodiginine ((23S)-2), (R)-23-hydroxyundecyl-

prodiginine ((23R)-2)), 23-ketoundecylprodiginine (3), [23-

d]-23-hydroxyundecylprodiginine ([23-d]-2), and their syn-

thetic analogues 32−41 from commercially available starting

materials in straightforward approaches. These feasible

synthetic routes can be carried out on a large scale and are

suited for the generation of a library of novel prodiginines for

their advanced biological activities and SAR studies. Formation

of the critical unusual spiro-tetrahydropyran-aminal ring of

marineosins and conversion of (23S)-2 to premarineosin A (4)

were accomplished by MarG expressed in S. venezuelae.

Conversion of [23-d]-2 to the deuterium-labeled premarineosin

A ([23-d]-4) unambiguously demonstrates that the pathway

directly proceeds stereospeciﬁcally from (23S)-2. The synthesis

of 23-alkoxyundecylprodiginines (32 and 33), 20-hydroxyoctyl-

prodiginine (34), and A- and B-ring functionalized prodiginines

(35−41) was used to investigate the substrate promiscuity of

MarG. As such, this one-step enzymatic (C−C bond formation

and intramolecular hydroalkoxylation) work represents a

complementary approach to the widespread synthetic ap-

proaches directed toward this class of complex natural products.

Investigations to improve the conversion of prodiginines to

premarineosins by MarG and subsequent isolation and

chemical reduction step to the ﬁnal marineosins and their

analogues are underway in our laboratory. Signiﬁcantly, alkoxy

analogues 32 and 33 exhibited potent antimalarial activity with

better selectivity than natural prodiginines 1−3. In the course

of this work, we also have discovered a simple and convenient

method for the synthesis of 5-alkylene-1,5-dihydropyrrol-2-

ones from C-alkyl-substituted pyrroles by using TPAP/NMO.

These pyrrol-2-ones are excellent building blocks for the

synthesis of natural and synthetic products of biological

importance, and further investigations to improve the yields

and expand the substrate scope of the oxidation with this

reagent as well as mechanistic studies are underway in our

laboratory.

(CDCl₃, 400 MHz) δ 7.78 (d, J = 8.1 Hz, 2H), 7.59 (m, 1H), 7.50 (m,

2H), 7.31 (dd, J = 1.7, 3.3 Hz, 1H), 6.29 (m, 2H), 5.72 (m, 1H), 4.93

(m, 2H), 4.85 (m, 1H), 2.92 (br s, 1H), 2.12 (m, 2H), 1.90 (m, 2H);

¹³C NMR (CDCl₃, 100 MHz) δ 139.1, 138.1, 137.8, 134.0, 129.5

(2C), 126.6 (2C), 123.5, 115.1, 112.5, 111.8, 64.5, 34.2, 30.1; HRMS

(ESI) calcd for C₁₅H₁₇NaNO₃S (M + Na)⁺314.0821, found 314.0815;

IR (KBr) ν_max3365, 2956, 2846, 1678, 1425 cm⁻¹.

Synthesis of 2-(4-Pentenyl)pyrrole (11). To a stirred

suspension of LiAlH₄(2.7 g, 72.16 mmol) in dry THF (200 mL)

was added dropwise 16 (3.0 g, 10.30 mmol) in THF (50 mL) at 0 °C,

the reaction mixture was stirred for 3 h at 0 °C, and it was warmed to

room temperature. Then the resulting solution was heated to reﬂux for

12 h. The reaction was quenched with a saturated solution of sodium

sulfate. The insoluble solid was ﬁltrated oﬀ and washed with DCM

(200 mL). Then the combined organic solution was concentrated

under reduced pressure to give the crude product, which was further

chromatographed on silica gel, with ethyl acetate/hexanes as eluent, to

aﬀord 11 (1.14 g, 82%) as a colorless syrup: R_f= 0.80 (20% EtOAc/

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 7.95 (br s, 1H), 6.72 (m,

1H), 6.22 (dd, J = 2.8, 5.8 Hz, 1H), 6.01 (m, 1H), 5.88 (m, 1H), 5.09

(m, 2H), 2.68 (t, J = 7.2 Hz, 2H), 2.18 (m, 2H), 1.80 (m, 2H); ¹³C

NMR (CDCl₃, 100 MHz) δ 138.5, 132.4, 116.2, 115.0, 108.3, 105.1,

33.3, 28.9, 27.1; HRMS (ESI) calcd for C₉H₁₄N (M + H)⁺136.1121,

found 136.1126; IR (KBr) ν_max2931, 2857, 1681, 1439 cm⁻¹.

Representative Procedure for the Synthesis of (S)-2-

Hydroxy-7-octene (12). To a stirred solution of (S)-propylene

oxide (17; 1.0 g, 17.24 mmol) and copper iodide (327 mg, 1.72 mmol)

in 50 mL of THF was added 4-pentenylmagnesium bromide solution

(18; 0.5 M in THF) (52 mL, 25.86 mmol) at 0 °C, and the reaction

mixture was stirred at 0 °C for 2 h. Then the reaction mixture was

quenched by addition of 2 N HCl, with the temperature maintained at

<10 °C, and extracted with diethyl ether (3 × 100 mL). Then the

combined organic extracts were washed with 10% sodium thiosulfate

solution, water, and brine and dried over anhydrous Na₂SO₄. The

solvent was evaporated under reduced pressure, and the crude product

was chromatographed on silica gel to aﬀord the title compound 12

(2.03 g, 92%) as a colorless liquid: R_f= 0.50 (50% EtOAc/hexanes);

¹H NMR (CDCl₃, 400 MHz) δ 5.79 (m, 1H), 4.98−4.92 (m, 2H),

3.80 (m, 1H), 2.04 (m, 2H), 1.40 (m, 6H), 1.18 (d, J = 6.2 Hz, 3H);

¹³C NMR (CDCl₃, 100 MHz) δ 138.9, 114.4, 68.1, 39.2, 33.7, 28.9,

25.2, 23.5; HRMS (ESI) calcd for C₈H₁₆NaO (M + Na)⁺151.1093,

found 151.1079; IR (KBr) ν_max3361, 2972, 2930, 2857, 1640 cm⁻¹.

Compound 13 has the same spectral data.

EXPERIMENTAL SECTION

■

General Considerations. NMR spectra were recorded on a

spectrometer at 400 MHz (¹H) and 100 MHz (¹³C). Experiments

were recorded in CDCl₃and acetone-d₆at 25 °C. Chemical shifts are

given in parts per million (ppm) downﬁeld from internal standard

Me₄Si (TMS). HRMS (ESI) were recorded on a high-resolution

(30000) LTQ-Orbitrap mass spectrometer. Unless otherwise stated, all

reagents and solvents were purchased from commercial suppliers and

used without further puriﬁcation. Reactions which required the use of

anhydrous, inert atmosphere techniques were carried out under an

atmosphere of argon/nitrogen. Chromatography was executed using

silica gel (230−400 mesh) and/or neutral alumina as the stationary

phase and mixtures of ethyl acetate and hexane as eluents. Analytical

HPLC analyses were performed using a C18 column (4.6 × 150 mm)

Representative Procedure for the Synthesis of (S)-11-

(Pyrrol-2-yl)undec-7-en-2-ol (19). Grubbs’ second-generation

catalyst (Grubbs’ II; 160 mg, 0.19 mmol) was added to a stirred

solution of 11 (500 mg, 3.70 mmol), and 12 (948 mg, 7.40 mmol) in

dichloromethane (25 mL) at room temperature. Then the solution

was stirred for 6 h at 40 °C. After completion of the reaction, the

solvent was removed under reduced pressure and the product was

chromatographed on silica gel, with ethyl acetate/hexanes as eluent, to

aﬀord the desired product 19 (390 mg, 45%) as a syrup: R_f= 0.45

1

(30% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 8.15 (br s,

1H), 6.65 (dd, J = 2.5, 6.6 Hz, 1H), 6.13 (dd, J = 2.5, 5.7 Hz, 1H), 5.92

(m, 1H), 5.42 (m, 2H), 3.81 (m, 1H), 2.60 (t, J = 7.6 Hz, 2H), 2.01

(m, 4H), 1.66 (m, 2H), 1.35 (m, 6H), 1.18 (d, J = 6.2 Hz, 3H); ¹³C

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The Journal of Organic Chemistry

Article

NMR (CDCl₃, 100 MHz) δ 132.5, 130.8, 129.9, 116.0, 108.1, 104.8,

68.1, 39.1, 32.4, 32.0, 29.4 (2C), 27.0, 25.1, 23.4; HRMS (ESI) calcd

for C₁₅H₂₅NaNO (M + Na)⁺258.1828, found 258.1819; IR (KBr)

ν_max3381, 2928, 2856, 1679, 1437 cm⁻¹. Compound 21 has the same

spectral data.

(CDCl₃, 100 MHz) δ 209.4, 173.5, 138.7, 138.5, 123.6, 118.6, 43.7,

29.8, 29.2 (2C), 29.1 (2C), 29.0, 27.8, 23.8; HRMS (ESI) calcd for

C₁₅H₂₄NO₂(M + H)⁺250.1802, found 250.1794; IR (KBr) ν_max3290,

2951, 2847, 1704, 1404 cm⁻¹.

Synthesis of 23-Ketoundecylprodiginine (3). Compound 3

(32.1 mg, 50%) was synthesized by the same procedure as described

Representative Procedure for the Synthesis of (10′S)-

Hydroxyundecylpyrrole ((10′S)-9). To a degassed solution of 19

(200 mg, 0.85 mmol) in methanol (10 mL) was added a catalytic

amount of 10% Pd/C. The reaction mixture was stirred at room

temperature for 12 h under hydrogen gas. After replacement of air by

nitrogen, Pd/C was ﬁltered oﬀ and methanol was evaporated under

reduced pressure. The crude product was chromatographed on silica

gel to aﬀord the title compound (10′S)-9 (190 mg, 95%) as a white

solid: mp 43−45 °C; R_f= 0.56 (20% EtOAc/hexanes); ¹H NMR

(CDCl₃, 400 MHz) δ 8.01 (br s, 1H), 6.66 (m, 1H), 6.13 (dd, J = 2.8,

5.7 Hz, 1H), 5.91 (m, 1H), 3.80 (m, 1H), 2.59 (t, J = 7.4 Hz, 2H),

1.65−1.58 (m, 3H), 1.47−1.29 (m, 13H), 1.18 (d, J = 6.2 Hz, 3H);

¹³C NMR (CDCl₃, 100 MHz) δ 132.9, 116.0, 108.2, 104.8, 68.2, 39.4,

1

for (23S)-2: mp 97−99 °C; R_f= 0.32 (70% EtOAc/hexanes); H

NMR (acetone-d₆, 400 MHz) δ 6.91 (br s, 1H), 6.76 (br s, 2H), 6.55

(br s, 1H), 6.20 (br s, 2H), 5.96 (br s, 1H), 3.93 (s, 3H), 2.55 (t, J =

6.2 Hz, 2H), 2.43 (t, J = 7.3 Hz, 2H), 2.05 (s, 3H), 1.59−1.49 (m,

4H), 1.36−1.23 (m, 10H); ¹³C NMR (acetone-d₆, 100 MHz) δ 208.1,

169.3, 160.0, 143.2, 141.3, 130.1, 129.6, 123.0, 120.3, 115.6, 113.3,

110.9, 109.5, 96.2, 58.8, 43.8, 30.6, 30.2−29.7 (six carbons are

merged), 28.5, 24.5; HRMS (ESI) calcd for C₂₅H₃₄N₃O₂(M + H)⁺

408.2646, found 408.2635; IR (KBr) ν_max3127, 2927, 2848, 1702,

1576, 1490 cm⁻¹.

Synthesis of 5-Ethylidene-1,5-dihydropyrrol-2-one (25a), 3-

Methyl-5-methylene-1,5-dihydropyrrol-2-one (25b), 4-Ethyl-3-

methyl-5-methylene-1,5-dihydropyrrol-2-one (25c), and 1-(5-

Ethyl-1-methylpyrrol-2-yl)propan-1-one (25d). Compounds 25a

(92 mg, 32%), 25b (100 mg, 35%), 25c (108 mg, 39%), and 25d (220

mg, 89%) were synthesized by the same procedure as described for 22.

5-Ethylidene-1,5-dihydropyrrol-2-one (25a): mp 106−108 °C; R_f

29.7, 29.6 (2C), 29.5, 29.4 (2C), 27.7, 25.8, 23.5; HRMS (ESI) calcd

for C₁₅H₂₈NO (M + H)⁺238.2165, found 238.2159; IR (KBr) ν_max

3511, 3243, 2923, 2849, 1574, 1470 cm⁻¹. Compound (10′R)-9 has

the same spectral data.

Representative Procedure for the Synthesis of (S)-23-

Hydroxyundecylprodiginines ((23S)-2). To a stirred suspension

of MBC (8; 75 mg, 0.39 mmol) and (10′S)-9 (187 mg, 0.78 mmol) in

anhydrous methanol (10 mL) was added methanolic 2 N HCl

(catalytic amount) at room temperature. The resulting brightly

colored solution was stirred for 5 h at same temperature. The

methanol was removed under reduced pressure, and the crude material

was dissolved in ethyl acetate (75 mL) and washed with saturated

NaHCO₃solution (2 × 25 mL). The organic layer was dried over

anhydrous Na₂SO₄, solvent was removed under reduced pressure, and

the crude product was chromatographed on neutral alumina as the

stationary phase and hexane/ethyl acetate as the mobile phase to

aﬀord the desired (23S)-2 (102 mg, 63%): mp 93−95 °C; R_f= 0.30

1

= 0.45 (50% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 10.09

(br s, 1H), 6.89 (dd, J = 1.4, 5.5 Hz, 1H), 6.10 (d, J = 5.3 Hz, 1H),

5.34 (q, J = 7.5 Hz, 1H), 1.96 (d, J = 7.5 Hz, 3H); ¹³C NMR (CDCl₃,

100 MHz) δ 173.9, 139.7, 138.4, 123.5, 113.5, 13.4; HRMS (ESI)

calcd for C₆H₈NO (M + H)⁺110.0600, found 110.0596; IR (KBr)

ν_max3165, 2809, 1685, 1652, 1400 cm⁻¹.

3-Methyl-5-methylene-1,5-dihydropyrrol-2-one (25b): mp >200

1

°C; R_f= 0.40 (70% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ

9.15 (br s, 1H), 6.62 (t, J = 1.4 Hz, 1H), 4.92 (s, 1H), 4.71 (s, 1H),

1.94 (d, J = 1.4 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 173.7, 142.8,

135.5, 132.1, 96.7, 10.6; HRMS (ESI) calcd for C₆H₈NO (M + H)⁺

110.0600, found 110.0598; IR (KBr) ν_max3156, 2807, 1679, 1648

cm⁻¹.

1

(70% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 6.86 (s, 1H),

6.67 (dd, J = 1.1, 3.6 Hz, 1H), 6.61 (dd, J = 1.1, 2.7 Hz, 1H), 6.45 (d, J

= 3.6 Hz, 1H), 6.11 (dd, J = 2.7, 3.6 Hz, 1H), 6.08 (s, 1H), 5.82 (d, J =

3.6 Hz, 1H), 3.97 (s, 3H), 3.79 (m, 1H), 2.05 (t, J = 7.6 Hz, 2H),

1.46−1.12 (m, 16H), 1.19 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100

MHz) δ 169.1, 160.2, 144.7, 138.5, 128.4, 128.3, 123.0, 121.1, 116.0,

112.9, 110.0, 108.6, 95.7, 68.2, 58.4, 39.4, 29.7, 29.6 (3C), 29.4, 29.2,

27.3, 25.8, 23.5; HRMS (ESI) calcd for C₂₅H₃₆N₃O₂(M + H)⁺

410.2802, found 410.2791; IR (KBr) ν_max3368, 3227, 2925, 2851,

1606, 1574, 1192 cm⁻¹. Compound (23R)-2 has the same spectral

data.

Synthesis of 10′-Ketoundecylpyrrole (22). Tetrapropylammo-

nium perruthenate (TPAP; 44 mg, 0.12 mmol) was added to a stirred

solution of (10′S)-9 (200 mg, 0.84 mmol), NMO (197 mg, 1.68

mmol), and 4 Å molecular sieves (1.0 g) in dichloromethane (10 mL)

at 0 °C. The solution was warmed to room temperature and stirred for

1.5 h. The reaction mixture was ﬁltered through Celite and washed

with dichloromethane (100 mL). The ﬁltrate was concentrated under

reduced pressure to give a crude residue, which was further

chromatographed on silica gel, with ethyl acetate/hexanes as eluent,

to aﬀord 22 (101 mg, 51%), and 23 (31 mg, 15%).

10′-Ketoundecylpyrrole (22): mp 58−60 °C; R_f= 0.65 (20%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 7.94 (br s, 1H), 6.65

(dd, J = 1.4, 3.8 Hz, 1H), 6.12 (dd, J = 3.8, 5.7 Hz, 1H), 5.90 (br s,

1H), 2.59 (t, J = 7.8 Hz, 2H), 2.41 (t, J = 7.6 Hz, 2H), 2.13 (s, 3H),

1.64−1.54 (m, 4H), 1.35−1.27 (m, 10H); ¹³C NMR (CDCl₃, 100

MHz) δ 209.5, 132.8, 116.0, 108.2, 104.8, 43.8, 29.9, 29.7, 29.3 (4C),

29.1, 27.7, 23.8; HRMS (ESI) calcd for C₁₅H₂₆NO (M + H)⁺

236.2009, found 236.2002; IR (KBr) ν_max3290, 2951, 2847, 1704,

1404 cm⁻¹.

4-Ethyl-3-methyl-5-methylene-1,5-dihydropyrrol-2-one (25c): mp

90−92 °C; R_f= 0.52 (50% EtOAc/hexanes); H NMR (CDCl₃, 400

MHz) δ 8.93 (br s, 1H), 4.87 (d, J = 1.2 Hz, 1H), 4.77 (s, 1H), 2.40

(q, J = 7.6 Hz, 2H), 1.85 (s, 3H), 1.09 (t, J = 7.6 Hz, 3H); ¹³C NMR

(CDCl₃, 100 MHz) δ 173.4, 146.0, 143.6, 129.1, 93.2, 17.7, 14.3, 8.3;

HRMS (ESI) calcd for C₈H₁₁NaNO (M + Na)⁺160.0733, found

160.0736; IR (KBr) ν_max3163, 2812, 1678 cm⁻¹.

1

1-(5-Ethyl-1-methylpyrrol-2-yl)propan-1-one (25d): mp 32−34

1

°C; R_f= 0.75 (20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ

6.93 (d, J = 4.0 Hz, 1H), 5.94 (d, J = 4.0 Hz, 1H), 3.86 (s, 3H), 2.77

(q, J = 7.5 Hz, 2H), 2.58 (q, J = 7.5 Hz, 2H), 1.26 (t, J = 7.5 Hz, 3H),

1.17 (t, J = 7.5 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.6, 144.2,

130.3, 118.6, 106.0, 32.8, 32.1, 19.8, 12.4, 9.4; HRMS (ESI) calcd for

C₁₀H₁₆NO (M + H)⁺166.1226, found 166.1222; IR (KBr) ν_max2974,

1644, 1485 cm⁻¹.

Synthesis of 10-Hydroxyundecanoic Acid (27). Au(IPr)Cl

(136 mg, 0.22 mmol), AgO₂CCF₃(49 mg, 0.22 mmol), Shvo’s catalyst

(239 mg, 0.22 mmol), 10-undecynoic acid (26; 2.0 g, 10.98 mmol),

H₂O (7 mL, 373.6 mmol), and isopropyl alcohol (IPA) (43 mL) were

placed in a sealed tube with a Teﬂon-lined cap under an argon

atmosphere at room temperature. The reaction mixture was stirred

and heated for 48 h at 70 °C. The mixture was ﬁltered through Celite

and washed with dichloromethane (200 mL). The ﬁltrate was

concentrated under reduced pressure to give a crude orange residue,

which was further chromatographed on silica gel, with ethyl acetate/

hexanes as eluent, to aﬀord the pure 10-hydroxyundecanoic acid (27)

as a white solid (1.82 g, 82%): mp 46−48 °C; R_f= 0.35 (70% EtOAc/

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 3.79 (m, 1H), 2.32 (t, J =

7.4 Hz, 2H), 1.59 (m, 2H), 1.44−1.24 (m, 12H), 1.17 (d, J = 6.2 Hz,

3H); ¹³C NMR (CDCl₃, 100 MHz) δ 179.4, 68.3, 39.2, 34.0, 29.5,

29.3, 29.2, 29.0, 25.6, 24.7, 23.3; HRMS (ESI) calcd for C₁₁H₂₂NaO₃

(M + Na)⁺225.1461, found 225.1463; IR (KBr) ν_max3450, 2934,

2853, 1728, 1220 cm⁻¹.

5-(10-Oxoundecylidene)-1,5-dihydropyrrol-2-one (23): mp 38−40

°C; R_f= 0.25 (20% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ

9.67 (br s, 1H), 6.89 (dd, J = 1.6, 5.5 Hz, 1H), 6.09 (dd, J = 0.8, 5.5

Hz, 1H), 5.25 (t, J = 8.0 Hz, 1H), 2.37 (t, J = 7.4 Hz, 2H), 2.33 (m,

2H), 2.10 (s, 3H), 1.54−1.42 (m, 4H), 1.32−1.24 (m, 8H); ¹³C NMR

11683

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Synthesis of 10-Oxoundecanoic Acid (28). To a stirred

solution of 27 (1.0 g, 4.95 mmol) in anhydrous CH₂Cl₂(50 mL)

was added Dess−Martin periodinane (DMP; 3.14 g, 7.42 mmol) at 0

°C. The mixture was stirred at room temperature for 10 h, and then

the solvent was evaporated, and diethyl ether was added to the crude

product, and the reaction mixture was stirred until a white solid was

formed. The reaction mixture was ﬁltered through Celite and washed

with diethyl ether (200 mL). The ﬁltrate was concentrated under

reduced pressure to give a crude residue, which was further

chromatographed on silica gel, with ethyl acetate/hexanes as eluent,

to aﬀord the pure product 28 as a white solid (881 mg, 89%): mp 51−

53 °C; R_f= 0.45 (70% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz)

δ 2.40 (t, J = 7.4 Hz, 2H), 2.32 (t, J = 7.4 Hz, 2H), 2.11 (m, 3H),

1.64−1.50 (m, 4H), 1.27 (m, 8H); ¹³C NMR (CDCl₃, 100 MHz) δ

209.6, 180.0, 43.7, 34.0, 29.8, 29.1, 29.0 (2C), 28.9, 24.6, 23.8; HRMS

(ESI) calcd for C₁₁H₂₁O₃(M + H)⁺. 201.1485, found 201.1486; IR

(KBr) ν_max2921, 2845, 1726, 1701, 1235 cm⁻¹.

38.0, 35.8, 29.4 (4C), 25.3 (2C), 21.4, 19.9; HRMS (ESI) calcd for

C₁₇H₂₇DNO₃(M + H)⁺295.2127, found 295.2126; IR (KBr) ν_max

3283, 2930, 2856, 1734, 1639, 1404, 1265 cm⁻¹.

11-Oxo-11-(pyrrol-3-yl)undecan-2-yl-2-d acetate ([10′-d]-31):

syrup; R_f= 0.25 (20% EtOAc/hexanes); ¹H NMR (CDCl₃, 400

MHz) δ 9.49 (br s, 1H), 7.41 (m, 1H), 6.75 (dd, J = 2.5, 4.7 Hz, 1H),

6.32 (dd, J = 2.6, 4.0 Hz, 1H), 2.73 (t, J = 7.4 Hz, 2H), 2.01 (s, 3H),

1.68 (m, 2H), 1.52 (m, 1H), 1.44 (m, 1H), 1.32−1.26 (m, 10H), 1.17

(s, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 197.2, 171.0, 125.8, 123.4,

119.5, 108.6, 70.8 (t, C-23), 39.7, 35.8, 29.4 (4C), 25.3, 25.1, 21.4,

19.8; HRMS (ESI) calcd for C₁₇H₂₇DNO₃(M + H)⁺295.2127, found

295.2125; IR (KBr) ν_max3281, 2929, 2853, 1729, 1664, 1404.

Representative Procedure for the Synthesis of [10′-d]-

Hydroxyundecylpyrrole ([10′-d]-9). To a stirred solution of [10′-

d]-30 (500 mg, 1.70 mmol) in 100 mL of isopropyl alcohol (IPA) at

25 °C was added slowly sodium borohydride (NaBH₄) (755 mg, 20.40

mmol), and the reaction mixture was heated at reﬂux for 12 h. The hot

reaction mixture was poured into 100 mL of ice water, and the

solution was acidiﬁed with 2 N HCl. The suspension was extracted

with dichloromethane (3 × 50 mL), and the combined organic extracts

were washed with water and brine and dried over anhydrous Na₂SO₄.

The solvent was evaporated under reduced pressure, and the crude

product was chromatographed on silica gel to aﬀord the title

compound ([10′-d]-9 (271 mg, 67%) as a white solid: mp 46−48

Synthesis of [10-d]-10-Hydroxyundecanoic Acid ([10-d]-27).

To a stirred solution of 28 (850 mg, 4.25 mmol) in anhydrous

methanol (15 mL) was added slowly NaBD₄(209 mg, 5.10 mmol) at

0 °C, and the reaction mixture was stirred at the same temperature for

2 h. The resulting solution was quenched with 1 N HCl and extracted

with ethyl acetate (3 × 50 mL), and the combined extracts were

washed with water and brine, dried over anhydrous Na₂SO₄, and

concentrated under reduced pressure. The crude residue was further

chromatographed on silica gel, with ethyl acetate/hexanes as eluent, to

aﬀord the pure product [10-d]-27 as a white solid (690 mg, 80%): mp

1

°C; R_f= 0.55 (20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ

7.99 (br s, 1H), 6.66 (dd, J = 2.7, 4.0 Hz, 1H), 6.13 (dd, J = 2.7, 5.7

Hz, 1H), 5.91 (m, 1H), 2.59 (t, J = 7.4 Hz, 2H), 1.64−1.58 (m, 2H),

1.47−1.27 (m, 14H), 1.18 (s, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ

132.9, 116.0, 108.2, 104.8, 67.7 (t, C-23), 39.2, 29.7, 29.6 (2C), 29.5,

29.4 (2C), 27.7, 25.7, 23.4; HRMS (ESI) calcd for C₁₅H₂₇DNO (M +

H)⁺239.2228, found 239.2227; IR (KBr) ν_max3511, 3243, 2923, 2849,

1574, 1470 cm⁻¹.

1

45−47 °C; R_f= 0.35 (70% EtOAc/hexanes); H NMR (CDCl₃, 400

MHz) δ 2.32 (t, J = 7.4 Hz, 2H), 1.59 (m, 2H), 1.44−1.24 (m, 12H),

1.17 (s, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 179.4, 67.8 (t, C-23),

39.0, 34.1, 29.5, 29.3, 29.1, 29.0, 25.6, 24.7, 23.2; HRMS (ESI) calcd

for C₁₁H₂₁DNaO₃(M + Na)⁺226.1522, found 226.1523; IR (KBr)

ν_max3450, 2934, 2853, 1728, 1220 cm⁻¹.

Synthesis of [23-d]-23-Hydroxyundecylprodiginine ([23-d]-

2). Compound [23-d]-2 (113 mg, 70%) was synthesized by the same

procedure as described for (23S)-2: mp 94−96 °C; R_f= 0.70 (20%

Representative Procedure for the Synthesis of [10-d]-10-

Acetoxyundecanoic Acid ([10-d]-29). Acetic anhydride (Ac₂O;

1.88 g, 18.47 mmol) was added to a stirred solution of [10-d]-27 (1.5

g, 7.39 mmol) in pyridine (10 mL), and the reaction mixture was

stirred for 12 h at room temperature. The reaction mixture was diluted

with ethyl acetate (200 mL), the solution was washed with 2 N HCl (3

× 50 mL) and brine, dried over anhydrous Na₂SO₄, and ﬁltered, and

the solvent was removed by rotary evaporation to furnish the crude

product. The crude compound was chromatographed on silica gel

using hexane/ethyl acetate as the mobile phase to aﬀord [10-d]-29

1

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 6.86 (s, 1H), 6.67

(dd, J = 1.1, 3.6 Hz, 1H), 6.61 (dd, J = 1.1, 2.7 Hz, 1H), 6.45 (d, J =

3.6 Hz, 1H), 6.11 (dd, J = 2.7, 3.6 Hz, 1H), 6.08 (s, 1H), 5.82 (d, J =

3.6 Hz, 1H), 3.97 (s, 3H), 2.05 (t, J = 7.6 Hz, 2H), 1.46−1.15 (m,

19H); ¹³C NMR (CDCl₃, 100 MHz) δ 169.1, 160.2, 144.7, 138.7,

128.3, 128.2, 123.1, 121.2, 116.0, 112.9, 110.0, 108.6, 95.8, 67.7 (t, C-

23), 58.4, 39.4, 29.7, 29.6 (3C), 29.4, 29.2, 27.3, 25.8, 23.5; HRMS

(ESI) calcd for C₂₅H₃₅DN₃O₂(M + H)⁺411.2865, found 411.2860;

IR (KBr) ν_max3368, 3227, 2925, 2851, 1606, 1574, 1192 cm⁻¹.

Synthesis of 7-Hydroxyoctanoic Acid (42). Compound 42

(1.62 g, 80%) was synthesized from 7-oxooctanoic acid by the same

procedure as described for [10-d]-27 using NaBH₄: syrup; R_f= 0.25

(60% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 3.77 (m, 1H),

2.31 (t, J = 7.4 Hz, 2H), 1.61 (m, 2H), 1.43−1.30 (m, 6H), 1.16 (t, J =

6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 179.1, 68.1, 38.8, 34.0,

29.0, 25.3, 24.6, 23.2; HRMS (ESI) calcd for C₈H₁₆NaO₃(M + Na)⁺

183.0992, found 183.0987; IR (KBr) ν_max3417, 2935, 2861, 1731,

1713 cm⁻¹.

Synthesis of 10-Acetoxyundecanoic Acid (29). Compound 29

(1.72 g, 95%) was synthesized by the same procedure as described for

[10-d]-29: syrup; R_f= 0.50 (40% EtOAc/hexanes); ¹H NMR (CDCl₃,

400 MHz) δ 4.85 (m, 1H), 2.31 (t, J = 7.5 Hz, 2H), 2.00 (s, 3H),

1.64−1.53 (m, 3H), 1.44 (m, 1H), 1.33−1.22 (m, 10H), 1.16 (d, J =

6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 180.0, 170.9, 71.1, 35.9,

34.0, 29.3, 29.2, 29.1, 29.0, 25.3, 24.6, 21.4, 19.9; HRMS (ESI) calcd

for C₁₃H₂₅O₄(M + H)⁺245.1747, found 245.1740; IR (KBr) ν_max

2931, 2857, 1743, 1730, 1245 cm⁻¹.

1

(1.70 g, 94%) as a syrup: R_f= 0.50 (40% EtOAc/hexanes); H NMR

(CDCl₃, 400 MHz) δ 2.42 (m, 2H), 2.00 (s, 3H), 1.65−1.26 (m,

14H), 1.17 (s, 3H); HRMS (ESI) calcd for C₁₃H₂₄DO₄(M + H)⁺

246.1810, found 246.1811; IR (KBr) ν_max2931, 2857, 1742, 1710,

1264 cm⁻¹.

Representative Procedure for the Synthesis of 11-Oxo-11-

(pyrrol-2-yl)undecan-2-yl-2-d Acetate ([10′-d]-30) and 11-Oxo-

11-(pyrrol-3-yl)undecan-2-yl-2-d Acetate ([10′-d]-31). To a

stirred solution of [10-d]-29 (1.5 g, 6.12 mmol) and dimethylforma-

mide (DMF; catalytic amount) in toluene (10 mL) was added thionyl

chloride (SOCl₂; 1.32 mL, 18.36 mmol). The resulting solution was

stirred at 80 °C for 2 h. After all solvents were removed in vacuo, the

residue was dissolved in toluene (50 mL), and this solution was

transferred into a stirred solution of pyrrole (250 mg, 3.73 mmol) and

Zn powder (485 mg, 7.46 mmol) in toluene (100 mL). After

completion of the reaction (monitored by TLC, 2 h), the reaction

mixture was ﬁltered through Celite and washed with dichloromethane

(200 mL). The ﬁltrate was concentrated under reduced pressure to

give a crude residue, which was further chromatographed on silica gel,

with ethyl acetate/hexanes as eluent, to aﬀord the pure [10′-d]-30

(625 mg, 57%), and [10′-d]-31 (88 mg, 8%).

Synthesis of 10-Methoxyundecanoic Acid (43). To a stirred

solution of 27 (1.0 g, 4.95 mmol) in DMF (20 mL) was added

gradually NaH (237 mg, 9.90 mmol) at 0 °C. The resulting suspension

was stirred for 30 min, and methyl iodide (CH₃I) (1.05 g, 7.42 mmol)

was added over 10 min at the same temperature. Then the reaction

mixture was warmed to room temperature and stirring was continued

for 12 h. After completion of the reaction, the reaction mixture was

gradually poured into ice cold water and extracted with ethyl acetate (3

11-Oxo-11-(pyrrol-2-yl)undecan-2-yl-2-d acetate ([10′-d]-30):

syrup; R_f= 0.55 (20% EtOAc/hexanes); ¹H NMR (CDCl₃, 400

MHz) δ 10.00 (br s, 1H), 7.02 (m, 1H), 6.90 (m, 1H), 6.25 (m, 1H),

2.74 (t, J = 7.4 Hz, 2H), 2.01 (s, 3H), 1.70 (m, 2H), 1.54 (m, 1H),

1.42 (m, 1H), 1.35−1.26 (m, 10H), 1.19 (s, 3H); ¹³C NMR (CDCl₃,

100 MHz) δ 191.3, 170.8, 132.0, 124.8, 116.3, 110.5, 71.7 (t, C-23),

11684

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× 100 mL). The combined organic layers were washed with water and

brine. The solvent was evaporated under reduced pressure to give the

crude product, which was dissolved in THF (20 mL), and aqueous 5 N

NaOH (10 mL) was added. The resulting solution was stirred at 60 °C

for 3 h, and then it was acidiﬁed (pH ∼6) by 2 N HCl and extracted

with ethyl acetate (3 × 100 mL). The combined organic extracts were

washed with water and brine and dried over anhydrous Na₂SO₄. The

solvent was evaporated under reduced pressure to aﬀord the pure

product 43 (866 mg, 81%) as a syrup: R_f= 0.35 (30% EtOAc/

hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 3.32 (s, 3H), 3.30 (m, 1H),

2.33 (t, J = 7.5 Hz, 2H), 1.64−1.61 (m, 3H), 1.34−1.18 (m, 11H),

1.12 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 179.7, 77.0,

55.8, 36.2, 34.1, 29.6, 29.4, 29.2, 29.0, 25.4, 24.7, 18.9; HRMS (ESI)

calcd for C₁₂H₂₄NaO₃(M + Na)⁺239.1618, found 239.1619; IR

(KBr) ν_max2930, 2855, 1738, 1710, 1463 cm⁻¹.

1H), 2.77 (t, J = 7.5 Hz, 2H), 1.72 (m, 2H), 1.55 (m, 1H), 1.38−1.30

(m, 11H), 1.13 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ

191.5, 132.0, 124.8, 116.5, 110.5, 76.9, 55.9, 38.0, 36.3, 29.7, 29.4 (3C),

25.9 (2C), 19.0; HRMS (ESI) calcd for C₁₆H₂₇NaNO₂(M + Na)⁺

288.1934, found 288.1933; IR (KBr) ν_max3282, 2929, 2855, 1738,

1639, 1405 cm⁻¹.

10-Methoxy-1-(pyrrol-3-yl)undecan-1-one (46b): syrup; R_f= 0.25

1

(20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 9.50 (br s,

1H), 7.42 (m, 1H), 6.78 (dd, J = 2.5, 4.8 Hz, 1H), 6.64 (dd, J = 2.5, 4.2

Hz, 1H), 3.32 (s, 3H), 3.30 (m, 1H), 2.75 (t, J = 7.4 Hz, 2H), 1.70 (m,

2H), 1.50 (m, 1H), 1.34−1.26 (m, 11H), 1.12 (d, J = 6.2 Hz, 3H); ¹³C

NMR (CDCl₃, 100 MHz) δ 197.3, 125.8, 123.3, 119.5, 108.7, 77.0,

55.9, 39.7, 36.3, 29.7, 29.5 (2C), 29.4, 25.4, 25.2, 19.0; HRMS (ESI)

calcd for C₁₆H₂₇NaNO₂(M + Na)⁺288.1934, found 288.1936; IR

(KBr) ν_max3279, 2933, 2848, 1737, 1654, 1402 cm⁻¹.

Synthesis of 10-(Benzyloxy)undecanoic Acid (44). A stirred

solution of 2-benzyloxy-1-methylpyridinium triﬂate (Dudley reagent;²⁸

3.45 g, 9.90 mmol), MgO (396 mg, 9.90 mmol), and compound 27

(1.0 g, 4.95 mmol) in toluene (75 mL) was heated at 85 °C for 24 h.

The reaction mixture was cooled to room temperature, ﬁltered

through Celite, and washed with dichloromethane (100 mL). The

ﬁltrate was concentrated under vacuum, the obtained crude product

was dissolved in THF (20 mL), and aqueous 5 N NaOH (10 mL) was

added. The resulting solution was stirred at 60 °C for 3 h and then

acidiﬁed (pH ∼6) by 2 N HCl and extracted with ethyl acetate (3 ×

100 mL). The combined organic extracts were washed with water and

brine and dried over anhydrous Na₂SO₄. The solvent was evaporated

under reduced pressure to aﬀord the pure product 44 (1.09 g, 76%) as

10-(Benzyloxy)-1-(pyrrol-2-yl)undecan-1-one (47a): syrup; R_f=

0.65 (20% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 10.01 (br

s, 1H), 7.37−7.30 (m, 5H), 7.05 (m, 1H), 6.94 (m, 1H), 6.29 (m, 1H),

4.65 (d, J = 11.8 Hz, 1H), 4.49 (d, J = 11.8 Hz, 1H), 3.54 (m, 1H),

2.79 (t, J = 7.4 Hz, 2H), 1.77−1.62 (m, 3H), 1.39−1.31 (m, 11H),

1.21 (d, J = 6.3 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.4, 139.2,

132.1, 128.3 (2C), 127.6 (2C), 127.4, 124.7, 116.2, 110.5, 74.9, 70.3,

38.1, 36.7, 29.7, 29.5 (2C), 29.4, 25.5, 25.4, 19.7; HRMS (ESI) calcd

for C₂₂H₃₁NaNO₂(M + Na)⁺364.2247, found 364.2243; IR (KBr)

ν_max3281, 2928, 2854, 1637, 1546, 1404 cm⁻¹.

10-(Benzyloxy)-1-(pyrrol-3-yl)undecan-1-one (47b): syrup; R_f=

1

0.30 (20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 9.61 (br

s, 1H), 7.39−7.30 (m, 6H), 6.71 (dd, J = 2.7, 4.9 Hz, 1H), 6.64 (m,

1H), 4.60 (d, J = 11.8 Hz, 1H), 4.50 (d, J = 11.8 Hz, 1H), 3.55 (m,

1H), 2.77 (t, J = 7.4 Hz, 2H), 1.75−1.52 (m, 3H), 1.47−1.26 (m,

11H), 1.23 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 197.4,

139.0, 128.4 (2C), 127.8 (2C), 127.5, 125.8, 123.4, 119.6, 108.5, 75.1,

70.4, 39.8, 36.7, 29.7, 29.5 (3C), 25.5, 25.2, 19.7; HRMS (ESI) calcd

for C₂₂H₃₁NaNO₂(M + Na)⁺364.2247, found 364.2245; IR (KBr)

ν_max3278, 2931, 2848, 1655, 1401 cm⁻¹.

1

a syrup: R_f= 0.30 (30% EtOAc/hexanes); H NMR (CDCl₃, 400

MHz) δ 7.36−2.28 (m, 5H), 4.59 (d, J = 11.8 Hz, 1H), 4.49 (d, J =

11.8 Hz, 1H), 3.52 (m, 1H), 2.36 (t, J = 7.4 Hz, 2H), 1.67−1.61 (m,

3H), 1.45−1.35 (m, 11H), 1.18 (d, J = 6.2 Hz, 3H); ¹³C NMR

(CDCl₃, 100 MHz) δ 180.0, 139.1, 128.3 (2C), 127.7 (2C), 127.4,

74.9, 70.3, 36.6, 34.1, 29.6, 29.4, 29.2, 29.1, 25.5, 24.7, 19.6; HRMS

(ESI) calcd for C₁₈H₂₈NaO₃(M + Na)⁺315.1931, found 315.1930; IR

(KBr) ν_max3030, 2929, 2855, 1731, 1454 cm⁻¹.

Synthesis of 7-Acetoxyoctanoic Acid (45). Compound 45

(1.78 g, 94%) was synthesized by the same procedure as described for

[10-d]-29: syrup; R_f= 0.55 (60% EtOAc/hexanes); ¹H NMR (CDCl₃,

400 MHz) δ 4.86 (m, 1H), 2.31 (t, J = 7.4 Hz, 2H), 2.00 (s, 3H),

1.62−1.28 (m, 8H), 1.16 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100

MHz) δ 179.6, 171.0, 71.0, 35.6, 33.9, 28.8, 25.0, 24.5, 21.3, 19.9;

HRMS (ESI) calcd for C₁₀H₁₈NaO₄(M + Na)⁺225.1097, found

225.1088; IR (KBr) ν_max2977, 2939, 2863, 1738, 1710, 1374, 1246

cm⁻¹.

8-Oxo-8-(pyrrol-2-yl)octan-2-yl acetate (48a): syrup; R_f= 0.55

1

(50% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 10.15 (br s,

1H), 7.03 (m, 1H), 6.90 (m, 1H), 6.24 (m, 1H), 4.85 (m, 1H), 2.74 (t,

J = 7.4 Hz, 2H), 2.00 (s, 3H), 1.72−1.19 (m, 8H), 1.17 (d, J = 6.2 Hz,

3H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.2, 170.8, 131.9, 125.0,

116.5, 110.5, 70.9, 37.8, 35.7, 29.2, 25.2, 25.2, 21.3, 19.9; HRMS (ESI)

calcd for C₁₄H₂₂NO₃(M + H)⁺252.1594, found 252.1596; IR (KBr)

ν_max3284, 2937, 2861, 1733, 1639, 1404, 1248 cm⁻¹.

8-Oxo-8-(pyrrol-3-yl)octan-2-yl acetate (48b): syrup; R_f= 0.25

1

(50% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 9.48 (br s,

Synthesis of 30, 31, 46a,b, 47a,b, and 48a,b. Compounds 30

(600 mg, 55%), 31 (76 mg, 7%), 46a (450 mg, 65%), 46b (62.2 mg,

9%), 47a (560 mg, 63%), 47b (71.2 mg, 8%), 48a (496 mg, 53%), and

48b (94 mg, 10%) were synthesized by the same procedure as

described for [10′-d]-30 and [10′-d]-31.

1H), 7.41 (m, 1H), 6.75 (dd, J = 2.3, 4.8 Hz, 1H), 6.62 (dd, J = 2.3, 4.2

Hz, 1H), 4.85 (m, 1H), 2.73 (t, J = 7.4 Hz, 2H), 2.00 (s, 3H), 1.71−

1.30 (m, 8H), 1.16 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz)

δ 197.0, 171.0, 125.8, 123.3, 119.5, 108.6, 71.0, 39.5, 35.7, 29.2, 25.2,

24.9, 21.4, 19.9; HRMS (ESI) calcd for C₁₄H₂₂NO₃(M + H)⁺

252.1594, found 252.1589; IR (KBr) ν_max3281, 2931, 2858, 1731,

1654, 1400 cm⁻¹.

11-Oxo-11-(pyrrol-2-yl)undecan-2-yl acetate (30): syrup; R_f=

0.55 (20% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 10.18 (br

s, 1H), 7.05 (m, 1H), 6.93 (m, 1H), 6.26 (m, 1H), 4.88 (m, 1H), 2.76

(t, J = 7.4 Hz, 2H), 2.02 (s, 3H), 1.73−1.26 (m, 14H), 1.19 (d, J = 6.2

Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.5, 170.8, 132.0, 125.0,

116.6, 110.5, 71.1, 38.0, 35.9, 29.4 (4C), 29.3, 25.3, 21.4, 19.9; HRMS

(ESI) calcd for C₁₇H₂₈NO₃(M + H)⁺294.2064, found 294.2057; IR

(KBr) ν_max3282, 2930, 2856, 1736, 1639, 1410, 1247 cm⁻¹.

11-Oxo-11-(pyrrol-3-yl)undecan-2-yl acetate (31): syrup; R_f=

Synthesis of 2-(10-Hydroxyundecyl)pyrrole (9), 2-(10-

Methoxyundecyl)pyrrole (49), 2-(10-(Benzyloxy)undecyl)-

pyrrole (50), and 2-(7-Hydroxyoctyl)pyrrole (51). Compounds

9 (262 mg, 65%), 49 (341 mg, 72%), 50 (359 mg, 75%), and 51 (260

mg, 67%) were synthesized by the same procedure as described for

[10′-d]-9.

1

2-(10-Hydroxyundecyl)pyrrole (9): compound 9 has the same

spectral data as shown for [10′S]-9.

0.25 (20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 9.52 (br

s, 1H), 7.43 (m, 1H), 6.77 (dd, J = 2.5, 4.9 Hz, 1H), 6.65 (dd, J = 2.5,

4.2 Hz, 1H), 4.88 (m, 1H), 2.75 (t, J = 7.4 Hz, 2H), 2.03 (s, 3H),

1.72−1.28 (m, 14H), 1.20 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100

MHz) δ 197.2, 171.0, 125.8, 123.4, 119.5, 108.6, 71.2, 39.7, 35.9, 29.4

(3C), 29.3, 25.4, 25.1, 21.4, 19.9; HRMS (ESI) calcd for C₁₇H₂₈NO₃

(M + H)⁺294.2064, found 294.2056; IR (KBr) ν_max3280, 2936, 2851,

1734, 1664, 1244 cm⁻¹.

2-(10-Methoxyundecyl)pyrrole (49): syrup; R_f= 0.65 (15% EtOAc/

hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 8.01 (br s, 1H), 6.68 (dd, J

= 2.8, 4.2 Hz, 1H), 6.15 (t, J = 2.8 Hz, 1H), 5.94 (m, 1H), 3.35 (s,

3H), 3.32 (m, 1H), 2.62 (t, J = 7.6 Hz, 2H), 1.66−1.51 (m, 3H),

1.38−1.31 (m, 13H), 1.15 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100

MHz) δ 132.9, 116.0, 108.2, 104.8, 76.9, 55.9, 36.4, 29.8, 29.7, 29.6,

29.5, 29.4 (2C), 27.7, 25.5, 19.0; HRMS (ESI) calcd for C₁₆H₃₀NO

(M + H)⁺252.2322, found 252.2327; IR (KBr) ν_max3297, 2935, 2853,

1693, 1464, 1373 cm⁻¹.

10-Methoxy-1-(pyrrol-2-yl)undecan-1-one (46a): syrup; R_f= 0.50

1

(20% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 10.02 (br s,

1H), 7.05 (m, 1H), 6.94 (m, 1H), 6.28 (m, 1H), 3.32 (s, 3H), 3.30 (m,

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Article

2-(10-(Benzyloxy)undecyl)pyrrole (50): syrup; R_f= 0.80 (15%

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 7.95 (br s, 1H),

11-(5-((5-Ethyl-4′-methoxy-[2,2′-bipyrrol]-5′-ylidene)methyl)-

pyrrol-2-yl)undecan-2-ol (36): mp 90−92 °C; R_f= 0.30 (50% EtOAc/

hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 6.80 (s, 1H), 6.56 (d, J = 3.5

Hz, 1H), 6.42 (d, J = 3.6 Hz, 1H), 6.06 (s, 1H), 5.82 (d, J = 3.5 Hz,

1H), 5.80 (d, J = 3.6 Hz, 1H), 3.96 (s, 3H), 3.81 (m, 1H), 2.16 (q, J =

7.5 Hz, 2H), 2.03 (q, J = 7.6 Hz, 2H), 1.47−1.12 (m, 19H), 0.91 (t, J =

7.6 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 169.2, 160.2, 144.5,

141.3, 138.5, 128.3, 127.1, 120.4, 114.9, 113.7, 108.2, 107.1, 95.8, 68.2,

58.4, 39.4, 29.7 (2C), 29.6 (2C), 29.4, 29.2, 27.1, 25.8, 23.5, 20.8, 13.4;

HRMS (ESI) calcd for C₂₇H₃₉N₃O₂(M + H)⁺438.3115, found

438.3105; IR (KBr) ν_max3429, 3129, 2929, 2848, 1618, 1576, 1402

cm⁻¹.

1

7.41−7.31 (m, 5H), 6.69 (m, 1H), 6.17 (dd, J = 2.8, 5.8 Hz, 1H), 5.96

(m, 1H), 4.61 (d, J = 11.8 Hz, 1H), 4.50 (d, J = 11.8 Hz, 1H), 3.55 (m,

1H), 2.63 (t, J = 7.6 Hz, 2H), 1.67−1.62 (m, 3H), 1.48−1.32 (m,

13H), 1.24 (d, J = 6.3 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 139.2,

132.9, 128.3 (2C), 127.7 (2C), 127.4, 116.0, 108.2, 104.9, 75.0, 70.3,

36.7, 29.7 (2C), 29.6, 29.5 (2C), 29.4, 27.8, 25.6, 19.7; HRMS (ESI)

calcd for C₂₂H₃₄NO (M + H)⁺328.2635, found 328.2638; IR (KBr)

ν_max3280, 2934, 2847, 1682, 1404 cm⁻¹.

2-(7-Hydroxyoctyl)pyrrole (51): mp 80−82 °C; R_f= 0.42 (60%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 8.05 (br s, 1H), 6.65

(m, 1H), 6.13 (dd, J = 2.8, 5.6 Hz, 1H), 5.91 (br s, 1H), 3.80 (m, 1H),

2.59 (t, J = 7.6 Hz, 2H), 1.63 (m, 2H), 1.48−1.33 (m, 8H), 1.19 (d, J =

6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 132.7, 116.0, 108.1,

104.8, 68.1, 39.2, 29.6, 29.4, 29.3, 27.7, 25.6, 23.5; HRMS (ESI) calcd

for C₁₂H₂₁NaNO (M + Na)⁺218.1515, found 218.1509; IR (KBr)

ν_max3374, 2929, 2855, 1712, 1673, 1463, 1378 cm⁻¹.

11-(5-((5-(Furan-2-yl)-3-methoxypyrrol-2-ylidene)methyl)pyrrol-

2-yl)undecan-2-ol (37): mp 80−82 °C; R_f= 0.42 (60% EtOAc/

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 7.55 (d, J = 1.2 Hz, 1H),

6.97 (d, J = 3.3 Hz, 1H), 6.88 (s, 1H), 6.57 (d, J = 3.6 Hz, 1H), 6.54

(dd, J = 1.8, 3.4 Hz, 1H), 6.01 (d, J = 3.6 Hz, 1H), 5.98 (s, 1H), 3.88

(s, 3H), 3.78 (m, 1H), 2.72 (t, J = 7.5 Hz, 2H), 1.72 (m, 2H), 1.43−

1.33 (m, 14H), 1.19 (d, J = 6.2 Hz, 3H); ¹³C NMR (CDCl₃, 100

MHz) δ 168.1, 156.3, 151.4, 143.9, 143.6, 140.7, 129.9, 120.6, 118.1,

112.2, 110.5, 109.5, 94.8, 68.2, 58.3, 39.4, 29.6 (2C), 29.4 (2C), 29.3,

28.9, 28.4, 25.8, 23.5; HRMS (ESI) calcd for C₂₅H₃₅N₂O₃(M + H)⁺

411.2642, found 411.2625; IR (KBr) ν_max3420, 3120, 2929, 2852,

1615, 1574, 1497 cm⁻¹.

Synthesis of Prodiginines 2 and 32−38. Compounds 2 (110

mg, 68%), 32 (194 mg, 87%), 33 (199 mg, 76%), 34 (66 mg, 70%), 35

(70 mg, 65%), 36 (75 mg, 75%), 37 (66 mg, 71%), and 38 (74 mg,

71%) were synthesized by the same procedure as described for (23S)-

2.

23-Hydroxyundecylprodiginine (2): Compound 2 has the same

spectral data as shown for [23S]-2.

11-(5-((4′-Methoxy-1-methyl-[2,2′-bipyrrol]-5′-ylidene)methyl)-

pyrrol-2-yl)undecan-2-ol (38): mp 78−80 °C; R_f= 0.40 (60% EtOAc/

23-Methoxyundecylprodiginine (32): syrup; R_f= 0.55 (40%

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 6.80 (d, J = 2.6 Hz, 1H),

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 6.88 (s, 1H), 6.69

6.76 (s, 1H), 6.70 (dd, J = 1.5, 3.8 Hz, 1H), 6.49 (d, J = 3.6 Hz, 1H),

6.21 (dd, J = 2.6, 3.8 Hz, 1H), 5.98 (d, J = 3.6 Hz, 1H), 5.91 (s, 1H),

4.17 (s, 3H), 3.88 (s, 3H), 3.76 (m, 1H), 2.65 (t, J = 7.5 Hz, 2H), 1.42

(m, 2H), 1.39−1.25 (m, 14H), 1.18 (d, J = 6.2 Hz, 3H); ¹³C NMR

(CDCl₃, 100 MHz) δ 167.4, 159.4, 141.8, 140.9, 129.9, 128.8, 128.2,

118.2, 115.0, 114.7, 108.8, 108.5, 96.6, 68.2, 58.3, 39.4, 37.7, 29.6 (2C),

29.5, 29.4, 29.3, 29.2, 28.5, 25.8, 23.5; HRMS (ESI) calcd for

C₂₆H₃₈N₃O₂(M + H)⁺424.2959, found 424.2941; IR (KBr) ν_max

3422, 3128, 2928, 2852, 1623, 1574, cm⁻¹.

(dd, J = 1.3, 3.6 Hz, 1H), 6.63 (dd, J = 1.3, 2.6 Hz, 1H), 6.47 (d, J =

3.6 Hz, 1H), 6.14 (dd, J = 2.6, 3.6 Hz, 1H), 6.13 (s, 1H), 5.85 (d, J =

3.6 Hz, 1H), 4.00 (s, 3H), 3.35 (s, 3H), 3.32 (m, 1H), 2.07 (t, J = 7.4

Hz, 2H), 1.50 (m, 1H), 1.39−1.22 (m, 15H), 1.17 (d, J = 6.2 Hz, 3H);

¹³C NMR (CDCl₃, 100 MHz) δ 169.1, 160.3, 144.7, 138.6, 128.4,

128.3, 123.0, 121.0, 116.0, 112.8, 110.0, 108.6, 95.7, 76.9, 58.4, 56.0,

36.4, 29.8, 29.7, 29.6 (2C), 29.4, 29.2, 27.3, 25.5, 19.1; HRMS (ESI)

calcd for C₂₆H₃₈N₃O₂(M + H)⁺424.2958, found 424.2959; IR (KBr)

ν_max3318, 2926, 2853, 1625, 1362 cm⁻¹.

23-Benzoxyundecylprodiginine (33): syrup; R_f= 0.40 (30%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 7.40−7.30 (m,

5H), 6.90 (s, 1H), 6.71 (dd, J = 1.2, 3.6 Hz, 1H), 6.65 (dd, J = 1.2, 2.3

Hz, 1H), 6.50 (d, J = 3.7 Hz, 1H), 6.15 (dd, J = 2.5, 3.6 Hz, 1H), 6.12

(s, 1H), 5.86 (d, J = 3.7 Hz, 1H), 4.62 (d, J = 11.8 Hz, 1H), 4.50 (d, J

= 11.8 Hz, 1H), 4.00 (s, 3H), 3.55 (m, 1H), 2.08 (t, J = 7.6 Hz, 2H),

1.67 (m, 1H), 1.49−1.16 (m, 18H); ¹³C NMR (CDCl₃, 100 MHz) δ

169.1, 160.3, 144.7, 139.2, 138.5, 128.4 (2C), 128.3 (2C), 127.6 (2C),

127.4, 123.0, 121.1, 116.1, 112.9, 110.0, 108.6, 95.8, 75.0, 70.3, 58.4,

36.8, 29.8, 29.7, 29.6 (2C), 29.4, 29.2, 27.3, 25.6, 19.7; HRMS (ESI)

calcd for C₃₂H₄₂N₃O₂(M + H)⁺500.3272, found 500.3271; IR (KBr)

ν_max3321, 2931, 2845, 1617 cm⁻¹.

Synthesis of 54a−c. Compounds 54a (2.30 g, 94%), 54b (2.32 g,

96%), and 54c (2.29 g, 96%) were synthesized by the same procedure

as described for [10-d]-29.

10-Acetoxydecanoic acid (54a): semisolid, R_f= 0.45 (40% EtOAc/

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 4.02 (t, J = 6.7 Hz, 2H),

2.31 (t, J = 7.5 Hz, 2H), 2.01 (s, 3H), 1.60 (m, 4H), 1.27 (m, 10H);

¹³C NMR (CDCl₃, 100 MHz) δ 179.9, 171.4, 64.7, 34.0, 29.2, 29.1

(2C), 29.0, 28.5, 25.8, 24.6, 21.0; HRMS (ESI) calcd for C₁₂H₂₂NaO₄

(M + Na)⁺253.1410, found 253.1403; IR (KBr) ν_max2916, 2848,

1731, 1689, 1256, cm⁻¹.

11-Acetoxyundecanoic acid (54b): mp 35−37 °C; R_f= 0.50 (40%

1

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 4.02 (t, J = 6.7 Hz,

2H), 2.32 (t, J = 7.5 Hz, 2H), 2.02 (s, 3H), 1.58 (m, 4H), 1.28 (m,

12H); ¹³C NMR (CDCl₃, 100 MHz) δ 180.0, 171.4, 64.7, 34.1, 29.4,

29.3, 29.2 (2C), 29.0, 28.6, 25.9, 24.6, 21.0; HRMS (ESI) calcd for

C₁₃H₂₄NaO₄(M + Na)⁺267.1567, found 267.1559; IR (KBr) ν_max

2920, 2846, 1728, 1679 cm⁻¹.

12-Acetoxydodecanoic acid (54c): mp 40−42 °C; R_f= 0.55 (40%

EtOAc/hexanes);¹H NMR (CDCl₃, 400 MHz) δ 4.02 (t, J = 6.7 Hz,

2H), 2.31 (t, J = 7.5 Hz, 2H), 2.02 (s, 3H), 1.58 (m, 4H), 1.28 (m,

14H); ¹³C NMR (CDCl₃, 100 MHz) δ 180.0, 171.4, 64.7, 34.1, 29.4

(3C), 29.3, 29.2, 29.0, 28.6, 25.9, 24.6, 21.0; HRMS (ESI) calcd for

C₁₄H₂₆NaO₄(M + Na)⁺281.1723, found 281.1718; IR (KBr) ν_max

2916, 2850, 1731, 1691, 1256 cm⁻¹.

20-Hydroxyoctylprodiginine (34): mp 88−90 °C; R_f= 0.35 (50%

1

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 6.86 (s, 1H), 6.68

(dd, J = 1.0, 3.5 Hz, 1H), 6.61 (d, J = 1.0 Hz, 1H), 6.47 (d, J = 3.7 Hz,

1H), 6.11 (dd, J = 2.6, 3.5 Hz, 1H), 6.09 (s, 1H), 5.82 (d, J = 3.7 Hz,

1H), 3.97 (s, 3H), 3.78 (m, 1H), 2.05 (t, J = 7.5 Hz, 2H), 1.44−1.28

(m, 13H); ¹³C NMR (CDCl₃, 100 MHz) δ 169.1, 160.3, 144.5, 138.6,

128.3 (2C), 123.0, 121.1, 116.0, 112.9, 110.0, 108.6, 95.8, 68.1, 58.4,

39.3, 29.4, 29.3, 29.1, 27.2, 25.7, 23.5; HRMS (ESI) calcd for

C₂₂H₃₀N₃O₂(M + H)⁺368.2333, found 368.2319; IR (KBr) ν_max

3418, 3125, 2929, 2847, 1622, 1575, 1490 cm⁻¹.

11-(5-((3′,4′-Dimethyl-[2,2′-bipyrrol]-5′-ylidene)methyl)pyrrol-2-

yl)undecan-2-ol hydrochloride (35): mp 119−121 °C; R_f= 0.35 (50%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 13.10 (s, 1H), 12.94

(s, 1H), 12.56 (s, 1H), 7.26 (s, 1H), 7.03 (d, J = 2.3 Hz, 1H), 6.83 (br

s, 2H), 6.37 (dd, J = 2.5, 3.6 Hz, 1H), 6.20 (d, J = 3.6 Hz, 1H), 3.77

(m, 1H), 2.94 (br s, 2H), 2.21 (s, 6H), 1.73 (m, 2H), 1.45−1.22 (m,

14H), 1.16 (d, J = 6.1 Hz, 3H); ¹³C NMR (CDCl₃, 100 MHz) δ 154.6,

147.5, 144.5, 130.6, 129.2, 129.0 (2C), 125.0, 122.1, 118.9, 118.2,

113.2, 112.0, 68.1, 39.4, 29.6, 29.5, 29.4 (2C), 29.3, 29.2, 28.5, 25.7,

23.5, 11.8, 10.2; HRMS (ESI) calcd for C₂₆H₃₈N₃O (M + H)⁺

408.3009, found 408.2997; IR (KBr) ν_max3397, 3146, 2925, 2855,

1620, 1592, 1400 cm⁻¹.

Synthesis of 55a−c and 56a−c. Compounds 55a (614 mg,

59%), 55b (601 mg, 55%), 55c (641 mg, 56%), 56a (73 mg, 7%), 56b

(87 mg, 8%), and 56c (114 mg, 10%) were synthesized by the same

procedure as described for [10′-d]-30 and [10′-d]-31.

10-Oxo-10-(pyrrol-2-yl)decyl acetate (55a): syrup; R_f= 0.52 (40%

1

EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 10.15 (br s, 1H),

7.03 (m, 1H), 6.91 (m, 1H), 6.24 (m, 1H), 4.02 (t, J = 6.8 Hz, 2H),

2.74 (t, J = 7.4 Hz, 2H), 2.02 (s, 3H), 1.71−1.55 (m, 4H), 1.28 (m,

10H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.5, 171.3, 132.0, 125.0,

116.6, 110.5, 64.6, 38.0, 29.4, 29.3 (2C), 29.2, 28.6, 25.9. 25.3, 21.0;

11686

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HRMS (ESI) calcd for C₁₆H₂₆NO₃(M + H)⁺280.1907, found

280.1902; IR (KBr) ν_max3283, 2929, 2856, 1739, 1639, 1404, 1240

cm⁻¹.

4H), 1.28 (m, 16H); ¹³C NMR (CDCl₃, 100 MHz) δ 132.9, 116.0,

108.1, 104.8, 63.0, 32.8, 29.7 (3C), 29.6 (2C), 29.5 (2C), 29.4, 27.7,

25.7; HRMS (ESI) calcd for C₁₆H₃₀NaNO (M + Na)⁺275.2220,

found 275.2209; IR (KBr) ν_max3362, 2928, 2853, 1564, 1402 cm⁻¹.

Synthesis of Podiginines 39−41. Compounds 39 (83 mg, 80%),

40 (85 g, 79%), and 41 (83 g, 75%) were synthesized by the same

procedure as described for (23S)-2.

11-Oxo-11-(pyrrol-2-yl)undecyl acetate (55b): mp 53−55 °C; R_f=

0.65 (30% EtOAc/hexanes);¹H NMR (CDCl₃, 400 MHz) δ 9.82 (br s,

1H), 7.02 (m, 1H), 6.90 (m, 1H), 6.25 (m, 1H), 4.04 (t, J = 6.6 Hz,

2H), 2.75 (t, J = 7.5 Hz, 2H), 2.03 (s, 3H), 1.70 (m, 2H), 1.60 (m,

2H), 1.27 (m, 12H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.3, 171.3,

132.0, 124.6, 116.2, 110.5, 64.7, 38.0, 29.4 (4C), 29.2, 28.6, 25.9. 25.3,

21.0; HRMS (ESI) calcd for C₁₇H₂₈NO₃(M + H)⁺294.2064, found

294.2057; IR (KBr) ν_max3353, 3113, 2930, 2914, 2849, 1716, 1651,

1403 cm⁻¹.

10-(5-((4′-Methoxy-[2,2′-bipyrrol]-5′-ylidene)methyl)pyrrol-2-yl)-

decan-1-ol (39): mp 118−120 °C; R_f= 0.35 (50% EtOAc/hexanes);

¹H NMR (CDCl₃, 400 MHz) δ 6.85 (s, 1H), 6.68 (dd, J = 1.3, 3.6 Hz,

1H), 6.62 (dd, J = 1.3, 2.6 Hz, 1H), 6.46 (d, J = 3.6 Hz, 1H), 6.12 (dd,

J = 2.6, 3.6 Hz, 1H), 6.11 (s, 1H), 5.82 (d, J = 3.6 Hz, 1H), 3.97 (s,

3H), 3.64 (t, J = 6.6 Hz, 2H), 2.06 (t, J = 7.7 Hz, 2H), 1.55 (m, 2H),

1.38−1.27 (m, 14H); ¹³C NMR (CDCl₃, 100 MHz) δ 169.1, 160.2,

144.6, 138.6, 128.4, 128.3 123.0, 121.0, 116.0, 112.8, 110.0, 108.6, 95.7,

63.0, 58.4, 32.8, 29.6 (2C), 29.5 (2C), 29.3, 29.2, 27.3, 25.8; HRMS

(ESI) calcd for C₂₄H₃₄N₃O₂(M + H)⁺396.2646, found 396.2634; IR

(KBr) ν_max3367, 3124, 2912, 2846, 1630, 1578, 1490 cm⁻¹.

12-Oxo-12-(pyrrol-2-yl)dodecyl acetate (55c): mp 42−44 °C; R_f=

0.55 (35% EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 10.14 (br

s, 1H), 7.02 (m, 1H), 6.90 (m, 1H), 6.24 (m, 1H), 4.03 (t, J = 6.6 Hz,

2H), 2.74 (t, J = 7.5 Hz, 2H), 2.02 (s, 3H), 1.70 (m, 2H), 1.59 (m,

2H), 1.28 (m, 14H); ¹³C NMR (CDCl₃, 100 MHz) δ 191.4, 171.2,

132.0, 124.9, 116.4, 110.4, 64.6, 38.0, 29.4 (5C), 29.2, 28.5, 25.9. 25.3,

21.0; HRMS (ESI) calcd for C₁₈H₃₀NO₃(M + H)⁺308.2220, found

308.2214; IR (KBr) ν_max3349, 2912, 2850, 1714, 1644, 1405 cm⁻¹.

10-Oxo-10-(pyrrol-3-yl)decyl acetate (56a): syrup; R_f= 0.25 (40%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 9.53 (br s, 1H), 7.40

(dd, J = 1.5, 2.8 Hz, 1H), 6.74 (m, 1H), 6.62 (m, 1H), 4.02 (t, J = 6.8

Hz, 2H), 2.72 (t, J = 7.5 Hz, 2H), 2.02 (s, 3H), 1.71−1.56 (m, 4H),

1.27 (m, 10H); ¹³C NMR (CDCl₃, 100 MHz) δ 197.2, 171.4, 125.7,

123.3, 119.5, 108.5, 64.6, 39.7, 29.4, 29.3 (2C), 29.1, 28.5, 25.8, 25.1,

21.0; HRMS (ESI) calcd for C₁₆H₂₆NO₃(M + H)⁺280.1907, found

280.1905; IR (KBr) ν_max3279, 2928, 2848, 1566, 1472, 1400 cm⁻¹.

11-Oxo-11-(pyrrol-3-yl)undecyl acetate (56b): mp 39−41 °C; R_f=

0.32 (30% EtOAc/hexanes);¹H NMR (CDCl₃, 400 MHz) δ 9.45 (br s,

1H), 7.41 (m, 1H), 6.75 (dd, J = 2.3, 4.9 Hz, 1H), 6.63 (m, 1H), 4.03

(t, J = 6.6 Hz, 2H), 2.73 (t, J = 7.6 Hz, 2H), 2.02 (s, 3H), 1.69 (m,

2H), 1.59 (m, 2H), 1.28 (m, 12H); ¹³C NMR (CDCl₃, 100 MHz) δ

197.2, 171.4, 125.8, 123.3, 119.5, 108.6, 64.7, 39.7, 29.4 (3C), 29.3,

29.2, 28.5, 25.8, 25.1, 21.0; HRMS (ESI) calcd for C₁₇H₂₈NO₃(M +

H)⁺294.2064, found 294.2056; IR (KBr) ν_max3353, 3115, 2915, 2853,

1720, 1664, 1401 cm⁻¹.

11-(5-((4′-Methoxy-[2,2′-bipyrrol]-5′-ylidene)methyl)pyrrol-2-yl)-

undecan-1-ol (40): mp 108−110 °C; R_f= 0.35 (50% EtOAc/

1

hexanes); H NMR (CDCl₃, 400 MHz) δ 6.86 (s, 1H), 6.67 (dd, J =

1.0, 3.5 Hz, 1H), 6.61 (br s, 1H), 6.47 (d, J = 3.6 Hz, 1H), 6.12 (dd, J

= 2.7, 3.5 Hz, 1H), 6.08 (s, 1H), 5.82 (d, J = 3.6 Hz, 1H), 3.97 (s, 3H),

3.64 (t, J = 6.6 Hz, 2H), 2.05 (t, J = 7.6 Hz, 2H), 1.57 (m, 2H), 1.37−

1.15 (m, 16H); ¹³C NMR (CDCl₃, 100 MHz) δ 169.1, 160.3, 144.7,

138.6, 128.4, 128.3 123.0, 121.1, 116.0, 112.9, 110.0, 108.6, 95.8, 63.0,

58.4, 32.8, 29.7 (3C), 29.6, 29.5, 29.4, 29.2, 27.3, 25.8; HRMS (ESI)

calcd for C₂₅H₃₆N₃O₂(M + H)⁺410.2802, found 410.2793; IR (KBr)

ν_max3410, 3134, 2920, 2847, 1631, 1566, 1401 cm⁻¹.

12-(5-((4′-Methoxy-[2,2′-bipyrrol]-5′-ylidene)methyl)pyrrol-2-yl)-

dodecan-1-ol (41): mp 121−123 °C; R_f= 0.25 (50% EtOAc/

hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 6.85 (s, 1H), 6.66 (m, 1H),

6.62 (br s, 1H), 6.46 (d, J = 3.7 Hz, 1H), 6.12 (m, 1H), 6.08 (s, 1H),

5.82 (d, J = 3.7 Hz, 1H), 3.97 (s, 3H), 3.64 (t, J = 6.6 Hz, 2H), 2.07 (t,

J = 7.6 Hz, 2H), 1.57 (m, 2H), 1.35−1.16 (m, 18H); ¹³C NMR

(CDCl₃, 100 MHz) δ 169.1, 160.2, 144.6, 138.6, 128.4, 128.3 122.9,

121.0, 116.0, 112.8, 110.0, 108.6, 95.7, 63.1, 58.4, 32.8, 29.6 (5C), 29.5,

29.4, 29.2, 27.3, 25.8; HRMS (ESI) calcd for C₂₆H₃₈N₃O₂(M + H)⁺

424.2959, found 424.2948; IR (KBr) ν_max3397, 3123, 2915, 2848,

1634, 1580, 1489 cm⁻¹.

Bacterial Strains, Plasmids, and Cosmid. S. venezuelae ATCC

15439 was used as a heterologous host for marG overexpression.¹⁴

Escherichia coli One Shot Top10 (Invitrogen) was used as a host strain

for the construction of recombinant plasmids. E. coli ET12567

(pUZ8002) was used as donor strain in conjugation experiments.²⁹

pCR8-GW-TOPO (Invitrogen) was used as cloning vector. pSE34 is a

E. coli-Streptomyces shuttle vector, which contains pIJ101 derivative

replication element and the constitutive strong ermE* promoter.

pIJ778 is a plasmid containing an OriT transfer element required for

conjugation and the spectinomycin-resistant gene aadA. All bacterial

strains, plasmids, and cosmid used in this study are given in Table S1

(Supporting Information).

General DNA Manipulations. 8A7, a SuperCosl cosmid carrying

the entire mar gene cluster, was isolated by the standard protocol.^14,30

DNA fragments were recovered from an agarose gel by using the

QIAquick Gel Extraction Kit (QIAGEN). Restriction endonucleases

were purchased from New England Biolab. Preparation of plasmid

DNA was done by using a QIAprep Spin Miniprep Kit (QIAGEN). All

other DNA manipulations were performed according to standard

protocols.^30,31PCR was performed in 35 cycles by using a GeneAmp

PCR system 2700 (Applied Biosystems). Platinum Taq DNA

polymerase high ﬁdelity (Invitrogen) was used for ampliﬁcation of

marG gene. Oligodeoxyribonucleotides for PCR primers were

synthesized by Integrated DNA Technologies, and their sequences

are shown in Table S2 (Supporting Information). The nucleotide

sequences of the gene fragment were determined at the MMI DNA

analysis core facility, Oregon Health and Sciences University

(Portland, OR, USA).

12-Oxo-12-(pyrrol-3-yl)dodecyl acetate (56c): mp 44−46 °C; R_f=

1

0.30 (35% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 9.31 (br

s, 1H), 7.42 (m, 1H), 6.75 (dd, J = 2.3, 4.9 Hz, 1H), 6.64 (m, 1H),

4.03 (t, J = 6.6 Hz, 2H), 2.73 (t, J = 7.6 Hz, 2H), 2.03 (s, 3H), 1.69

(m, 2H), 1.59 (m, 2H), 1.28 (m, 14H); ¹³C NMR (CDCl₃, 100 MHz)

δ 197.4, 171.4, 125.9, 123.2, 119.5, 108.7, 64.7, 39.8, 29.5 (5C), 29.2,

28.6, 25.9, 25.1, 21.0; HRMS (ESI) calcd for C₁₈H₃₀NO₃(M + H)⁺

308.2220, found 308.2218; IR (KBr) ν_max3338, 2920, 2846, 1718,

1657, 1401 cm⁻¹.

Synthesis of 57a−c. Compounds 57a (287 mg, 72%), 57b (283

mg, 70%), and 57c (314 mg, 77%) were synthesized by the same

procedure as described for [10′-d]-9.

2-(10-Hydroxydecyl)pyrrole (57a): mp 57−59 °C; R_f= 0.50 (40%

EtOAc/hexanes); ¹H NMR (CDCl₃, 400 MHz) δ 8.05 (br s, 1H), 6.64

(m, 1H), 6.14 (dd, J = 2.8, 5.7 Hz, 1H), 5.92 (m, 1H), 3.64 (t, J = 6.6

Hz, 2H), 2.59 (t, J = 7.6 Hz, 2H), 1.64−1.54 (m, 4H), 1.33 (m, 12H);

¹³C NMR (CDCl₃, 100 MHz) δ 132.9, 116.0, 108.1, 104.7, 63.0, 32.7,

29.6, 29.5, 29.4 (2C), 29.3 (2C), 27.7, 25.7; HRMS (ESI) calcd for

C₁₄H₂₆NaNO (M + Na)⁺247.1907, found 247.1916; IR (KBr) ν_max

3356, 2928, 2848, 1566, 1472, 1400 cm⁻¹.

2-(11-Hydroxyundecyl)pyrrole (57b): mp 63−65 °C; R_f= 0.60

1

(30% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 8.07 (br s,

1H), 6.66 (dd, J = 2.6, 4.1 Hz, 1H), 6.14 (dd, J = 2.8, 5.7 Hz, 1H), 5.92

(d, J = 1.0 Hz 1H), 3.64 (t, J = 6.5 Hz, 2H), 2.60 (t, J = 7.6 Hz, 2H),

1.65−1.54 (m, 4H), 1.33 (m, 14H); ¹³C NMR (CDCl₃, 100 MHz) δ

132.9, 115.9, 108.1, 104.7, 62.9, 32.7, 29.6, 29.5 (3C), 29.4 (2C), 29.3,

27.7, 25.7; HRMS (ESI) calcd for C₁₅H₂₈NaNO (M + Na)⁺261.2063,

found 261.2055; IR (KBr) ν_max3355, 3147, 2930, 2847, 1566, 1400

cm⁻¹.

2-(12-Hydroxydodecyl)pyrrole (57c): mp 69−71 °C; R_f= 0.65

1

(30% EtOAc/hexanes); H NMR (CDCl₃, 400 MHz) δ 8.02 (br s,

1H), 6.66 (m, 1H), 6.13 (dd, J = 2.8, 5.8 Hz, 1H), 5.92 (d, J = 0.7 Hz

1H), 3.64 (t, J = 6.5 Hz, 2H), 2.59 (t, J = 7.6 Hz, 2H), 1.66−1.54 (m,

Generation of marG Overexpression Strain. The marG ORF

was ampliﬁed using forward primer marG-15bF, introducing a unique

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The Journal of Organic Chemistry

Article

NdeI site at the 5′-end of the gene, and the reverse primer marG-

15bR, introducing a unique BamHI site downstream to the TGA

translational stop codon. Cosmid DNA 8A7 was used as a template.

The PCR fragment was ﬁrst cloned into the pCR8-GW-TOPO vector.

The 1.4-kbp NdeI-BamHI insert was further subcloned into pET15b

to generate pMarG-15b. After sequencing to conﬁrm the inset, this

plasmid was digested with XbaI and HindIII. The fragment containing

the marG gene, along with the ribosome binding site (RBS), was

cloned into the corresponding sites of pSE34 to generate pMarG-34.

The ampicillin resistance marker bla on the pMarG-34 plasmid was

replaced by aadA-oriT cassette generated by PCR from pIJ778 with

primers Amp-SpF/Amp-SpR using the standard method of PCR

targeting.³²The resulting pMarG-34S was introduced into S. venezuelae

strain by conjugation following the established protocol, except

mannitol-soy ﬂour agar was replaced with AS1 media containing 10

mM MgCl₂.³³Thiostrepton-resistant exconjugants representing S.

venezuelae strains host with marG overexpression plasmids. The new

strain was named S. venezuelae MarG.

Media, Culture Techniques, and Feeding Experiments.

Recombinant S. venezuelae MarG was grown on sporulation agar

(SPA; 0.1% yeast extract, 0.1% beef extract, 0.2% tryptose, 0.01%

ferrous sulfate, 1.0% glucose, and 2.0% Difco bacto agar) containing 50

μg/mL of spectinomycin at 30 °C for 7 days. Fresh spores were used

to inoculate 10 mL of SCM seed cultures (1.5% soluble starch, 2.0%

soytone, 0.01% CaCl₂, 0.15% yeast extract and 1.0% MOPS, pH 7.2)

containing 10 μg/mL of spectinomycin and were incubated at 30 °C

for 3 days. Production cultures were prepared with the same medium

(150 mL each ﬂask) and inoculated with seed cultures (5.0% v/v). The

production cultures were grown in Baﬄed Erlenmeyer ﬂasks at 30 °C

with vigorous shaking (220 rpm). After incubation for 3 days, the

cultures were grouped into four groups; the ﬁrst group was fed with

(23S)-2 (2.0 mg in 200 μL of DMSO), the second group was fed with

[23-d]-2 (2.0 mg in 200 μL of DMSO), the third group was fed with 3

(2.0 mg in 200 μL of DMSO), and the fourth group (control group)

was fed with 200 μL of DMSO. After 4 days of incubation, the cultures

were harvested by centrifugation at 5000 rpm, 4 °C for 20 min. The

harvested cells were disrupted by the addition of 20 mL of methanol

solution containing 1.0% 2 N HCl followed by vortex for 1 min. After

ﬁltration using cotton wool, the methanol extract was dried under

reduced pressure and stored at −20 °C until further analysis. The same

procedures were used for other analogues.

Notes

The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

This work was supported by a grant from the National

Institutes for Health (GM077147).

REFERENCES

(1) Furstner, A. Angew. Chem., Int. Ed. 2003, 42, 3582−3603.

(2) (a) Boger, D. L.; Patel, M. J. J. Org. Chem. 1988, 53, 1405−1415.

(b) Alihosseini, F.; Ju, K. S.; Lango, J.; Hammock, B. D.; Sun, G.

Biotechnol. Prog. 2008, 24, 742−747. (c) Marchal, E.; Uddin, M. I.;

Smithen, D. A.; Hawco, C. L. A.; Lanteigne, M.; Overy, D. P.; Kerr, R.

G.; Thompson, A. RSC Adv. 2013, 3, 22967−22971.

■

̈

(3) (a) Nakamura, A.; Nagai, K.; Ando, K.; Tamura, G. J. Antibiot.

1985, 39, 1155−1159. (b) Tsuji, R. F.; Yamamoto, M.; Nakamura, A.;

Katoka, T.; Magae, J.; Nagai, K.; Jamasaki, M. J. Antibiot. 1990, 43,

1293−1301. (c) Magae, J.; Miller, J. W.; Nagai, K.; Shearer, G. M. J.

Antibiot. 1996, 49, 86−90. (d) D’Alessio, R.; Bargiotti, A.; Carlini, O.;

Colotta, F.; Ferrari, M.; Gnocchi, P.; Isetta, A.; Mongelli, N.; Motta, P.;

Rossi, A.; Rossi, M.; Tibolla, M.; Vanotti, E. J. Med. Chem. 2000, 43,

2557−2565. (e) Han, S. B.; Kim, H. M.; Kim, Y. H.; Lee, C. W.; Jang,

E. S.; Son, K. H.; Kim, S. U.; Kim, Y. K. Int. J. Immunopharmacol. 1998,

20, 1−13.

(4) Williams, R. P.; Hearn, W. R. Antibiotics 1967, 2, 410−432; 1967,

2, 449−451.

(5) (a) Perez-Tomas, R.; Montaner, B.; Llagostera, E.; Soto-Cerrato,

́ ́

V. Biochem. Pharmacol. 2003, 66, 1447−1452. (b) Regourd, J.; Al-

Sheikh Ali, A.; Thompson, A. J. Med. Chem. 2007, 50, 1528−1536.

(c) Sessler, J. L.; Eller, L. R.; Cho, W.-S.; Nicolaou, S.; Aguilar, A.; Lee,

J. T.; Lynch, V. M.; Magda, D. J. Angew. Chem., Int. Ed. 2005, 44,

5989−5992. (d) Marchal, E.; Rastogi, S.; Thompson, A.; Davis, J. T.

́

Org. Biomol. Chem. 2014, 12, 7515−7522. (e) Dıaz de Grenu, B.;

̃

Hernan

́

dez, P. I.; Espona, M.; Quinonero, D.; Light, M. E.; Torroba,

̃

T.; Perez-Tomas, R.; Quesada, R. Chem. Eur. J. 2011, 17, 14074−

́

14083. (f) Hawco, C. L. A.; Marchal, E.; Uddin, M. I.; Baker, A. E. G.;

Corkery, D. P.; Dellaire, G.; Thompson, A. Bioorg. Med. Chem. 2013,

21, 5995−6002. (g) Smithen, D. A.; Forrester, A. M.; Corkery, D. P.;

Dellaire, G.; Colpitts, J.; McFarland, S. A.; Berman, J. N.; Thompson,

A. Org. Biomol. Chem. 2013, 11, 62−68.

Premarineosin Production Analysis. The crude methanolic

extract was dissolved in methanol, centrifuged, and ﬁltered through a

0.22 μm ﬁlter to give a clear solution, and this was used for our

analysis. Analytical HPLC and LC-MS analyses were performed on a

C18 column (2.1 mm × 250 mm, 5 μm) with a linear elution gradient

as speciﬁed in Table S4 (Supporting Information). The molecular

weight of each compound was determined by electrospray mass

spectrometry. Extracted ion chromatograms and tandem MS analyses

were performed to analyze the consumption of feeding substrates and

the production of premarineosins.

(6) (a) Castro, A. J. Nature 1967, 213, 903−904. (b) Gerber, N. N. J.

Antibiot. 1975, 28, 194−199. (c) Davidson, D. E., Jr.; Johnsen, D. O.;

Tanticharoenyos, P.; Hickman, R. L.; Kinnamon, K. E. Am. J. Trop.

Med. Hyg. 1976, 25, 26−33. (d) Isaka, M.; Jaturapat, A.; Kramyu, J.;

Tanticharoen, M.; Thebtaranonth, Y. Antimicrob. Agents Chemother.

2002, 46, 1112−1113. (e) Lazaro, J. E. H.; Nitcheu, J.; Predicala, R. Z.;

Mangalindan, G. C.; Nesslany, F.; Marzin, D.; Concepcion, G. P.;

Diquet, B. J. Nat. Toxins 2002, 11, 367−377. (f) Marchal, E.; Smithen,

D. A.; M. Uddin, I.; Robertson, A. W.; Jakeman, D. L.; Mollard, V.;

Goodman, C. D.; MacDougall, K. S.; McFarland, S. A.; McFadden, G.

I.; Thompson, A. Org. Biomol. Chem. 2014, 12, 4132−4142.

(7) Papireddy, K.; Smilkstein, M.; Kelly, J. X.; Shweta; Salem, S. M.;

Alhamadsheh, M.; Haynes, S. W.; Challis, G. L.; Reynolds, K. A. J.

Med. Chem. 2011, 54, 5296−5306.

(8) (a) Saes Dias, R. I.; Regourd, J.; Santacroce, P. V.; Davis, J. T.;

Jakeman, D. L.; Thompson, A. Chem. Commun. 2007, 2701−2703.

(b) Seganish, J. L.; Davis, J. T. Chem. Commun. 2005, 5781−5783.

(c) Melvin, M. S.; Tomlinson, J. T.; Park, G.; Day, C. S.; Saluta, G. S.;

Kucera, G. L.; Manderville, R. A. Chem. Res. Toxicol. 2002, 15, 734−

741. (d) Matsuya, H.; Okamoto, M.; Ochi, T.; Nishikawa, A.; Shimizu,

S.; Kataoka, T.; Nagai, K.; Wasserman, H. H.; Ohkuma, S. Biochem. J.

1998, 334, 731−741. (e) Gale, P. A.; Light, M. E.; McNally, B.;

Navakhun, K.; Sliwinski, K. E.; Smith, B. D. Chem. Commun. 2005,

3773−3775. (f) Davis, J. T.; Gale, P. A.; Okunola, O. A.; Prados, P.;

Iglesias-Sanchez, J. C.; Torroba, T.; Quesada, R. Nat. Chem. 2009, 1,

138−144. (g) Rastogi, S.; Marchal, E.; Uddin, I.; Groves, B.; Colpitts,

J.; McFarland, S. A.; Davis, J.T.; Thompson, A. Org. Biomol. Chem.

2013, 11, 3834−3845.

ASSOCIATED CONTENT

■

S

* Supporting Information

Figures giving spectra of all synthesized compounds, tables

giving cosmids, strains, and primers, and ﬁgures giving HPLC,

MS, MS/MS, and LC-MS proﬁles. This material is available free

of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION

■

Corresponding Author

*K.A.R.: mailing address, Finance & Administration, Portland

State University, P.O. Box 751, Portland, Oregon, 97207-0751;

tel, 503 725 3886; fax, 503 725 5800; e-mail, reynoldk@pdx.

edu.

Author Contributions

^‡These authors contributed equally to this work.

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(9) Melvin, M. S.; Ferguson, D. C.; Lindquist, N.; Manderville, R. A.

J. Org. Chem. 1999, 64, 6861−6869.

(10) Borthakur, G.; O’Brien, S.; Ravandi-Kashani, F.; Giles, F.;

Schimmer, A. D.; Viallet, J.; Kantarjian, H. Blood 2006, 108, 750.

(11) Nguyen, M.; Marcellus, R. C.; Roulston, A.; Watson, M.; Serfass,

(33) Sioud, S.; Aigle, B.; Karray-Rebai, I.; Smaoui, S.; Bejar, S.;

Mellouli, L. J. Biomed. Biotechnol. 2009, 2009, 464986.

́

L.; Madiraju, S. R. M.; Goulet, D.; Viallet, J.; Belec, L.; Billot, X.;

Acoca, S.; Purisima, E.; Wiegmans, A.; Cluse, L.; Johnstone, R. W.;

Beauparlant, P.; Shore, G. C. Proc. Natl. Acad. Sci. U.S.A. 2007, 104,

19512−19517.

(12) Kancharla, P.; Reynolds, K. A. Tetrahedron 2013, 69, 8375−

8385.

(13) Boonlarppraadab, C.; Kauffman, C. A.; Jensen, P. R.; Fenical, W.

Org. Lett. 2008, 10, 5505−5508.

(14) Salem, S. M.; Kancharla, P.; Florova, G.; Gupta, S.; Lu, W.;

Reynolds, K. A. J. Am. Chem. Soc. 2014, 136, 4565−4574.

(15) (a) Cai, X. C.; Wu, X.; Snider, B. B. Org. Lett. 2010, 12, 1600−

1603. (b) Cai, X. C.; Snider, B. B. J. Org. Chem. 2013, 78, 12161−

12175. (c) Aldrich, L. N.; Dawson, E. S.; Lindsley, C. W. Org. Lett.

2010, 12, 1048−1051. (d) Panarese, J. D.; Konkol, L. C.; Berry, C. B.;

Bates, B. S.; Aldrich, L. N.; Lindsley, C. W. Tetrahedron Lett. 2013, 54,

2231−2234. (e) Aldrich, L. N.; Berry, C. B.; Bates, B. S.; Konkol, L.

C.; So, M.; Lindsley, C. W. Eur. J. Org. Chem. 2013, 4215−4218. (f) Li,

G.; Zhang, X.; Li, Q.; Feng, P.; Shi, Y. Org. Biomol. Chem. 2013, 11,

2936−2938.

(16) Haynes, S. W.; Sydor, P. K.; Stanley, A. E.; Song, L.; Challis, G.

L. Chem. Commun. 2008, 1865−1867.

(17) Sydor, P. K.; Barry, S. M.; Odulate, O. M.; Barona-Gomez, F.;

Haynes, S. W.; Corre, C.; Song, L.; Challis, G. L. Nat. Chem. 2011, 3,

388−392.

(18) Sydor, P. K.; Challis, G. L. Methods Enzymol. 2012, 516, 195−

218.

(19) Dairi, K.; Tripathy, S.; Attardo, G.; Lavallee, J.-F. Tetrahedron

Lett. 2006, 47, 2605−2606.

(20) Kakushima, M.; Hamel, P.; Frenette, R.; Rokach, J. J. Org. Chem.

1983, 48, 3214−3219.

(21) Choi, M.-Y.; Khaskin, G.; Gries, R.; Gries, G.; Roitberg, B. D.;

Raworth, D. A.; Kim, D.-H.; Bennett, R. G. J. Chem. Ecol. 2004, 30,

659−670.

(22) Howard, J. K.; Hyland, C. J. T.; Just, J.; Smith, J. A. Org. Lett.

2013, 15, 1714−1717.

(23) Alvi, K. A.; Casey, A.; Nair, B. G. J. Antibiot. 1998, 51, 515−517.

(24) Li, L.; Herzon, S. B. J. Am. Chem. Soc. 2012, 134, 17376−17379.

(25) Yadav, J. S.; Reddy, B. V. S.; Kondaji, G.; Rao, R. S.; Kumar, S.

P. Tetrahedron Lett. 2002, 43, 8133−8135.

(26) Greenhouse, R.; Ramirez, C.; Muchowski, J. M. J. Org. Chem.

1985, 50, 2961−2964.

(27) (a) Winter, R. W.; Kelly, J. X.; Smilkstein, M. J.; Dodean, R.;

Hinrichs, D.; Riscoe, M. K. Exp. Parasitol. 2008, 118, 487−497.

(b) Smilkstein, M.; Sriwilaijaroen, N.; Kelly, J. X.; Wilairat, P.; Riscoe,

M. Antimicrob. Agents Chemother. 2004, 48, 1803−1806. (c) Burgess,

S. J.; Selzer, A.; Kelly, J. X.; Smilkstein, M. J.; Riscoe, M. K.; Peyton, D.

H. J. Med. Chem. 2006, 49, 5623−5625. (d) Nilsen, A.; Miley, G. P.;

Forquer, I. P.; Mather, M. W.; Katneni, K.; Li, Y.; Pou, S.; Pershing, A.

M.; Stickles, A. M.; Ryan, E.; Kelly, J. X.; Doggett, J. S.; White, K. L.;

Hinrichs, D. J.; Winter, R. W.; Charman, S. A.; Zakharov, L. N.;

Bathurst, I.; Burrows, J. N.; Vaidya, A. B.; Riscoe, M. K. J. Med. Chem.

2014, 57, 3818−3834.

(28) Poon, K. W. C.; Dudley, G. B. J. Org. Chem. 2006, 71, 3923−

3927.

(29) Xue, Y.; Zhao, L.; Liu, H. W.; Sherman, D. H. Proc. Natl. Acad.

Sci. U.S.A. 1998, 95, 12111−12116.

(30) Kieser, T.; Bibb, M. J.; Buttner, M. J.; Chater, K. F.; Hopwood,

D. A. Practical Streptomyces Genetics; John Innes Foundation: Norwich,

England, 2000.

(31) Sambrook, J.; Russell, D. W. Molecular Cloning. A Laboratory

Manual, 3rd ed.; Cold Spring Harbor Laboratory Press: New York,

2001.

(32) Gust, B.; Challis, G. L.; Fowler, K.; Kieser, T.; Chater, K. F. Proc.

Natl. Acad. Sci. U.S.A. 2003, 100, 1541−1546.

11689

dx.doi.org/10.1021/jo5023553 | J. Org. Chem. 2014, 79, 11674−11689

Article Doi

Stereospecific synthesis of 23-hydroxyundecylprodiginines and analogues and conversion to antimalarial premarineosins via a Rieske oxygenase catalyzed bicyclization

DOI: 10.1021/jo5023553

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