The winding road of the uvaretin class of natural products: From total synthesis to bioactive agent discovery

Article abstract of DOI:10.1039/c9md00052f

Herein, we disclose the development of a synthetic route to gain access to the uvaretin class of chalcone natural products. In this, the construction of a small library was achieved, and the collection was evaluated for cytotoxicity and other biological properties. Uvaretin (1) was accessed via a seven-step route in an overall yield of 15.1%. Within this route, the unsaturated enone variant of uvaretin (2), also a natural product, was accessed in a 16.7% yield over six steps. This route provides a nearly three-fold increase in yields of 1 and 2 in comparison to the previous synthetic route accessing them in 5.8% and 3.0% overall yields, respectively. Evaluation of 1 and 2 revealed IC₅₀ values between 2.0 and 5.1 μM in the cancerous cell lines HeLa, U937, A549, and MIA PaCa-2. Screening of the whole chalcone library set led to the discovery of over 30 compounds, within six cancerous cell lines, possessing single digit μM IC₅₀ activity as sole agents. Furthermore, multiple library members were found to possess promising potentiating properties with known chemotherapeutic agents.

Full text of DOI:10.1039/c9md00052f

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DOI: 10.1039/C9MD00052F.
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The Winding Road of the Uvaretin Class of Natural Products: From Total
Synthesis to Bioactive Agent Discovery.
Johnathan Dallman‡, Ashabha Lansakara‡, Thi Nguyen‡, Chamitha Weeramange,
Wasundara Hulangamuwa, and Ryan J. Rafferty
Department of Chemistry, Kansas State University, 1212 Mid-Campus Drive North, Manhattan,
KS 66506
‡These authors contributed equally to the work
ABSTRACT
Herein, we disclose the development of a synthetic route to gain access to the uvaretin
class of chalcone natural products. In this, the construction of a small library was
achieved, and the collection was evaluated for cytotoxicity and other biological
properties. Uvaretin (1) was accessed via a seven-step route in an overall yield of
15.1%. Within this route, the unsaturated enone varient of uvaretin (2), also a natural
product, was accessed in a 16.7% yield over six steps. This route provides a nearly
three-fold increase in yields of 1 and 2 in comparison to the previous synthetic route
accessing them in 5.8% and 3.0% overall yields, respectively. Evaluation of 1 and 2
revealed IC50 values between 2.0 and 5.1 M in the cancerous cell lines HeLa, U937,
A549, and MIA PaCa-2. Screening of the whole chalcone library set led to the discovery
of over 30 compounds, within six cancerous cell lines, possessing single digit M IC50
activity as sole agents. Furthermore, multiple library members were found to possess
promising potentiating properties with known chemotherapeutic agents.

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1. Introduction
Chalcones, known for their classical ,-unsaturated ketone moiety flanked by phenyl
groups, are a central component to numerous natural products (Figure 1), such as, but
not limited to: butein, cardamonin, derricin, flavokawain, isoalipurposide, isoliquiritigenin,
licochalcone, naringenin, xanthohumol, xanthoangelol, and the uvaretin class.1 They
have been reported to possess wide encompassing biological properties including:
9
13
anticancer,2-7
antimalarial,8,
anti-inflammatory,10-13
antileishmanial,10,
antituberculotic,14 antimitotic,15 analgesic,16 antibacterial, and antifungal.17 There are
limited reports suggesting that they are also antimutagenic, antitumorigenic, and gastric
protectant.18 In addition to these properties, they are considered as the precursor of
flavonoids and isoflavonoids, which are highly abundant in edible plants.19
Figure 1 Chalcone core and the representative set of natural products containing said
core highlighted in green.
It has been shown that many chalcone containing natural products and synthetic
compounds elicit their biological effects through enone addition. In this, soft
nucleophiles such as thiols add into the  carbon of the enone. These properties make
the chalcone core biologically important, as hard nucleophiles, such as amines and
hydroxyl groups, both ubiquitous in biological system, will not add into chalcones. The

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mode of action of many chalcones arises from their interaction between multiple
proteins related to cell apoptosis and proliferation. The NF-B20-22 and Nrf2/ARE23, 24
pathways in which chalcones are reported to possess inhibitory properties within,
leading to their anti-inflammatory effects and induction of phase II detoxifying enzyme
expression.25
Our laboratory is interested in identifying new small molecules with interesting and
potent biological activity, such as anticancer. Either as sole agents or as potentiating
agents to be used alongside current prescribed therapeutics. In these efforts, we aim at
utilizing intermediates accessed within total synthesis campaigns, as well as failed
routes, for the assembly of small screening libraries. Noting the rich literature in
chalcone based compounds and their diverse biological activity, we choose to focus on
constructing a synthetic route that would be amendable for library construction for
uvaretin (1) and its analogous unsaturated enone (E)-1-(2,4-dihydroxy-3-(2-
hydroxybenzyl)-6-methoxyphenyl)-3-phenylprop-2-en-1-one (2) shown in Figure 2.
HO
OMe
HO
OMe
A
A
C
B
C
B
OH
OH
O
OH
OH
O
(E)-1-(2,4-dihydroxy-3-(2-hydroxybenzyl)-6-
methoxyphenyl)-3-phenylprop-2-en-1-one (2)
Cytotoxicity towards NCI-H187 lung, epidermoid
carcinoma, and breast cancer cell lines. Antimalarial
activity towards Plasmodium falciparum and
Mycobacterium tuberculosis reported.
Uvaretin (1): Inhibits the in
vitro growth of P-388
lymphocytic leukemia in mice
and nasopharynx carcinoma
cells in humans, and has
antibacterial properties.
Figure 2 Chalcone based natural products uravetin (1) and its unsaturated enone
analog (2).
Uvaretin (1) was first isolated in 1976 by Wiedhopf and Bates from the chloroform
extract of Uvaria acuminate Oliv (Annonaceae).26 Evaluation of 1 revealed activity in
vivo against P-388 lymphocytic leukemia in mice and in vitro activity against cells
derived from human carcinoma of the nasopharynx.27 In 2006, Suttisri and co-workers

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isolated 2, the unsaturated enone analog of 1, from the aerial part of Ellipeiopsis
cherrevenis (Annonaceae), which was found to possess cytotoxicity towards the human
small-cell lung cancer, epidermoid carcinoma, and breast cancer.28 The total synthesis
of 1, as well as 2 which was not isolated to date, was accomplished in 1985 by Malterud
and coworkers.29 Malterud’s route (Scheme 1) commenced with the condensation of
2,4-dihydroxy-6-methoxyacetophone
(3)30
and
2-hydroxyphenyl-bis-1,1-
piperidinomethane (4)31 accessing 5 in 60% yield. This step highlighted their key aminal
approach, previously disclosed by Kallay and co-workers.32, 33 Piperidine removal was
accomplished via hydrogenation in a variable 50-60% yield affording 6, the A/B ring
system. The attempts to perform the aldol condensation upon 6 to access 2 was
successful, albeit, in a 9% yield over 15 days. Hydrogenation of 2 afforded 1 in an
overall yield of 2.2% in 4-steps from the reported starting materials. Efforts to optimize
their route led to the benzyl protection of the phenolic groups, thought to have an
adverse effect in the aldol condenation, giving access to the dibenzylated 7a in 10%
yield and a mixture of the monobenzylated 7b/c in 21%. Aldol condensation upon 7a
and 7b/c gave access to the A/B/C core in 69% and 79% yields, respectively, and
hydrogenation to afford 1 in 74% and 73% yields, respectively. Through this new benzyl
protection route, 1 was accessed in an overall yield of 5.8% (combined yields of 7a and
7b/c) over five-steps from 3 (requiring three synthetic steps to acccess), and 4
(requiring one synthetic step to access).

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Scheme 1 Malterud’s total synthesis route to uvaretin.
While the route developed by Malterud provided access to both 1 and 2, it was the
late-stage installation of the chalcone core that led us to develop a new route to these
natural products. Given the desire to construct a new small library collection for
screening to identify new compounds with biological activity, early installation of the
chalcone core seemed more likely to achieve this task. Generally, synthesized natural
products and their relatively simple SAR analogs are evaluated for biological activity,
which generally failed to identify new small molecules with different bioactive properties.
Herein, we plan on screening all synthetic intermediates accessed in the efforts of
identifying new bioactive small molecules, in which the chalcone core will prove most
useful. Studies will be performed to identify new sole agent compounds, ones that have
potentiating properties with known therapeutics, and/or new small molecules with
interesting biological properties.
2. Results and Discussion
2.1 Synthesis
Efforts towards accessing the chalcone core early rather than late stage commenced
with construction of the B-ring. From phloroglucinol (8), the 2,4,6-trihydroxy-
acetophenone (9) was accessed through acylation with acetic anhydride in the

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presence of boron trifluoride etherate in 88% yield (Scheme 2).34 Treatment of 9 with
dimethyl sulfate in the presence of potassium carbonate in acetone afforded trimethoxy-
acetophenone (10) in 89% yield. Accessing 11 was accomplished through a potassium
hydroxide catalyzed aldol condensation between 10 and benzaldehyde in 81% yield.19
Scheme 2 Synthetic route to obtain the trimethylated chalone core.
Attention was then directed towards the installation of the western ortho-
hydroxybenzyl moiety (A-ring) via a Friedel-Craft alkylation approach. Construction of
the requisite material commenced with the allylation of ortho-hydroxybenzaldehyde (12)
with allyl bromide and potassium carbonate in dimethylformamide to access 13 in 95%
yield,35 which was then reduced with sodium borohydride in methanol to give access to
the desired, protected benzyl alcohol (14) in 72% yield (Scheme 3).36-38
Scheme 3 Constructed the required O-allyl benzyl alcohol for acylation attempts.
Next, efforts were directed towards the incorporation of 14 onto 11. The Lewis acid
mediated reaction between 11 and 14 proved to be more problematic than originally
anticipated (Scheme 4). Please see the supporting information for a detail table of all
conditions attempted. Two different Lewis acids were explored, boron trifluoride
etherate and ferric (III) chloride, in various solvents, temperatures, and orders of

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addition. It was originally thought that the use of an excess Lewis acid would facilitate
the formation of the benzyl carbocation of 14. This benzyl carbocation would
subsequently be attacked by 11 in a Friedel-Craft alkylation mechanism to afford 15 in
acceptable yields. However, the formation of 16 was observed in high yields. Finally, it
was found through utilizing the step-wise addition of boron trifluoride etherate in dioxane
in equal portions over a 10-minute period to a vigorously stirring solution of 11 and 14 in
dioxane, followed by heating at 60 C for 3 h led to a minimized yield of 16. The
formation of the uvaretin carbon core 15 was established in a 58% yield.
Scheme 4 Friedel-Crafts alkylation conditions gaining access to the uvaretin carbon
core.
Noting the importance of this alkylation step, efforts were taken to optimize the
reaction through modifications of the benzyl alcohol. It was speculated that the Lewis
acid activation of the benzyl alcohol tended to accelerate the formation of 16. To
suppress this, mesylate protection of the alcohol was performed with mesyl chloride to
afford 17 in 88% yield (Scheme 5). While this material was successfully transformed
onto 15, all conditions attempted failed to provided yields greater than 17%.
Transforming the benzyl alcohol into its chloride counterpart (18) was also performed in
92% yield, but failed to give 15 in yields above 20%. The addition of sodium iodide to
this reaction failed to provide any benefits in the formation of 15.

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MsCl, NEt3, THF, 88%
11
BF3•Et2O
MeO
OMe
OH
R
dioxane
OAllyl
OAllyl
14
17 (R = OMs)
18 (R = Cl)
OAllyl
OMe O
15
SOCl2, CHCl3, 92%
Scheme 5 Attempted optimization of the Friedel Crafts alkylation through employing
mesylate and chloride benzyl systems.
With the core skeleton of the uvaretin family in hand, the removal of the allyl group
and enone reduction were undertaken to validate the route as a feasible means of
accessing the carbon core of the uvaretin family of natural products. Subjecting 15 to
Pd(PPh3)4 and potassium carbonate in methanol successfully deprotected the allyl
group upon the western phenol to give access to 19 in 76% yield (Scheme 6).
Reduction of the enone was accomplished with H2 and 10% Pd/C in methanol to the
corresponding ketone 20 in 82% yield. With 20 in hand, the general route to the uvaretin
core has been established, allowing for the next steps in the construction of these
natural products.
Scheme 6 Allyl deprotection, construction of analogs 19 and 20, and attempts at
accessing natural products 1 and 2 via selective demethylation.
Acquiring both 19 and 20 led to efforts to explore if demethylation upon the B-ring
could be performed giving access to both 2 and uvaretin directly. Demethylation of
methoxy arenes is well precedented in the literature.29, 39-42 Illustrated within the insert of

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Scheme 6 highlights the use of aluminum chloride in the demethylation of 10 accessing
the di- and monomethylated acetophenone species. Employing the same conditions
upon 20 did afford uvaretin, albeit, in a 3% yield along with decomposed material.
Furthermore, the reaction did not consistently afford 1, and in most cases gave
decomposition only. Also, in multiple cases the debenzylated chalcone 21 was isolated,
which also had a single methyl group removed. The formation of 21 was not
consistently obtained; however, when it was obtained, the yields were less than 33%.
Attempting the same upon 19 afforded decomposition, however, one attempt did
provide a <1% yield of 2. Similar to 20, debenzylation of the A-ring was observed
affording 21 in yields no greater than 15%. It was suspected that the free phenol could
be affecting the demethylation, as such demethylation with AlCl3 was attempted upon
15. Unfortunately, only decomposition of the material was observed. The formation of
21 was not observed from 15, unlike from 19 and 20.
While both desired natural products, 1 and 2, were accessed in route described, we
were unsatisfied with the yields in the final step and decided to pursue demethylation
before the alkylation step. Treating chalcone 11 with aluminum chloride in
chlorobenzene afforded the dimethylated chalcone 21 in 68% yield (Scheme 7).
Concurrently, it was found that selective methylation, under equivalent control, of 9 gave
access to 22 in 86% yield. 22 was then subjected to potassium hydroxide mediated
aldol conditions to afford 21 in 99% yield, overall yield of 85% over two-steps.
Subjecting 21 to the alkylation conditions employed in Scheme 3, as well as the other
conditions presented in the SI, failed to afford 23. The isolation of the O-alkylated
compound was observed in numerous trials. As such, the free phenolic group within the

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B-ring was suspected to be the cause of this failed alkylation. Acetylation of this phenol
was attempted, followed by alkylation conditions to afford <5% of 23. Under these
conditions, deacetylation occurred rapidly which prevented the desired alkylation.
Protection of the phenol with a more robust protecting group was then explored.
Scheme 7 Attempted conditions at gaining accessing to the monophenol variant
chalcone.
Methoxymethyl ether (MOM) protecting group was chosen to protect the free phenol
given the strong literature precedence for its application in similar systems.1, 43-46
Subjecting 22 to MOMCl and potassium carbonate in acetone afforded the desired
protected material 24 in 85% yield, which was elaborated onto its corresponding
chalcone via the standard protocol to access 25 in 68% yield (Scheme 8). Employing
the same alkylation conditions outlined in Scheme 4, and all other alkylation techniques
outlined in the SI, failed to afford the desired alkylated material, but rather massive
decomposition and the recovery of 25. However, it was found by treating 25 to alkylation
conditions followed by immediate removal of the allyl group, with a short silica plug used
in between, gave access to the desired material in 39%. Removal of the MOM groups
was performed under standard conditions with methanolic HCl to access 26 in 66%
yield.1 Based upon these findings, we decided to explore if the triphenol analog of 26
could be accessed. The full MOM protection of 9 was accomplished under sodium

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hydride deprotonation followed by MOMCl addition to give access to 27 in 83% yield,
which was elaborated onto 28 in 94% yield. However, all attempts at alkylating this
material failed, including the sequential allyl deprotection. Curious as to whether the
presence of three MOM groups could possibly shut down the alkylation due to chelation
of the Lewis acid, 9 was transformed into its di-MOM protected 29 in 79% yield.
Methylation of the free phenol with dimethyl sulfate proceeded in an 91% yield that was
subsequently subjected to the aldol condensation to afford 30 in 80% yield, 73% yield
over two-steps. We were pleasantly surprised to observe the successful alkylation
under standard condition, with immediately allyl deprotection. Removal of the MOM
groups gave access to 2 in a 33% yield over two-steps, for an overall yield of 16.7%
over six-synthetic steps. Hydrogenation of 2 gave access to uvaretin in 90% yield, with
an overall yield of 15.1% over seven-synthetic steps. Subjecting 29 to aldol conditions
gave rise to chalcone 31. However, subjecting 31 to multiple alkylation conditions,
followed by the conditions used to access 2, failed to afford the desired material.

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Scheme 8 Elaboration of 22 onto the natural products uvaretin (1) and 2.
2.3 Biology
2.3.1 Cytotoxicity Evaluation of Uvaretin, 2, and compounds accessed
After accessing both natural products as well as a collection of small molecules based
upon the chalcone core, we pursued biological evaluation of this library set. Initially, the
collection was accessed in the cervical cancerous cell line HeLa to probe if the activity
warrants the expansion to screen other cells lines. Cellular viability was assessed via
Alamar Blue quantification,47-49 measure of alive cells as a function of electron transport
activity. Summarized in Table 1 are the IC50 values, concentration required to inhibit cell
proliferation by 50% of the control (Table S2 provides all structures and their
corresponding IC50 values). Several of the compounds screened showed promising
cytotoxicity, such as 10, 19, 26, and uvaretin. The low µM IC50’s observed with these
four compounds, in addition to the large number of high single and low double digits
values promoted us to expand our evaluation. The small library was then assessed in
five other cancerous cell lines: lymphoma (U937), lung (A549), pancreatic (MIA PaCa-
2), acute lymphocytic leukemia (Reh), and colon (HCT-116). A large percentage of
compounds were observed to have promising activity in the U937, A549, and MIA
PaCa-2 cell lines. However, there was limited activity within the Reh cell line ranging
from 9.2 to 19.4 M. The activity within HCT-116 was very limited, with only two
possessing activities below the 20 M threshold.
Table 1 Evaluation of natural products uvaretin (1) and 2, and the chalcone small library
set for cytotoxicity.

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Observed IC50 (µM)a
Cmpd
HeLa
>20
U937
>20
A549
> 20
MIA PaCa-2
>20
Reh
>20
HCT-116
>20
9
10
3.8 ±1.0
5.2 ±1.4
5.8 ±0.5
2.7 ±0.6
>20
7.2 ±0.9
6.7 ±0.8
7.5 ±1.1
4.2 ±1.4
>20
9.8 ±1.3
4.3 ±0.9
8.5 ±0.6
9.3 ±1.1
>20
14.3 ±1.0
>20
>20
>20
11
>20
>20
15
9.4 ±1.3
4.1 ±0.3
>20
12.6 ±2.3
>20
>20
19
18.6 ±2.5
>20
20
>20
21
>20
>20
19.7 ±2.2
>20
18.2 ±1.7
>20
>20
>20
22
18.7 ±3.1
14.0 ±1.0
4.8 ±0.6
3.1 ±0.5
>20
>20
>20
>20
24
13.3 ±2.1
2.5 ±0.5
6.8 ±1.7
11.7 ±1.3
7.4 ±0.8
8.1 ±2.0
5.9 ±1.1
>20
16.9 ±1.6
3.5 ±0.8
5.8 ±1.8
>20
>20
>20
>20
25
5.6 ±0.7
>20
19.4 ±3.2
9.7 ±2.6
>20
>20
26
>20
27
6.1 ±1.6
>20
>20
28
12.2 ±0.9
11.5 ±1.1
9.7 ±1.3
16.7 ±0.6
4.6 ±1.4
3.7 ±0.8
>20
>20
>20
29
8.4 ±1.3
4.2 ±1.9
>20
11.8 ±2.6
2.2 ±0.6
7.8 ±0.4
5.1 ±1.8
2.0 ±1.1
>20
>20
30
9.2 ±0.9
>20
>20
31
2
>20
2.3 ±1.0
3.6 ±1.1
4.3 ±2.1
2.2 ±1.0
>20
19.5 ±3.1
>20
Uvaretin (1)
11.3 ±1.5
a
Cytotoxicity was evaluated in 384-well plates over a 72 h treatment. Adherent cells were seeded at 1,500 cells/well, whereas
suspension cells at 2,200 cells/well. Cellular viability was evaluated via Alamar Blue. Doxorubicin was used as the positive cell
death control, and wells with only cells as the alive control.
2.3.2 Identification of Small Molecule Potentiators
There has been much effort placed in the discovery of small molecules that act as
positive potentiators; a compound that increases the efficacy of a drug without
increasing the dosage of the drug. The discovery of such potentiators, when used in
parallel with known therapeutics, allow for lower dosages to be administered while

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retaining the same therapeutic profile. The benefit of this strategy is that the toxicities of
the drug are decreased as the drug dosage is lowered. The discovery of positive
potentiators is an arduous task. Most commonly, this is done through screening
campaigns of newly accessed small molecules with therapeutic agents. Investigations
are currently underway with the small molecules accessed in this work as potentiators
against known therapeutic agents. One agent, 6-thiopurine (6TP), a currently a
prescribed drug in the treatment of acute lymphocyte leukemia, acts as a nucleotide
mimic which upon DNA incorporation causes apoptosis via base pair mis-matching.
Chalcones 28, 30, and 31 were shown to have IC50 values of 11.8, 2.2, and 7.8 M,
respectively, in MIA PaCa-2. There are no reported therapeutic properties of 6TP within
this pancreatic cell line. Investigations into the possible potentiating properties of these
three chalcones with 6TP in MIA PaCa-2 were conducted to probe the possible
usefulness in the small molecule chalcone collection assembled.
Assessing the synergist properties of 28, 30, and 31 with 6TP was performed in a
matrix format, consisting of a 3x5 matrix. In this, two concentrations of the chalcone
were employed that would induce 10 to 20% cell death within a 72-hour period. Four
concentrations of 6TP were chosen so that 50% cell death would be observed within the
same time period. The combinational effects on cell death is shown in Figure 3 (within
the red tables). There was no significant change in cell death at various concentrations
of 28 and 6TP, with percentages remaining between 14-21%. While an overall increase
in cell death was observed with chalcone 31, the overall change in cell death did not
exceed the cellular death observed by 6TP alone. There was a noted increased in
cellular death in the combination of 30 and 6TP, resulting in a 100% increase in death

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as compared to 6TP alone. The effects of these potentiating studies were assessed by
determination of their combination index (CI), a value determined through employing the
Chou-Talalay protocol.50 CI values closer to 0 represented strong synergism, 1 an
additive effect, and values greater than 1 denote antagonism in this method. CI values
for 28 and 31 show mild synergism to antagonism and strong antagonism, respectively.
However, 30 was shown to possess a CI value of 0.19, at the higher concentrations of
both compounds, corresponding to strong synergism. 6TP is not prescribed to treat
pancreatic cancer, as such, the synergism observed between 30 and 6TP within Mia
PaCa-2 effectively illustrates the importance in full biological evaluation of all small
molecules accessed within total synthesis routes. To our surprise, similar strong
synergism between 30 and 6TP was not observed within the acute lymphocytic
leukemia cancerous cell line Reh, in which 6TP is prescribed for. This illustrates the
difficulty in discovering positive potentiating agents for specific drugs in varying cell
lines.
MIA PaCa-2
Reh


[Cmpd 30] ( M)

[Cmpd 30] ( M)
[Cmpd 9] (


M)
[Cmpd 10] ( M)

[Cmpd 8] (


M)
[Cmpd 10] ( M)
[Cmpd 28] ( M)
[Cmpd 30] ( M)
0
2.5
5
0
2.5
5
0
0.0
2.5
6.1
7.0
7.2
5
0
0.0
2.5
8.1
5
9.0
0%
0
0.0 21.1 20.0
0
0.0 10.2 16.2
0
7.2
8.1
8.2
0
10 6.9 14.2 18.4
25 6.4 15.0 17.3
50 13.8 16.9 17.0
10 6.9 16.5 25.4
25 6.4 18.6 30.0
50 13.8 25.1 40.8
10 6.9
25 6.4
50 13.8 9.7 13.0
10 10.8 11.1 12.7
25 12.2 13.5 19.1
50 21.9 22.1 26.1
100 49.5 51.0 51.0
100 30.7 17.6 19.3 100 30.7 49.1 61.2 100 30.7 15.2 19.9
100%
2
1
0
--
2.5
--
5
--
0
--
2.5
--
5
--
0
--
2.5
--
1.21 1.13
2.04 1.87
2.18 1.42
2.16 1.43
5
--
0
--
2.5
--
0.81 0.67
1.36 0.84
1.36 1.06
0.63 0.64
5
--
additive
effect
0
0
0
0
25 --
50 --
100 --
200 --
0.24 0.47
0.56 0.57
0.96 1.01 100 --
1.79 2.09 200 --
25 --
50 --
0.67 0.55
0.79 0.51
0.72 0.36 100 --
0.31 0.19 200 --
25 --
50 --
25 --
50 --
100 --
200 --
mild
synergism
strong
synergism
0
Figure 3 Evaluation of chalcones 28, 30, and 31 potentiation properties with 6-
thiopurine in the cancerous cells line Mia PaCa-2 (pancreatic) and Reh (acute
lymphocytic leukemia). Potentiation performed in a 3x5 matrix, and synergy assessed.
(n = biological replicates).

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With the discovery of 30 possessing strong synergy with 6TP in a cell line that it is
not currently prescribed in, we decided to expand our small molecule potentiation
screens. Noting that these investigations are both time and financially intensive, we
limited further studies to the two natural products (1 and 2) accessed in this work and
their trimethoxy (B-ring) analogs 20 and 19, respectively. Employing the same
procedures previously described, 6TP potentiation studies outlined in Figure 2, these
four compounds were evaluated within the same cell lines used in our general IC50
screens (shown in Table 1) towards doxorubicin, etoposide, paclitaxel, and 6TP. Figure
4 illustrates the median CI index value obtained from each potentiating screen for each
of the four compounds with the four cytotoxic agents in five cell lines.
Figure 4 Median CI values for each chalcone/chemotherapeutic combination for each
cell line. CI values < 1 are synergistic, lower values representative of higher levels of
synergy. CI values of 1 denote additive effects of the two compounds, and values > 1
antagonistic effects (n = three biological replicates).

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Uvaretin (1), possessing the most potent cytotoxicity as a sole agent, showed mild
synergist to additive effects in HeLa, U937, A549, and Reh. Within HCT-116, uvaretin
was shown to possess antagonism properties with doxorubicin, 6-thiopurine, and
etoposide (greater to lower values). A similar pattern of potentiation was observed with
2, thus showing that these two natural products fail to give significant synergistic
properties. Interestingly, it was found that 20, the trimethoxy analog of uvaretin, while
possessing no IC50 values below 20 M possesses greater synergism with all four
drugs. Most notably, 20 was found to have a CI value of 0.11 with doxorubicin in HeLa,
and 0.22 with 6-thiopurine in U937. In contrast, uvaretin possesses a low single M IC50
sole agent, and mild synergy to additive effects. It was also shown that low synergism
was observed with 20 in combination with doxorubicin, paclitaxel, and 6-thiopurine. A
property not observed with either natural product. Evaluation of 19, the trimethoxy
analog of 2, also showed an increase in overall combinational (additive) and synergistic
properties, with a median CI value of 0.12 between 19 and doxorubicin within HeLa.
Low synergistic effects were observed in HCT-116 between 19 and etoposide,
paclitaxel and 6-thiopurine.
3. Conclusion
In summary, the total syntheses of the natural products uvaretin (1) and its
unsaturuated enone analog (2) has been accomplished in 15.1% over seven steps and
16.7% over six steps, respectively. While the route delineated gains access to both
natural products, in this body of work, the yields are 3-5.5 folds greater than the route
developed by Malterud. However, the previous route does gain access to 1 and 2 in 1-2

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shorter synthetic steps, but, reported starting materials were pre-synthesized and not
disclosed in the original manuscript. The route developed, highlighting an early stage
chalcone core installation, allowed for the construction of a small chalcone library that
was evaluated for sole agent cytotoxicity and select members further investigated for
potentiating properties with known chemotherapeutics. Natural products 1 and 2 were
found to have low single M IC50 values in HeLa, U937, A549 and MIA PaCa-2
cancerous cell lines and moderate double digit M in Reh and HCT-116. Also, 31 other
compounds from this library were found to possess single digit M IC50 activity as sole
agents. Chalcone 30 was shown to possess moderate synergy with 6TP in the
pancreatic cancer cell line MIA PaCa-2. Compound 19 and 20, analogs of 2 and 1,
respectively, were observed to have promising potentiating properties with doxorubicin,
etoposide, pacilitaxel, and 6TP. Further investigations are needed to explore the mode
of action for this potentiation, as well as the evaluation of the other library members.
4. Experimental Section
4.1 Chemistry
All reagents were commercially available and used without purification unless
otherwise stated. NMR spectra were recorded with a Varian 400 MHz instrument. The
chemical shifts are given in parts per million (ppm) relative to residual CHCl3 at  7.26
ppm or DMSO at  2.50 ppm for proton spectra and relative to CDCl3 at  77.23 ppm or
DMSO at  39.52 ppm for carbon spectra, unless otherwise noted. Low-resolution mass
spectra were obtained using a Waters Xevo-TQD via direct injection; samples were
dissolved in methanol, filtered, and the supernatant injected. Flash column

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chromatography was performed with silica gel grade 60 (230-400 mesh).
Dichloromethane (CH2Cl2), methanol (CH3OH), and N,N-dimethylformamide (DMF)
were all degassed with argon and passed through a solvent purification system
containing alumina or molecular sieves. All commercially available reagents were used
as received. All procedures including anhydrous solvents were performed with
rigorously dried glassware under inert atmosphere.
4.1.1 Aldol Condensation General Procedure. To a round bottom flask (RBF) was
added the acetophenone species (1.0 eq.), benzaldehyde (1.0 eq.), and EtOH (20 mL)
and brought to 0 C. Once at temperature, a solution of KOH (17 eq) in water (25 mM
final concentration) was added dropwise, after which the mixture was brought to 25 C
and left to stir for 14 h. The reaction was diluted with EtOAc, washed with water,
acidified with 1 M HCl, and extracted with EtOAc (x2). The organic layers were
combined, washed with brine, dried over sodium sulfate and concentrated to afford the
crude material. Specific purification protocols are given with each specific reaction.
4.1.2 General Alkylation Procedure. To a flamed dried RBF under an argon
atmosphere was added chalcone (1.0 eq.) and dry dioxane (final concentration of 46
mM) and stirred at RT. In a separate flamed dried RBF under an argon atmosphere was
added BF3•Et2O (3.05 eq.) and dioxane (final concentration of 0.56 M), this solution was
added to the previously prepared RBF in four portions 10 min apart. The reaction was
then brought to 60 C and stirred for 3 h. The reaction was cooled, diluted with EtOAc,
washed with water (x2), and extracted with EtOAc (x2). The combined organic layers
were combined, washed with brine, dried over sodium sulfate, and concentrated under
reduced pressure. Specific purification protocols are given with each specific reaction.

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4.1.3 General Allyl Deprotection Conditions. To a flamed dried RBF under an argon
atmosphere was added chalcone species (1.0 eq.), K2CO3 (6 eq.), and Pd(PPh3)4 (0.02
eq.) in MeOH (final concentration relative to chalcone 16 mM) and allowed to stir at
reflux for 2 h. The reaction mixture was filtered through a short silica plug, rinsed with
MeOH (1 vol. eq. to initial MeOH), and concentrated to afford the desired product.
4.1.4 General Enone Reduction Procedure. To a flamed dried RBF under an argon
atmosphere was added the enone material (1.0 eq.) and 10% palladium over carbon in
MeOH (2.3 M final concentration relative to the enone). A hydrogen balloon was
introduced and the mixture was left to stir for 25 C for 2 h, filtered through Celite, and
rinsed with MeOH or CHCl3. The filtrate was concentration to afford the ketone species.
4.1.5 2,4,6-Trihydroxyacetophenone (9):51 To a RBF under an argon atmosphere
was added BF3·OEt2 (7.5 mL, 59.4 mmol) and acetic anhydride (1.9 mL, 19.8 mmol)
followed by phloroglucinol (2.5 g, 19.8 mmol) and allowed stirred at room temperature
(RT). After 15 h, the reaction mixture was poured onto a 10% NaOAc solution (70 mL)
and left to stir overnight (O/N) under ambient atmosphere. The precipitate was filtered
1
off and washed with water to obtain 9 (2.9 g) in 88% yield. H NMR (400 MHz,
13
Methanol-d4) δ 5.79 (s, 2H), 2.59 (m, 3H). C NMR (101 MHz, Methanol-d4) δ 204.56,
166.32, 165.90, 105.60, 95.59, 32.71.
4.1.6 2,4,6-Trimethyoxyacetophenone (10):52, 53 To a flamed RBF under an argon
atmosphere was added 9 (0.5 g, 2.98 mmol), K2CO3 (2.0 g, 14.9 mmol), and anhydrous
acetone (10 mL). The reaction was allowed to stir at 25 C for 15 h, and then brought to
reflux for an additional 4 h. The reaction was quenched by the addition of saturated
ammonium chloride and extracted with EtOAc (x3). The organic layers were combined,

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washed with brine, dried over sodium sulfate and concentrated under reduced pressure.
The crude material was purified via flash silica gel chromatograph (1:1, Hex:EtOAc) to
1
afford the 10 (556 mg) in 89% yield. H NMR (CDCl3, 400 MHz)  (ppm): 6.10 (s, 2H),
13
3.82 (s, 3H), 3.79 (s, 6H), 2.46 (s, 3H). C NMR (CDCl3, 101 MHz)  (ppm): 202.14,
162.54, 158.57, 113.78, 90.67, 56.04, 55.66, 32.81.
4.1.7 (E)-3-phenyl-1-(2,4,6-trimethoxyphenyl)prop-2-en-1-one (11):25 The aldol
condensation general procedure was followed using 10 (0.62 g, 2.95 mmol) and 0.31
mL of benzaldehyde. The crude material was purified by flash silica gel chromatography
1
(2:1, Hex:EtOAc) to give 11 (0.7 g, yellow crystals) in 80% yield. H NMR (CDCl3, 400
MHz)  (ppm): 7.54-7.52 (m, 2H), 7.39-7.35 (m, 5H), 6.97 (d, 1H, J = 12Hz), 3.87 (s,
3H), 3.78 (s, 6H). 13C NMR (DMSO, 101 MHz)  (ppm): 193.23, 161.94, 158.06, 143.50,
134.34, 130.44, 128.99, 128.94, 128.45, 110.98, 91.07, 55.80, 55.45. LRMS (ESI): m/z
+
calcd for C18H19O4 : [M+ H]+ 299.12, found 299.12.
4.1.8 2-(Allyloxy)benzaldehyde (13): To a flamed dried RBF under an argon
atmosphere was added salicyaldehyde (12, 10 g, 82.0 mmol), K2CO3 (17 g, 123.0
mmol) and DMF (30 mL) and left to stir. Once homogenous allyl bromide (10 mL, 123.0
mmol) was added and the reaction was left to stir at 25 C for 2 h. The reaction mixture
was diluted with EtOAc, washed with saturated ammonium chloride, water (x4), and
brine. The organic layers were dried over sodium sulfate and concentrated under
1
reduced pressure to furnish 13 (12 g, colorless oil) in 90% yield. H NMR (CDCl3, 400
MHz)  (ppm): 10.54 (s, 1H), 7.84 (dd, J = 7.7, 1.8 Hz, 1H), 7.53 (ddd, J = 8.9, 7.4, 1.9
Hz, 1H), 7.06 – 6.95 (m, 2H), 6.08 (ddt, J = 17.1, 10.4, 5.1 Hz, 1H), 5.45 (dd, J = 17.3,
13
1.6 Hz, 1H), 5.34 (dd, J = 10.6, 1.4 Hz, 1H), 4.66 (dt, J = 5.2, 1.6 Hz, 2H). C NMR

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(CDCl3, 101 MHz)  (ppm): 189.96, 161.15, 136.04, 132.60, 128.66, 125.33, 121.08,
118.29, 113.07, 69.40. LRMS (ESI): m/z calcd for C10H10O2Na+: [M+ Na]+ 185.06,
found 185.06.
4.1.9 2-(Allyloxy)benzylalcohol (14): To a flamed dried RBF under an argon
atmosphere was added 13 (12 g, 73.8 mmol) and methanol (100 mL), which was stirred
and cooled to 0 C. Once at temperature sodium borohydride (5.6 g, 147.6 mmol) was
added in three equal portions over 10 min, then left to stir at 0 C for 1 h. The reaction
mixture was diluted with EtOAc, quenched with the addition of 1 M HCl, stirred for 2 h,
and extracted with EtOAc (x2). The organic layers were combined, washed with brine,
dried over sodium sulfate and concentrated under reduced pressure. The crude material
was purified via flash silica gel chromatography to afford 14 (10 g, colorless oil) in 83%
yield. 1H NMR (CDCl3, 400 MHz)  (ppm): 7.32 (dd, J = 7.4, 1.6 Hz, 1H), 7.29 – 7.22 (m,
1H), 6.96 (dd, J = 8.1, 6.8 Hz, 1H), 6.87 (d, J = 8.2 Hz, 1H), 6.13 – 6.01 (m, 1H), 5.43
(dd, J = 17.3, 1.6 Hz, 1H), 5.30 (dd, J = 10.5, 1.5 Hz, 1H), 4.72 (s, 2H), 4.59 – 4.51 (m,
2H), 2.84 (bs, 1H). 13C NMR (CDCl3, 101 MHz)  (ppm): 156.48, 133.38, 129.78,
128.90, 128.81, 121.08, 117.73, 111.68, 68.94, 61.83. LRMS (ESI): m/z calcd for
+
C10H13O2 : [M+ H]+ 165.09, found 165.09.
4.1.10 (E)-1-(3-(2-(allyloxy)benzyl)-2,4,6-trimethoxyphenyl)-3-phenylprop-2-en-1-one
(15): The general alkylation procedure was followed using 11 (0.11 g, 0.37 mmol) and
14 (72 mg, 0.44 mmol). The crude material was purified by flash silica gel
chromatography (2:1, Hex:EtOAc) to give 15 (52 mg, light yellow solid) in 58% yield. 1H
NMR (CDCl3, 400 MHz)  (ppm): 7.55 – 7.50 (m, 2H), 7.43 – 7.39 (m, 1H), 7.38 – 7.35
(m, 2H), 7.12 (ddd, J = 8.8, 6.9, 2.2 Hz, 1H), 7.03 (d, J = 16.0 Hz, 1H), 6.86 – 6.77 (m,

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3H), 6.38 (s, 1H), 6.12 (ddt, J = 17.3, 10.2, 5.0 Hz, 2H), 5.48 (dq, J = 17.3, 1.8 Hz, 1H),
5.28 (dq, J = 10.6, 1.6 Hz, 1H), 4.61 (dq, J = 5.3, 1.8 Hz, 2H), 4.01 (s, 2H), 3.84 (s, 3H),
3.81 (s, 3H), 3.52 (s, 3H). 13C NMR (CDCl3, 101 MHz)  (ppm): 194.78, 160.84, 158.24,
157.28, 156.46, 144.83, 135.11, 133.95, 130.51, 130.08, 129.02, 128.97, 128.70,
128.29, 126.67, 120.62, 117.03, 116.70, 114.48, 111.42, 91.72, 69.00, 63.07, 56.26,
+
56.04, 22.98. LRMS (ESI): m/z calcd for C28H29O5 : [M+ H]+ 445.20, found 445.20.
4.1.11 (E)-1-(3-(2-hydroxybenzyl)-2,4,6-trimethoxyphenyl)-3-phenylprop-2-en-1-one
(19): The allyl deprotection procedure was followed using 15 (29 mg, 0.065 mmol). The
product 19 (20 mg, white solid) was obtained in 76% yield. 1H NMR (CDCl3, 400 MHz) 
(ppm): 7.52 (dd, J = 6.7, 3.0 Hz, 2H), 7.41 – 7.33 (m, 6H), 7.11 (td, J = 8.4, 7.9, 1.7 Hz,
1H), 6.98 (d, J = 16.1 Hz, 1H), 6.87 – 6.80 (m, 2H), 6.33 (s, 1H), 3.95 (s, 3H), 3.86 (s,
13
2H), 3.84 (s, 3H), 3.78 (s, 3H). C NMR (CDCl3, 101 MHz)  (ppm): 194.24, 159.71,
157.47, 155.92, 155.01, 145.76, 134.91, 131.87, 130.71, 129.07, 128.79, 128.50,
128.10, 125.90, 120.06, 116.52, 116.36, 114.16, 92.38, 63.86, 56.33, 56.15, 24.58
+
LRMS (ESI): m/z calcd for C25H25O5 : [M+ H]+ 405.17, found 405.17.
4.1.12 1-(3-(2-hydroxybenzyl)-2,4,6-trimethoxyphenyl)-3-phenylpropan-1-one (20):
The enone reduction procedure was followed using 19 (3 mg, 0.007 mmol) and 10%
1
Pd/C (1 mg) to afford 20 (3 mg) in quantitative yields. H NMR (CDCl3, 400 MHz) 
(ppm): 7.34 (dd, J = 7.5, 1.7 Hz, 1H), 7.28 – 7.15 (m, 6H), 7.11 – 7.07 (m, 1H), 6.85 –
6.78 (m, 2H), 6.25 (s, 1H), 3.90 (s, 3H), 3.80 (s, 2H), 3.76 (s, 3H), 3.74 (s, 3H), 3.09 (t, J
13
= 7.5 Hz, 2H), 3.00 (t, J = 7.0 Hz, 2H). C NMR (CDCl3, 101 MHz)  (ppm): 203.58,
159.61, 156.73, 155.19, 154.90, 141.38, 131.77, 128.74, 128.53, 128.12, 126.11,

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125.81, 120.08, 118.42, 116.53, 114.35, 92.31, 64.38, 56.12, 46.51, 30.04, 24.45.
+
LRMS (ESI): m/z calcd for C25H27O5 : [M+ H]+ 407.18, found 407.18.
4.1.13 (E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-phenylprop-2-en-1-one (21): De-
methylation Approach. To a flamed dried RBF was added 11 (0.129 mg, 0.40 mmol)
and PhCl (4 mL) followed by AlCl3 (0.11 g, 0.8 mmol) and left to stir O/N at RT. The
reaction was then brought to 70 C and allowed to stir for an additional 24 h. The
reaction was quenched with saturated Rochelle Salt and stirred for 30 min, and then
extracted with EtOAc (x3). The organic layers were combined, dried over sodium
sulfate, and concentrated under reduce pressure. The crude material was purified via
flash silica gel chromatography (7:3, Hex:EtOAc) to afford 21 (77 mg) with inconsistent
yields. Aldol Approach. The aldol condensation general procedure was followed using
22 (0.4 g, 2.0 mmol) and 0.24 mL of benzaldehyde. The crude material was purified by
flash silica gel chromatography (7:3, Hex:EtOAc) to give 21 (0.7 g, yellow crystals) in
1
99% yield. H NMR (CDCl3, 400 MHz)  (ppm): 7.88 (d, J = 15.6 Hz, 1H), 7.76 (d, J =
15.5 Hz, 1H), 7.62 – 7.60 (m, 2H), 7.42 – 7.38 (m, 3H), 6.11 (d, J = 2.4 Hz, 1H), 5.97 (d,
J = 2.4 Hz, 1H), 3.92 (s, 3H), 3.84 (s, 3H). 13C NMR (CDCl3, 101 MHz)  (ppm): 192.83,
168.64, 166.48, 162.74, 142.50, 135.79, 130.28, 129.10, 128.57, 127.76, 106.54, 94.05,
+
91.47, 56.06, 55.79. LRMS (ESI): m/z calcd for C17H17O4 : [M+ H]+ 285.11, found
285.11.
4.1.14 1-(2-hydroxy-4,6-dimethoxyphenyl)ethan-1-one (22): To a flamed dried RBF
under an argon atmosphere was added 9 (0.5 g, 2.98 mmol), K2CO3 (2 g, 14.9 mmol),
Me2SO4 (0.85 mL, 8.94 mmol) in anhydrous acetone (10 mL) and stirred at 25 C for 15
h. The reaction was quenched with the addition of saturated ammonium chloride and

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extracted with EtOAc (x3). The organic layers were combined, washed with brine, dried
over sodium sulfate, and concentrated under reduce pressure. The crude material was
purified via flash silica gel chromatography (2:1, Hex:EtOAc) to afford 22 (501 mg) in
86% yield. 1H NMR (CDCl3, 400 MHz)  (ppm): 6.05 (d, J = 1.6 Hz, 1H), 5.91 (d, J = 2.4
Hz, 1H), 3.85 (d, J = 0.7 Hz, 3H), 3.81 (d, J = 0.7 Hz, 3H), 2.60 (s, 3H). 13C NMR
(CDCl3, 101 MHz)  (ppm): 203.34, 167.80, 166.29, 163.12, 104.99, 93.70, 90.94,
+
55.75, 33.13. LRMS (ESI): m/z calcd for C10H13O4 : [M+ H]+ 197.08, found 197.08.
4.1.15 1-(2,4-dimethoxy-6-(methoxymethoxy)phenyl)ethan-1-one (24): To a RBF
was added 22 (0.58 g, 2.95 mmol) to acetone (10 mL) followed by MOMCl (0.68 mL,
8.84 mmol) and K2CO3 (2.0 g, 14.8 mmol). The reaction was brought to reflux for 4 h,
quenched with saturated ammonium chloride, and extracted with EtOAc (x2). The organic
layers were combined, washed with brine, dried over sodium sulfate, and concentrated
under reduced pressure. The crude material was purified via flash silica gel
1
chromatography (7:3, Hex:EtOAc) to afford 24 (0.6 g, pale-yellow oil) in 58% yield. H
NMR (CDCl3, 400 MHz)  (ppm): 6.32 (s, 1H), 6.14 (s, 1H), 5.14 (s, 2H), 3.79 (s, 3H),
13
3.78 (s, 3H), 3.46 (s, 3H), 2.46 (s, 3H). C NMR (CDCl3, 101 MHz)  (ppm): 201.79,
162.34, 158.28, 155.95, 115.10, 95.06, 93.57, 92.47, 56.50, 56.01, 55.68, 32.77. LRMS
+
(ESI): m/z calcd for C12H17O5 : [M+ H]+ 241.10, found 241.10.
4.1.16 (E)-1-(2,4-dimethoxy-6-(methoxymethoxy)phenyl)-3-phenylprop-2-en-1-one
(25): The aldol condensation general procedure was followed using 24 (0.4 g, 1.66
mmol) and 0.19 mL of benzaldehyde. The crude material was purified by flash silica gel
chromatography (7:3, Hex:EtOAc) to give 25 (372 mg, pale-yellow solid) in 68% yield.
1H NMR (CDCl3, 400 MHz)  (ppm): 7.53-7.50 (m, 2H), 7.36-7.34 (m, 4H), 6.97 (d, 1H, J

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= 12 Hz), 6.39 (s, 1H), 6.22 (s, 1H), 5.12 (s, 2H), 3.83 (s, 3H), 3.76 (s, 3H), 3.39 (s, 3H).
13C NMR (CDCl3, 101 MHz)  (ppm): 194.52, 162.48, 158.40, 156.45, 144.71, 135.15,
130.49, 129.29, 129.08, 128.56, 113.00, 94.87, 93.59, 92.58, 56.47, 56.11, 55.73.
+
LRMS (ESI): m/z calcd for C19H21O5 : [M+ H]+ 329.13, found 329.13.
4.1.17 (E)-1-(6-hydroxy-3-(2-hydroxybenzyl)-2,4-dimethoxyphenyl)-3-phenylprop-2-
en-1-one (26): The general acylation procedure was followed using 25 (310 mg, 1.09
mmol) and 14 (215 mg, 1.31 mmol). The crude material was not columned, but rather
subjected to the allyl deprotection procedure to afford the carbon core of the uvaretin
family (25b, 183 mg) in 39% yield. The material was dissolved into MeOH (final
concentration 0.05 M) and a 10% HCl solution (1/2 vol. eq. of the MeOH) was added.1
The solution was refluxed for 30 min, the mixture poured onto cold water (2 vol. eq. to
MeOH) and extracted with EtOAc. The organic layers were combined, dried over
sodium sulfate, and concentrated under reduce pressure. The crude material was
purified via flash silica gel chromatography (1:1, Hex:EtOAc) to afford 26 in 66% yield.
1H NMR (CDCl3, 400 MHz)  (ppm): 7.92 – 7.79 (m, 4H), 7.66 – 7.58 (m, 3H), 7.42 (dt, J
= 5.2, 2.9 Hz, 4H), 6.87 (dd, J = 8.1, 1.3 Hz, 1H), 6.81 (td, J = 7.4, 1.3 Hz, 1H), 6.04 (s,
1H), 3.99 (s, 3H), 3.96 (s, 3H), 3.89 (s, 2H). 13C NMR (CDCl3, 101 MHz)  (ppm):
193.38, 163.90, 163.02, 162.14, 155.07, 143.38, 135.62, 131.91, 130.48, 129.12,
128.67, 127.93, 127.37, 126.47, 119.96, 116.71, 109.29, 106.39, 87.43, 56.18, 55.96,
+
23.35. LRMS (ESI): m/z calcd for C24H23O5 : [M+ H]+ 391.15, found 391.15.
4.1.18 1-(2,4,6-tris(methoxymethoxy)phenyl)ethan-1-one (27): To a flamed dried
RBF under an argon atmosphere was added 9 (0.5 g, 2.97 mmol) in DMF (15 mL) and
cooled to 0 C. NaH (60% dispersion, 0.53 g, 13.3 mmol) was then added slowly and

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allowed to stir for 5 min. MOMCl (1.01 mL, 13.3 mmol) was added dropwise over 15
min. The reaction was stirred, while being warmed to RT, for 30 min, quenched with
water, and then extracted with EtOAc (x2). The organic layers were combined, washed
with water and brine, dried over sodium sulfate, and concentrated under reduced
pressure. The crude material was purified by flash silica gel chromatography (7:3,
1
Hex:EtOAc) to give 27 (0.7 g) in 83% yield. H NMR (CDCl3, 400 MHz) δ 6.50 (s, 2H),
5.13 (s, 2H), 5.13 (s, 4H), 3.46 (s, 3H), 3.45 (s, 6H), 2.48 (s, 3H). 13C NMR (CDCl3, 101
MHz) δ 201.65, 159.68, 155.41, 117.16, 97.34, 94.99, 94.69, 56.55, 56.44, 56.34,
32.76. LRMS (ESI): m/z for C14H20O7Na+: [M+Na]+ 323.11; found 323.11.
4.1.19 (E)-3-phenyl-1-(2,4,6-tris(methoxymethoxy)phenyl)prop-2-en-1-one (28): The
aldol condensation general procedure was followed using 27 (170 mg, 0.5 mmol) and
0.05 mL of benzaldehyde. The crude material was purified by flash silica gel
1
chromatography (4:1, Hex:EtOAc) to give 28 (195 mg) in a quantitative yield. H NMR
(CDCl3, 400 MHz) δ 7.54 – 7.49 (m, 2H), 7.39 – 7.33 (m, 4H), 6.97 (d, J = 16.2 Hz, 1H),
6.57 (s, 2H), 5.18 (s, 3H), 5.11 (s, 4H), 3.50 (s, 3H), 3.38 (s, 6H). 13C NMR (CDCl3, 101
MHz) δ 194.50, 159.88, 156.06, 145.22, 135.02, 130.61, 129.22, 129.12, 128.55,
114.99, 97.36, 94.99, 94.81, 94.79, 56.51. LRMS (ESI): m/z calcd. for C21H24O7Na+:
[M+Na]+ 411.14; found 411.14.
4.1.20 1-(2-hydroxy-4,6-bis(methoxymethoxy)phenyl)ethan-1-one (29): To a RBF
under an argon atmosphere was added 9 (500 mg, 2.97 mmol) and CH2Cl2 (15 mL),
which was then cooled to 0 °C and then diisopropylethylamine (1.6 mL, 8.91 mmol) and
MOMCl (0.5 mL, 6.5 mmol) was added. The solution was then stirred O/N, allowed to
warm to RT, and then quenched with methanol and washed with brine (x2). The

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DOI: 10.1039/C9MD00052F
combined organic layers were dried over anhydrous sodium sulfate, concentrated, and
purified via flash silica gel chromatography (4:1, Hex:EtOAc) to afford 29 in 79% yield
1
(601 mg). H NMR (CDCl3, 400 MHz) δ 13.70 (s, 1H), 6.24 (1H), 6.22 (s, 1H), 5.24 (s,
2H), 5.15 (s, 2H), 3.50 (s, 3H), 3.45 (s, 3H), 2.63 (s, 3H). 13C NMR (CDCl3, 101 MHz) δ
203.40, 167.02, 163.66, 160.57, 107.12, 97.32, 94.69, 94.21, 56.91, 56.64, 33.21.
LRMS (ESI): m/z calcd. for C12H16ONa+: [M+Na]+ 279.08; found 279.08.
4.1.21
(E)-1-(2-methoxy-4,6-bis(methoxymethoxy)phenyl)-3-phenylprop-2-en-1-one
(30): To a flame dried RBF under an argon atmosphere was added dry acetone (15 mL)
to which was added 29 (400 mg, 1.56 mmol) under vigorous stirring. Once a
homogenous solution was obtained, K2CO3 (1.07 g, 7.8 mmol) and Me2SO4 (.74 mL, 7.8
mmol, 5 eq.) were added. The reaction mixture was refluxed for 4 h, quenched with
saturated ammonium chloride, and extracted with EtOAc (x2). The organic layers were
combined, dried over sodium sulfate, concentrated, and purified via flash silica gel
chromatography (7:3 Hex:EtOAc) to obtain the desired methylated acetophenone
material (29b). The aldol condensation general procedure was followed using 29b (350
mg, 1.29 mmol) and 0.16 mL of benzaldehyde. The crude material was purified by flash
silica gel chromatography (7:3, Hex:EtOAc) to afford 30 (408 mg) in a 73% overall yield.
1H NMR (CDCl3, 400 MHz) δ 7.52 (dq, J = 6.5, 4.0, 3.0 Hz, 2H), 7.38 – 7.34 (m, 4H),
6.96 (d, J = 16.1 Hz, 1H), 6.50 (dd, J = 6.2, 2.0 Hz, 1H), 6.37 (d, J = 2.0 Hz, 1H), 5.20
(s, 1H), 5.11 (s, 1H), 3.76 (s, 3H), 3.51 (s, 3H), 3.39 (s, 3H). 13C NMR (CDCl3, 101
MHzd) δ 194.56, 160.10, 158.77, 156.16, 144.91, 135.13, 130.52, 129.19, 129.07,
128.58, 96.15, 94.84, 94.80, 94.21, 56.53, 56.48, 56.16. LRMS (ESI) m/z calcd. for
+
C20H23O6 : [M+H]+ 359.15; found 359.15.

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DOI: 10.1039/C9MD00052F
4.1.22 2’, 4’-Dihydroxy-3’-(2-hydroxybenzyl)-6’-methoxychalcone (2, c-benzylated
chalcone): The general alkylation procedure was followed using 30 (247 mg, 0.69
mmol) and 14 (215 mg, 0.83 mmol). The crude material was not purified by column
chromatography, but rather subjected to the allyl deprotection procedure to afford the
carbon core of the uvaretin family (30b) in 51% yield. The material was dissolved into
MeOH (final concentration 0.05 M) and a 10% HCl solution (1/2 vol. eq. of the MeOH)
was added.1 The solution was refluxed for 30 min, the mixture poured onto cold water (2
vol. eq. to MeOH) and extracted with EtOAc. The organic layers were combined, dried
over sodium sulfate, and concentrated under reduce pressure. The crude material was
purified via flash silica gel chromatography (1:1, Hex:EtOAc) to afford 2 (86 mg) in 65%
1
yield, with an overall yield of 33% over two-steps. H NMR (CDCl3, 400 MHz)  (ppm):
15.06 (s, 1H), 7.87 (d, J = 15.6 Hz, 1H), 7.76 (d, J = 15.6 Hz, 1H), 7.62 – 7.54 (m, 3H),
7.39 (d, J = 6.0 Hz, 3H), 7.07 (t, J = 7.7 Hz, 1H), 6.85 (t, J = 7.9 Hz, 2H), 5.96 (s, 1H),
13
3.91 (s, 2H), 3.87 (s, 1H), 3.82 (s, 3H). C NMR (CDCl3, 101 MHz)  (ppm): 192.89,
165.40, 161.97, 161.52, 153.52, 142.37, 135.79, 132.15, 130.17, 129.02, 128.53,
127.83, 127.74, 127.15, 120.85, 115.86, 108.05, 106.12, 91.80, 55.91, 22.81. LRMS
+
(ESI): m/z calcd for C23H21O5 : [M+ H]+ 377.13, found 377.13.
4.1.23 Uravetin (1): The enone reduction procedure was followed using 2 (5 mg,
1
0.13 mmol) and 10% Pd/C (3 mg) to afford 1 (4.5 mg) in 90% yield. H NMR (CDCl3,
400 MHz)  (ppm): 7.54 (d, J = 7.6 Hz, 1H), 7.33 – 7.28 (m, 3H), 7.23 (d, J = 8.2 Hz,
2H), 7.08 (t, J = 7.8 Hz, 1H), 6.84 (dd, J = 13.2, 7.6 Hz, 2H), 5.91 (s, 1H), 3.90 (s, 2H),
13
3.77 (s, 3H), 3.30 (t, J = 7.8 Hz, 2H), 2.98 (t, J = 7.8 Hz, 2H). C NMR (CDCl3, 101
MHz)  (ppm): 205.41, 163.63,162.31, 155.02, 141.73, 131.91, 128.67, 128.65, 127.92,