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the presence of triethylamine (TEA) and a catalytic amount of
piperidine in toluene at reux to furnish the acid building block
3 (80%).
Notes and references
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Scheme 2 depicts the synthesis of the amide building block 4
in four steps starting from tyramine 6 in an approach similar to
the literature precedent.19,20 Reductive methylation of tyramine
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amine 10 in 98% yield. Bromination of 10 with Br2 in the
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quent O-alkylation of 11 with Boc-protected 3-bromopropyl-
amine gave 12 (93%), which was converted into the
dihydrochloride salt of amine 4 upon treatment with 4 M HCl in
methanol.
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Finally, the amidation between 3 and 4 were performed by
using DIC with a catalytic amount of DMAP in the presence of
TEA in DCM, leading to the formation of psammaplysene A
(Scheme 3). The spectroscopic data of our synthetic psamma-
plysene A were identical to those reported for the natural
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Conclusions
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In summary, we have established an improved and efficient
synthesis of psammaplysene A in 50% overall yield from p-
hydroxybenzaldehyde 5 via Knoevenagel condensation and O-
alkylation as key steps. The two major fragments 3 and 4 were
concisely assembled from commercially available p-hydrox-
ybenzaldehyde 5 in ve steps (59%) and tyramine 6 in four steps
(71%), respectively. Our approach is concise and might be
applied in the synthesis of psammaplysene analogues on gram
scale.
¨
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Conflicts of interest
There are no conicts to declare.
Acknowledgements
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This work was supported in part by research grants from
Hangzhou Medical College Foundation (No. 2015B03) and
Natural Science Foundation of Zhejiang Province (No. Y404302).
The authors also thank Dr Saurav Bera for his assistance.
´
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21 E. Garcıa-Egido, J. Paz, B. Iglesias and L. Munoz, Org. Biomol.
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