Asymmetric total synthesis of (+)-isocryptotanshinone and formal synthesis of (−)-cryptotanshinone

Total Syntheses of Strasseriolide A and Strasseriolide B, Potent Antimalarial Agents

We describe the convergent total syntheses of strasseriolides A and B, which are potent antimalarial agents recently isolated from an unnamed plant found in a remote region of New Zealand. Both natural products exhibited potent activity against malaria parasite, Plasmodium falciparum. The synthesis involved asymmetric syn-aldol, asymmetric alkylation, and asymmetric Johnson-Claisen rearrangement to set six of the seven chiral centers of strasseriolide B. The synthesis also highlights the formation of an 18-membered macrolactone from a diacid by using a Yamaguchi macrolactonization protocol. Other key transformations involved Grubbs' cross-metathesis, selective 1,4-reduction, hydrostannylation reaction, and NHK coupling reaction. The convergent synthesis of strasseriolide A required 27 total synthetic steps and 16 longest linear steps from known readily available intermediates.

(+)-Isocryptotanshinone derivatives and its simplified analogs as STAT3 signaling pathway inhibitors

Isocryptotanshinone (ICTS), a natural product with potential signal transducer and activator of transcription-3 (STAT3) signaling pathway inhibitory activity, shows significant inhibitory activity against several tumors. In this study, a series of ICTS derivatives and simplified analogs containing a 1, 4-naphthoquinone core was designed, synthesized, and evaluated. The results demonstrated that most target compounds were potent STAT3 signaling pathway inhibitors based on their mechanism of inhibition of STAT3 phosphorylation. Moreover, based on the obtained data, the structure-activity relationship (SAR) was rationally deduced. Simultaneously, molecular docking of the compound 16r suggested its possible interaction mode with STAT3. To further verify anticancer activity, all target compounds were tested using HCT116, HepG₂, MCF-7, A549, and U251 cell lines. Interestingly, compared with different tumor cell lines, the HCT-116 cell line was determined to be the most sensitive. Furthermore, compounds 21e, 16r, 28a, and 16e showed a dose-dependent inhibition of the growth of HCT116 cells. Thus, the SAR of ICTS derivatives and its simplified analogs was determined, and some of them were discovered to be potential anticancer candidates owing to their ability to inhibit the STAT3 signaling pathway.

Thirteen undescribed diterpenoid quinones derived from the rhizomes of Salvia miltiorrhiza and their anti-tumor activities

Thirteen undescribed diterpenoid quinones were isolated from the dried roots of Salvia miltiorrhiza. Their structures were determined by extensive analysis, including NMR, HRESIMS, and IR. Their absolute configurations were determined by X-ray diffraction, calculated and experimental circular dichroism spectroscopy, and optical rotation. In the evaluation of bioactivities, salviadionether obviously inhibited the proliferation of HCT-116 cells. R-(+)-salmiltiorin E and R-(+)-grandifolia D both showed inhibitory activities on a variety of tumor cells. Salvianone ester A showed strong cytotoxicity to tumor-repopulating cells (TRCs) with an IC₅₀ value of 2.19 μM.

A Relay Strategy Actuates Pre-Existing Trisubstituted Olefins in Monoterpenoids for Cross-Metathesis with Trisubstituted Alkenes

A retrosynthetic disconnection-reconnection analysis of epoxypolyenes-substrates that can undergo cyclization to podocarpane-type tricycles-reveals relay-actuated Δ^6,7-functionalized monoterpenoid alcohols for ruthenium benzylidene catalyzed olefin cross-metathesis with homoprenyl benzenes. Successful implementation of this approach provided several epoxypolyenes as expected (E/Z, ca. 2-3:1). The method is further generalized for the cross-metathesis of pre-existing trisubstituted olefins in other relay-actuated Δ^6,7-functionalized monoterpenoid alcohols with various other trisubstituted alkenes to form new trisubstituted olefins. Epoxypolyene cyclization of an enantiomerically pure, but geometrically impure, epoxypolyene substrate provides an enantiomerically pure, trans-fused, podocarpane-type tricycle (from the E-geometrical isomer).