Bu-Bing Zeng

Construction of the Isocopalane Skeleton: Application of a Desulfinylative 1,7‐Hydrogen Atom Transfer Strategy

Two attractive chirons, aldehyde 6 and chloride 7, exhibiting functionalized ent-spongiane-type tricyclic skeletons (ABC ring system), have been constructed and their absolute configurations have been studied by NMR spectroscopy and confirmed by single-crystal X-ray diffraction. Both of these chirons are derived from commercially available andrographolide in good yield. Aldehyde 6 is obtained through a novel K2 S2 O8 -catalyzed aquatic ring-closing reaction of allylic sodium sulfonate and intramolecular 1,7-hydrogen atom transfer process. Further mechanistic investigations demonstrate that the 1,7-hydrogen atom transfer is a free-radical process, whereby hydrogen migrates from C18 to C17, as evidenced by double-18- deuterium-labeled isotope experiments. Prospective applications of these two chiral sources are also discussed.

Synthesis of the scalarane sesterterpenoid 16-deacetoxy-12-epi-scalarafuranacetate.

The marine natural product 16-deacetoxy-12-epi-scalarafuranacetate, isolated from Spongua officinalis , was synthesized in 18 linear steps, starting from (-)-sclareol, with high stereoselectivity and an overall yield of 6.1%. The intermediate 16-deacetoxy-12-epi-scalarafuran could be easily transformed into a series of natural scalarane sesterterpenoids in a few steps.

Apoptosis induction of ZBB-006, a novel synthetic diterpenoid, in the human hepatocellular carcinoma cell line HepG2 in vitro and in vivo.

Diterpenes, present in many medicinal plants, have been the focus of continuous studies for the development of new anticancer agents. ZBB-006 is a new synthetic diterpenoid derivative which exhibited significant anti-proliferation activity against various cancer cell lines in our previous study. Here, we investigated the antitumor effect of ZBB-006 and its potential mechanisms in the human hepatocellular carcinoma cell line HepG2, both in vitro and in vivo. We found that oral administration of ZBB-006 effectively suppressed the growth of HepG2 xenograft tumor in nude mice without body weight decline, compared with the control group. Meanwhile, the growth inhibitory effect of ZBB-006 on HepG2 cells was observed with MTT assay. Then apoptosis induced by ZBB-006 in HepG2 cells was evidenced by DAPI staining and Annexin V/PI double staining assay. ZBB-006 also dissipated the mitochondrial membrane potential (∆Ψm) apparently as revealed by JC-1 staining. Furthermore, the cleavage of PARP, activation of caspase-3 and caspase-9 but not caspase-8 was demonstrated by Western blot assay both in vitro and in vivo. Additionally, the proapoptotic protein Bax was markedly elevated, while the antiapoptotic protein Bcl-2 was down-regulated. Collectively, our data indicated that ZBB-006 exerted a strong antitumor effect on HepG2 cells by initiating the mitochondrial-dependent apoptosis, and it has potential to be explored as a new promising therapeutic agent against human hepatoma.

Straightforward synthesis of two pairs of enantiomeric butenolides 3-tetradecyl- and 3-hexadecyl-5-methyl-2(5H)-furanone.

Based on the synthetic method of optically active 3-alkyl-5-methyl-2(5H)-furanones from lactic acid, two pairs of chiral butenolides 3-tetradecyl- and 3-hexadecyl-5-methyl-2(5H)-furanone have been straightforwardly synthesized from methyl stearate and methyl palmitate respectively by aldol condensation with (R)- or (S)-O-tetrahydropyranyl lactal prepared from corresponding ethyl lactate and beta-elimination.