Asymmetric Total Synthesis of Lepadiformine C Using Memory of Chirality in an Intramolecular Ester Enolate Michael Addition.

The asymmetric synthesis of lepadiformine C was achieved using d-proline as the only chiral source. The synthetic strategy features the use of the principle of "memory of chirality" in an intramolecular Michael addition to construct the bicyclic intermediate without the aid of external chiral sources. A brief mechanistic rationale is presented to account for the stereochemical outcome.

Divergent total synthesis of the tricyclic marine alkaloids lepadiformine, fasicularin, and isomers of polycitorols by reagent-controlled diastereoselective reductive amination.

We describe a flexible and divergent route to the pyrrolo-/pyrido[1,2-j]quinoline frameworks of tricyclic marine alkaloids via a common intermediate formed by the ester-enolate Claisen rearrangement of a cyclic amino acid allylic ester. We have synthesized the proposed structure of polycitorols and demonstrated that the structure of these alkaloids requires revision. In addition to asymmetric formal syntheses, stereoselective and concise total syntheses of (-)-lepadiformine and (-)-fasicularin were also accomplished from simple, commercially available starting materials in a completely substrate-controlled manner.

Design, synthesis, and evaluation of a water-soluble antofine analogue with high antiproliferative and antitumor activity.

New water soluble antofine C-13a analogues were designed, synthesized, and evaluated for antiproliferative activity against cancer cells. Particularly, (-)-(R)-13a-hydroxymethylantofine ((-)-(R)-4b) demonstrated notable growth inhibition against a panel of human cancer cell lines. This growth inhibition was associated with the arrest of the cell cycle in the G0/G1 phases and suppression of mTOR signaling in human lung A549 cancer cells.

Synthesis and anti-platelet activity of obovatol derivatives.

Obovatol derivatives were synthesized and evaluated for anti-platelet activity. Three derivatives (1, 2, 4i) displayed equipotent activity to obovatol in arachidonic acid-induced platelet aggregation. An initial SAR study revealed that the introduction of alkoxy group in B ring could enhance inhibitory activity.

Identification of a potent and noncytotoxic inhibitor of melanin production.

On the basis of a hit from random screening, biaryl amide derivatives were prepared in a combinatorial manner via parallel solution-phase synthesis, and their effects on melanocytes were investigated to discover new effective skin depigmenting agents. Among the 120 derivatives prepared, five members exhibited a >30% reduction of melanin production at 30 microM with a cell viability of >90%. In particular, compound A(3)/B(5) exhibited effective inhibitory activity on melanin synthesis.

Concise synthesis of Obovatol: Chemoselective ortho-bromination of phenol and survey of Cu-catalyzed diaryl ether couplings.

Concise total synthesis of obovatol (1) was achieved from the commercially available eugenol (5) via linear 4 steps in 40% overall yield. The key features of the synthesis involve the chemoselective orthobromination of phenol in the presence of isolated double bond and the efficient Cu-catalyzed Ullmann coupling of two aromatic moieties for the diaryl ether skeleton.

Stereoselective synthesis of (E)- and (Z)-enol ethers from beta-amino aldehydes.

Stereocontrolled methods for the direct and divergent synthesis of the silylenol ethers possessing amino group from beta-amino aldehydes have been achieved. These enol ethers with the defined olefin geometry could be key building blocks for the synthesis of the medicinally impor tant compounds.

Synthesis of novel diaryl ethers and their evaluation as antimitotic agents.

A series of novel diaryl ethers possessing various functional groups were synthesized and evaluated for antiproliferative activity in human myeloid leukemia HL-60 cells. Among the compounds examined, compounds 10, 17, 20, 24, and 33 showed moderate to potent antiproliferative activity. These derivatives were further examined in terms of their abilities to inhibit tubulin polymerization; however, all of the tested compounds were relatively ineffective.