EXPLORATION OF BRAVERMAN REACTION CHEMISTRY. SYNTHESIS OF TRICYCLIC DIHYDROTHIOPHENE DIOXIDE DERIVATIVES FROM BISPROPARGYL SULFONES

Benzo-Fused 7-Oxabicyclo[2.2.1]heptane-2,3-diol Derivatives as Universal Linkers for Solid-Phase Oligonucleotide Synthesis

In solid-phase oligonucleotide (ON) synthesis, especially for 3′-modified ONs, a universal linker attached to a solid support is widely used. In this study, benzo-fused 7-oxabicyclo[2.2.1]heptane-2,3-diol derivatives are designed, synthesized, and evaluated as universal linkers. The designed linkers show reactivity comparable to that of a conventional universal linker for releasing the desired ONs. Additionally, these materials exhibit a more robust structure under basic conditions, as generally used in ON synthesis, and hydrophobic properties relative to the conventional universal linker. Notably, when diphenyl-substituted (terphenyl) and phenanthrene-type (PT) linkers are used, cyclic phosphodiesters derived from linker units as byproducts, which are produced by release of ONs from the linker units, are detected in the HPLC chromatograms. The PT linker is applicable to various ON syntheses using controlled pore glass (CPG) and polystyrene (PS) resins. These results demonstrate that the PT linker can serve as an alternative to conventional universal linkers.

Cytotoxic Alkylynols of the Sponge Cribrochalina vasculum: Structure, Synthetic Analogs and SAR Studies

A series of twenty-three linear and branched chain mono acetylene lipids were isolated from the Caribbean Sea sponge Cribrochalina vasculum. Seventeen of the compounds, 1–17, are new, while six, 18–23, were previously characterized from the same sponge. Some of the new acetylene-3-hydroxy alkanes 1, 6, 7, 8, 10 were tested for selective cytotoxicity in non-small cell lung carcinoma (NSCLC) cells over WI-38 normal diploid lung fibroblasts. Compound 7, presented clear tumor selective activity while, 1 and 8, showed selectivity at lower doses and 6 and 10, were not active towards NSCLC cells at all. The earlier reported selective cytotoxicity of some acetylene-3-hydroxy alkanes (scal-18 and 23), in NSCLC cells and/or other tumor cell types were also confirmed for 19, 20 and 22. To further study the structure activity relationships (SAR) of this group of compounds, we synthesized several derivatives of acetylene-3-hydroxy alkanes, rac-18, scal-S-18, R-18, rac-27, rac-32, R-32, S-32, rac-33, rac-41, rac-42, rac-43, rac-45, rac-48 and rac-49, along with other 3-substituted derivatives, rac-35, rac-36, rac-37, rac-38, rac-39 and rac-40, and assessed their cytotoxic activity against NSCLC cells and diploid fibroblasts. SAR studies revealed that the alcohol moiety at position 3 and its absolute R configuration both were essential for the tumor cell line selective activity while for its cytotoxic magnitude the alkyl chain length and branching were of less significance.

Synthesis of bioactive speciosins G and P from Hexagonia speciosa

The first total synthesis of speciosins P and G, previously isolated from Hexagonia speciosa, is reported. These compounds have been synthesized by Sonogashira coupling from readily available starting materials. Siccayne was also synthesized from the same starting material in two steps along with a number of other derivatives. The compounds were tested in the wheat coleoptile bioassay. The most active compound was the intermediate 18, followed by 29 and 17. The structural requirements for activity in these compounds are the presence of methoxy groups in the aromatic ring and a formyl or hydroxy group in the side chain.

Total Synthesis of (±)-Dragmacidin E: Problems Solved and Lessons Learned

(±)-Dragmacidin E was synthesized in 25 steps from commercially available 7-(benzyloxy)indole. Key transformations in this sponge metabolite's preparation include (a) a Witkop cyclization to establish the bridging indole core, (b) cyclo-dehydrative pyrazinone formation to unite the two indole-bearing components, and (c) late-stage guanidine installation via chemoselective carbonyl activation.