The latter showed only μ M antiproliferative activity, thus being several hundred-fold less potent than 1. Oxidation of the aldehyde functionality of ent- 2 gave a carboxylic acid that was converted into the corresponding N-hexyl amide. The same activity level was attained by the monocyclic desTHP derivative of 1. Each month, select sellers offer their items for sale on AbeBooks. The choice of used books is massive - from classic novels to childrens books, and so much more. Giving used books new life is what we do best. 13-Desmethylene- ent- 2 as well as the reduced versions of ent- 2 and 13-desmethylene- ent- 2 all showed similar cellular activity as ent- 2 itself. Fill your bookshelves with used books, the latest bestsellers, collectible books and forgotten out-of-print titles from years gone by. Synthetic 1 inhibited human cancer cell growth in vitro with n M IC 50 values, while ent- 2, which lacks the diene-containing hemiaminal-linked side chain of 1, is 25- to 260-fold less active. Employing the same overall strategy, 13-desmethylene- ent- 2 as well as the monocyclic desTHP derivatives of 1 and ent- 2 were prepared. THP ring formation was accomplished through a segment coupling Prins-type cyclization. The β-keto phosphonate/aldehyde precursor for the ring-closure reaction was obtained by esterification of a ω-diethylphosphono carboxylic acid fragment and a secondary alcohol fragment incorporating the THP ring that is embedded in the macrocyclic core structure of 1 and ent- 2. The synthesis features a high-yielding, selective intramolecular Horner–Wadsworth–Emmons (HWE) reaction to close the 20-membered macrolactone ring of 1 and ent- 2. A new total synthesis of the marine macrolide (−)-zampanolide ( 1) and the structurally and stereochemically related non-natural levorotatory enantiomer of (+)-dactylolide ( 2), that is, ent- 2, has been developed.
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