Synthesis of spongian diterpenes: (−)-spongian-16-oxo-17-al and (−)-acetyldendrillol-1

Abstract An efficient diastereoselective synthesis of the spongian diterpenes (−)-spongian-16-oxo-17-al ( 1 ) and (−)-acetyldendrillol-1 ( 13 ) is described starting from (+)-podocarp-8(14)-13-one ( 6 ) via the ester-dialdehyde 11 as key intermediate. The absolute configuration at C-17 in synthetic compound 13 has conclusively been proved by NOE experiments.

Assignment of1H and13C NMR data for (−)-methyl thyrsiflorin A and some scopadulan precursors

The 1H and 13C NMR spectral analysis of synthetic (−)-methylthyrsiflorin A and 10 scopadulan precursors is reported. Resonance assignments were based on one- and two-dimensional NMR techniques, which included 1H, 13C, DEPT and HMQC and also 1D NOE difference spectroscopy. Copyright © 2001 John Wiley & Sons, Ltd.

1H and13C NMR assignments and conformational analysis of some podocarpene derivatives

This paper reports on the assignment of the 1 Ha nd 13 C NMR spectra of five podocarpene derivatives. Resonance assignments were made on the basis of one- and two-dimensional NMR techniques which included 1 H, 13 C, DEPT and HMQC and also 1D NOE difference spectroscopy. The ratio of the different conformers in the six- membered C-ring of the podocarpene system was determined by molecular mechanics calculations and analysis of proton spin-spin coupling constants. Copyright © 2000 John Wiley & Sons, Ltd.

1H and13C NMR assignments and conformational analysis of some tetracyclic compounds with a bicyclo[4.2.0]octane ring system

Translocation versus cyclisation in radicals derived from N-3-alkenyl trichloroacetamides

Under radical reaction conditions, two different and competitive reaction pathways were observed for N-(alpha-methylbenzyl)trichloroacetamides with a N-3-cyclohexenyl substituent: 1,4-hydrogen translocation and radical addition to a double bond. However, for radicals with an acyclic alkenyl side chain, the direct cyclisation process was exclusively observed. The dichotomy between translocation and direct radical cyclisation in these substrates has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G** computational level.

Fluorescent benzofurazan-cholic acid conjugates for in vitro assessment of bile acid uptake and its modulation by drugs.

One of the most common mechanisms of hepatotoxicity is drug-induced cholestasis. Hence, new approaches for screening the cholestatic potential of drug candidates are desirable. In this context, we describe herein the use of synthetic 4-nitrobenzo-2-oxa-1,3-diazole (NBD) fluorescent conjugates of cholic acid (ChA) at positions 3alpha, 3beta, 7alpha, and 7beta for in vitro assessment of bile acid uptake. All the conjugates show a strong absorption band between 400 and 550 nm and have a fluorescence quantum yield of approximately 0.45, with an emission maximum centered at approximately 530 nm. After their photophysical characterization, 3alpha-, 3beta-, 7alpha-, and 7beta-NBD-ChA were used to …

Synthesis of new, UV-photoactive dansyl derivatives for flow cytometric studies on bile acid uptake.

Four new fluorescent derivatives of cholic acid have been synthesized; they incorporate a dansyl moiety at 3 alpha-, 3 beta-, 7 alpha- or 7 beta- positions. These cholic acid analogs are UV photoactive and also exhibit green fluorescence. In addition, they have been demonstrated to be suitable for studying the kinetics of bile acid transport by flow cytometry.