Ergopeptides, like ergocornine and α-ergocryptine, exist in an Sand in an R-configuration. Kinetic experiments imply that certain configurations are preferred depending on the solvent. The experimental methods are explained in this article. Furthermore, computational methods are used to understand this configurational preference. Standard quantum chemical methods can predict the favored configu...

The preparation of an advanced intermediate toward the enantioselective synthesis of tetrodotoxin is outlined. The enantiomerically pure cyclopentene 15 was generated from ketone 14 by alkylidene carbene insertion with retention of absolute configuration. An ozonolysis/aldol sequence first produced the trans cyclohexenone, which upon epimerization gave the more stable cis enone 18.

The conversion from kobophenol A into carasinol B, two main chemical constituents of Caragana sinica, was confirmed by in vitro acid-catalyzed epimerization. The result provides important information about the biotransformation of kobophenol A in plants and its metabolism in rats.

The catalytic enantioselective 6-exo-trig Michael addition-lactonization of enone-acid substrates to form cis-chromenones with high diastereo- and enantiocontrol was developed using the commercially available isothiourea tetramisole. An acidic workup proved necessary to minimize product epimerization and maximize product er, providing cis-chromenones in excellent yield, and with excellent diast...

By studying its C4 epimer α-D-galactose, the effects of epimerization on the conformational behaviour of α-D-glucose have been unveiled. Using laser ablation of crystalline samples, four conformers of α-D-galactopyranose have been observed, for the first time, in a supersonic expansion by analyzing the Fourier transform rotational spectrum.

[reaction: see text] The weak base lithium 1,1,1,3,3,3-hexafluoroisopropoxide (LiHFI) is shown to be highly effective as a reagent for intermolecular Horner-Wadsworth-Emmons (HWE) olefination of epimerizable aldehydes with trimethyl phosphonoacetate, affording products with little or no epimerization and notably high E-selectivity.

The key tricyclic intermediate 3a, for the total synthesis of the C(20)-nor analogue of salvinorin A, was prepared in seven steps from 3-furaldehyde. Key steps involved a highly regio- and diastereoselective Lewis acid assisted Diels-Alder reaction followed by base-promoted epimerization and a completely stereoselective conjugate reduction.

We describe herein a concept of optical memory using a photosensitive metal complex, [Cr((-)-tfac)3] ((-)-tfac = (-)-3-trifluoroacetylcamphorato), as a dopant to induce chiral nematic phases. The memory was written by the photo-epimerization of the complex and read-out in terms of circular dichroism spectra. The rewritability of the memory was attempted by using the cycles between liquid crysta...