Elatenyne is a small dibrominated natural product first isolated from Laurencia elata. The structure of elatenyne was originally assigned as a pyrano[3,2-b]pyran on the basis of NMR methods. Total synthesis of the originally proposed pyrano[3,2-b]pyran structure of elatenyne led to the gross structure of the natural product being reassigned as a 2,2'-bifuranyl. The full stereostructure of this highly flexible small molecule was subsequently predicted by Boltzmann-weighted DFT calculations of (13)C NMR chemical shifts for all 32 potential diastereomers, with the predicted structure being in accord with the proposed biogenesis outlined below. Herein we report two complementary total syntheses of elatenyne, which confirm the computer-predicted stereostructure. Additionally, the total syntheses of (E)-elatenyne and a related 2,2'-bifuranyl, laurendecumenyne B, are reported. This work has not only allowed the full structure determination of all of these natural products but also provides excellent supporting evidence for their proposed biogenesis. The total synthesis of elatenyne demonstrates that DFT calculations of (13)C NMR chemical shifts coupled with biosynthetic postulates, comprise a very useful method for distinguishing among large numbers of highly flexible, closely related molecules.

Most genome-wide association studies are based on samples of European descent. We assess whether the genetic determinants of blood lipids, a major cardiovascular risk factor, are shared across populations. Genetic correlations for lipids between European-ancestry and Asian cohorts are not significantly different from 1. A genetic risk score based on LDL-cholesterol-associated loci has consistent effects on serum levels in samples from the UK, Uganda and Greece (r = 0.23–0.28, p < 1.9 × 10−14). Overall, there is evidence of reproducibility for ~75% of the major lipid loci from European discovery studies, except triglyceride loci in the Ugandan samples (10% of loci). Individual transferable loci are identified using trans-ethnic colocalization. Ten of fourteen loci not transferable to the Ugandan population have pleiotropic associations with BMI in Europeans; none of the transferable loci do. The non-transferable loci might affect lipids by modifying food intake in environments rich in certain nutrients, which suggests a potential role for gene-environment interactions.

The enantioselective synthesis of (+)-laurencin 1 has been achieved in 27 steps from (R)-malic acid 20.The key steps involved methylenation of the lactone 49 followed by intramolecular hydrosilation of the enol ether 14 (Scheme 11) and one carbon homologation of the diol 13 to give the key ethyl substituted cyclic ether 59 (Scheme 13). The lactone 49 was obtained by two efficient routes, namely a Claisen ring expansion (Scheme 3) followed by R-hydroxylation (Scheme 6) and a Yamaguchi lactonization (Scheme 11). Elaboration of the (E)-pentenynyl side chain (Scheme 18) and introduction of bromine (Scheme 19) completed the synthesis of (+)-laurencin 1. Scheme 2. Retrosynthesis of (+)-Laurencin 1

We have studied the proline-directed, Pd-catalyzed enantioselective hydrogenation of isophorone in the liquid state using a variety of methods. Our results unambiguously reveal the true reaction pathway and demonstrate that all earlier mechanistic hypotheses are wrong: although a proline/isophorone condensation product is formed, it is merely a spectator and not a key reaction intermediate in subsequent heterogeneous hydrogenation. Enantioselectivity is the result of kinetic resolution-a process that occurs homogeneously in solution and not at the metal surface. Racemic 3,3,5-trimethylcyclohexanone (TMCH) is produced by initial heterogeneous hydrogenation of isophorone; proline then reacts homogeneously, preferentially with one enantiomer of TMCH, leaving an excess of the other. Thus in complete contrast to the case of ketoester asymmetric hydrogenation, the metal surface is not involved in the crucial enantio-differentiation step. The mechanism we propose also explains why the maximum attainable yield of enantiopure TMCH cannot exceed 50%.

The stereochemistry of conformationally mobile five-membered rings is often hard to assign from NMR data, and [2,2']bifuranyl systems are even more challenging. GIAO (13)C NMR chemical shifts have been calculated for a series of [2,2']bifuranyl and pyranopyran species, taking into account their conformational flexibility using weighted averages of the data for all low energy conformers. We show that calculation of (13)C NMR chemical shifts using the geometries obtained using molecular mechanics greatly reduces the computational expense without a significant loss of accuracy, even in this demanding system. The results were sufficiently accurate to distinguish not only the pyran and furanyl isomers but also between all the diastereoisomeric forms. As a result of this validation, we predict the stereochemistry for the recently proposed revised structure of the natural product elatenyne, which contains a [2,2']bifuranyl core.