The first total synthesis of (S)-clavulazine from d-mannitol

Direct Crystallization Resolution of Racemates Enhanced by Chiral Nanorods: Experimental, Statistical, and Quantum Mechanics/Molecular Dynamics Simulation Studies

Three chiral nanorods of C14-l-Thea, C14-l-Phe, and C14-d-Phe were first synthesized and utilized as heterogeneous nucleants to enhance the resolution of racemic Asp via direct crystallization. Through the statistical analysis from 320 batches of nucleation experiments, we found that the apparent appearance diversity of two enantiomeric crystals of Asp existed in 80 homogeneous experiments without chiral nanorods. However, in 240 heterogeneous experiments with 4.0 wt % chiral nanorods of solute mass added, the appearance of those nuclei with the same chirality as the nanorods was apparently promoted, and that with the opposite chirality was totally inhibited. Under a supersaturation level of 1.08, the maximum ee of the initial nuclei was as high as 23.51%. When the cooling rate was 0.025 K/min, the ee of the product was up to 76.85% with a yield of 14.41%. Furthermore, the simulation results from quantum mechanics (QM) and molecular dynamics (MD) revealed that the higher chiral recognition ability of C14-l-Thea compared to C14-l-Phe that originated from the interaction difference between C14-l-Thea and Asp enantiomers was larger than that between C14-l-Phe and Asp enantiomers. Moreover, the constructed nanorods exhibited good stability and recyclability.

Recent applications in natural product synthesis of dihydrofuran and -pyran formation by ring-closing alkene metathesis

Examples from 2003 to 2015 of ring-closing alkene metathesis (RCM) in the generation of dihydro-furans or -pyrans for natural product synthesis, are reviewed.

Marine natural products

This review covers the literature published in 2006 for marine natural products, with 758 citations (534 for the period January to December 2006) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidaria, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (779 for 2006), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.