Where is the Oxygen? Structural Analysis of α‐Humulene Oxidation Products by the Crystalline Sponge Method

Abstract

Crystal structures of a-humulene,acyclic sesquiterpene,a nd its oxidized subproducts,w ere analyzed by the crystalline sponge method. Regio-and stereochemistry,including absolute configuration when achiral oxidant was applied, and the stable conformations of all the scaffold-related compounds were successfully determined for samples on a 5-50 mgscale.

Biomimetic Total Synthesis of Hyperjapones A–E and Hyperjaponols A and C

“…As tereospecific 1,2-alkyl shift of secondary Alternatively,i ti sp erhaps more likely that carbocation 14 would directly rearrange to give carbocation 16 through ac oncerted, asynchronous alkene cyclization/1,2-alkyl shift. As expected from molecular modelling studies and Fujitas humulene epoxidation work, [8] treatment of 1 with m-CPBAg enerated epoxide 13 as as ingle diastereomer in 76 %yield through diastereoselective oxidation of the D 8,9 alkene.W ew ere then delighted to observe that acid-Scheme 1. [9] Theprimary aim of this project was to use the biosynthetic hypothesis outlined in Scheme 1a st he blueprint for ad ivergent, biomimetic synthesis of hyperjaponols A-C (6-8)f rom hyperjapone A( 1).…”

“…Further racemic natural products,hyperjaponols A-C [2] (6)(7)(8), have also been isolated from Hypericum japonicum.T he most structurally intriguing of these natural products is hyperjaponol C( 8)b ecause its stereochemically complex, but racemic, trans-isodaucane framework implies ah ighly predisposed, non-enzymatic biosynthesis. Further racemic natural products,hyperjaponols A-C [2] (6)(7)(8), have also been isolated from Hypericum japonicum.T he most structurally intriguing of these natural products is hyperjaponol C( 8)b ecause its stereochemically complex, but racemic, trans-isodaucane framework implies ah ighly predisposed, non-enzymatic biosynthesis.…”

“…Hyperjapones B-E (2-5)c ould arise from as imilar nonenzymatic, oxidative hetero-Diels-Alder reaction between atrimethylated acylphloroglucinol and the reactive trans D 4,5 alkene of caryophyllene (18). [8] Acid-catalyzed ring opening of epoxide 13 would generate tertiary carbocation 14,w ith the carbocation centered at the C9 position. [1] Diastereoselective epoxidation of the exposed face of the D 8,9 alkene would therefore give epoxide 13,w hich has a1 R*2R*8S*9S*r elative configuration.…”

Bis‐Calix[4]arenes: From Ligand Design to the Directed Assembly of a Metal–Organic Trigonal Antiprism

“…This activity stemsp artly from the chemist's desire to understand the self-assembly of complex multi-component architectures, [1] but also from the fact that the resultinga ssemblies can be discrete [1] or polymeric [2] in nature,p ossessing targeted physical properties [3] or finding utility in aw ide variety of areas such as catalysis, [4] controlled guest uptake/release [5] and novelc rystallisation media. [6] Strategies for directeda ssemblyt ypically rely on the use of both coordination templates and ligand design, [7] the latter being the general focuso ft his contribution.…”

“…The [Mn III 2 Mn II 2 (C[4]) 2 ]s ingle-molecule magnet (SMM) [9b] was selected as the standardt est system to see if this would form without the xylyl-tether constraints discussed above.R eaction between benzyl-C [4] and manganese(II) chloride hydrate in aD MF/MeOH mixture and in the presence of triethylamine afforded ad ark purple solution from whichs ingle crystals grew upon vapour diffusion with acetonitrile. The crystalsw ere in at riclinic cell and structural studies found them to be [Mn III 2 Mn II 2 (benzyl-C[4]) 2 (OH) 2 (DMF) 6 ]·(MeOH) 0.6 (MeCN) 1.4 , 4,w ith structure solution being performedi nt he space group P-1. The asymmetric unit (ASU)c omprises one half of the expected Mn III 2 Mn II 2 butterfly-like cluster and symmetry generation Figure 1A).…”