71655-17-9Relevant articles and documents
Conformationally Controlled Linear and Helical Hydrocarbons Bearing Extended Side Chains
Aggarwal, Varinder K.,Butts, Craig P.,Davy, Matthew,Dutton, Oliver J.,Guo, Lin,Kucukdisli, Murat,Myers, Eddie L.,Wagnières, Olivier
, p. 16682 - 16692 (2021/10/21)
Conformationally controlled flexible molecules are ideal for applications in medicine and materials, where shape matters but an ability to adapt to multiple and changing environments is often required. The conformation of flexible hydrocarbon chains bearing contiguous methyl substituents is controlled through the avoidance of syn-pentane interactions: alternating syn-anti isomers adopt a linear conformation while all-syn isomers adopt a helical conformation. From a simple diamond lattice analysis, larger substituents, which would be required for most potential applications, result in significant and unavoidable syn-pentane interactions, suggesting substantially reduced conformational control. Through a combination of computation, synthesis, and NMR analysis, we have identified a selection of substitution patterns that allow large groups to be incorporated on conformationally controlled linear and helical hydrocarbon chains. Surprisingly, when the methyl substituents of alternating syn-anti hydrocarbons are replaced with acetoxyethyl groups, the main chain of almost 95% of the population of molecules adopt a linear conformation. Here, the side chains adopt nonideal eclipsed conformations with the main chain, thus minimizing syn-pentane interactions. In the case of all-syn hydrocarbons, concurrent removal of some methyl groups on the main chain adjacent to the large substituents is required to maintain a high population of molecules adopting a helical conformation. This information can now be used to design flexible hydrocarbon chains displaying functional groups in a defined relative orientation for multivalent binding or cooperative reactivity, for example, in targeting the interfaces defined by disease-relevant protein-protein interactions.
Grubbs Catalysts Immobilized on Merrifield Resin for Metathesis of Leaf Alcohols by using a Convenient Recycling Approach
Xia, Liang,Peng, Tao,Wang, Gang,Wen, Xiaoxue,Zhang, Shouguo,Wang, Lin
, p. 45 - 48 (2019/02/06)
Three new types of heterogeneous catalysts were prepared using a facile approach by the immobilization of Grubbs catalysts on PEGylated Merrifield resin. One of the immobilized catalysts was more efficient than the free catalyst for the metathesis of leaf alcohols in conversion and selectivity and was reused repeatedly (up to 5 cycles) with only a slight loss of activity (10.5 %). The long-chain PEGylated linker provided an appropriate distance between the resin and the catalytic center so that the ruthenium catalysts acted as the free catalyst.
Synthesis of the C18–C26 tetrahydrofuran-containing fragment of amphidinolide C congeners via tandem asymmetric dihydroxylation and SN2 cyclization
Su, Ye-Xiang,Dai, Wei-Min
, p. 1546 - 1554 (2018/02/26)
The C18–C26 fragment of amphidinolide C congeners has been synthesized starting from methyl acetoacetate in 14 steps in >17.0% overall yield. The C20 stereogenic center was secured by asymmetric hydrogenation of a β-keto ester and the configuration at both C23 and C24 was introduced by asymmetric dihydroxylation (AD). The trans-2,5-disubstituted tetrahydrofuran ring was assembled via the tandem AD–SN2 sequence. The latter protocol could be employed for accessing the corresponding cis-2,5-disubstituted tetrahydrofuran rings from the same alkene substrates simply by choosing a suitable AD ligand. Moreover, functional group compatibility was observed for the Ru(II)-catalyzed hydrogenation of β-keto esters and the Pd(0)–Cu(I)-catalyzed Sonogashira cross-coupling reaction. These findings should be valuable for general synthetic design and application.
