10.1021/jo050747d
The research explores the development of an asymmetric version of the decarboxylative Claisen rearrangement (dCr) reaction using sulfoximine-substituted allylic acetate esters. The purpose of the study is to achieve high diastereoselectivity in the dCr reaction by introducing chiral sulfoximines as surrogates for sulfones. The researchers synthesized various esters containing N-arylsulfonyl sulfoximines and subjected them to the dCr reaction, achieving diastereoselectivities up to 82:18. Key chemicals used include N-(2,4,6-triisopropylphenylsulfonyl)-S-phenyl sulfoximine, which provided the best selectivity, and reagents like N,O-bis(trimethylsilyl)acetamide (BSA) and potassium acetate (KOAc) for facilitating the reaction. The study concludes that the stereochemical outcome of the rearrangement can be rationalized by a pseudochair transition-state model, with the stereochemistry of the major isomers confirmed by X-ray crystallography. The results suggest that further modifications to the system, such as adding more electron-withdrawing groups, could enhance selectivity and lower reaction temperatures.
10.1016/S0960-894X(01)00110-X
The research focuses on the synthesis and hybridization properties of a 9-mer adenine derivative of α-L-LNA (α-L-ribo configured locked nucleic acid), which is a type of nucleic acid mimic designed to have superior properties such as increased stability towards nucleolytic degradation and enhanced binding affinity and specificity towards complementary nucleic acid targets. The study successfully developed a synthetic route for the first α-L-LNA purine monomer, involving the synthesis of a bicyclic adenine nucleoside through a condensation reaction between l-threo-pentofuranose derivative and 6-N-benzoyladenine, followed by C20-epimerization and cyclization. The synthesized α-L-LNA monomers were then incorporated into a 9-mer oligonucleotide, which demonstrated high-affinity hybridization with complementary DNA, RNA, LNA, and α-L-LNA target sequences. The chemicals used in the process included 6-N-benzoyladenine, SnCl4, TMS-triflate, N,O-bis(trimethylsilyl)acetamide, mesyl chloride, sodium hydride, and various other reagents for protection, deprotection, and purification steps. The conclusions of the research were that the α-L-LNA monomers, particularly the adenine derivatives, significantly enhance the affinity of the resulting oligonucleotides for their complementary sequences, and that α-L-LNA:α-L-LNA and α-L-LNA:LNA duplexes form exceptionally stable structures, comparable to LNA:LNA duplexes.