- Diastereoselective Synthesis of Highly Substituted Tetrahydrofurans by Pd-Catalyzed Tandem Oxidative Cyclization-Redox Relay Reactions Controlled by Intramolecular Hydrogen Bonding
-
Palladium-catalyzed oxidative cyclization of alkenols provides a convenient entry into cyclic ethers but typically proceeds with little or no diastereoselectivity for cyclization of trisubstituted olefins to form tetrahydrofurans due to the similar energi
- Brooks, Joshua L.,Xu, Liping,Wiest, Olaf,Tan, Derek S.
-
supporting information
p. 57 - 75
(2017/04/26)
-
- Squalene-hopene cyclase: Insight into the role of the methyl group on the squalene backbone upon the polycyclization cascade. Enzymatic cyclization products of squalene analogs lacking a 26-methyl group and possessing a methyl group at C(7) or C(11)
-
To provide deep insight into the polycyclization reaction of squalene, some analogs were synthesized and incubated with the cell-free homogenates of the recombinant Escherichia coli encoding the wild-type squalene cyclase. The presence of C(6)-Me leads to an efficient polycyclization cascade. Substitution of the C(14)-H and the C(18)-H with a methyl group halted the polycylization reaction at the tricyclic ring stage having a 6/6/6-fused ring system and the tetracycle with a 6/6/6/6-fused ring, respectively, both of which were produced according to a Markovnikov closure. Replacement of the C(7)-H and the C(11)-H with a methyl group led to no cyclization. These results, in conjunction with our previous reports, indicated that the methyl positions are important for bringing to completion of the normal polycylization reaction and further demonstrated that the precise steric bulk size at the methyl positions of squalene is critical to the correct folding and the strong binding of the substrate to the squalene cyclase.
- Nakano, Shin-Ichi,Ohashi, Shumi,Hoshino, Tsutomu
-
p. 2012 - 2022
(2007/10/03)
-
- Microwave Heating Effects Rapid and Selective Decarboalkoxylation of Mono-Alkylated Malonates and β-Ketoesters
-
Brief microwave irradiation of mono-alkylated malonates and β-ketoesters at 160-200 °C in wet DMF induces smooth and selective decarboalkoxylation. Observations suggest that this reaction occurs by nucleophilic attack of water at the ester carbonyl carbon (hydrolysis) followed by decarboxylation of the resulting acid. The process occurs despite the absence of traditional acid, base or nucleophile catalysts or reagents.
- Curran, Dennis P.,Zhang, Qisheng
-
p. 329 - 332
(2007/10/03)
-
- AN EFFICIENT ROUTE TO TRIENE SYNTHONS FOR PUTATIVE INTERMEDIATES IN POLYETHER ANTIBIOTIC BIOSYNTHESIS
-
Current research to establish the late stages of polyether antibiotic biosynthesis via polyepoxide cyclization cascades, as formulated by Cane, Celmer, and Westley, requires the availability through synthesis of relevant putative triene intermediates.The
- Dyer, Ulrich C.,Robinson, John A.
-
-