Herein, we report
a Rh(II)-catalyzed reaction between 1-tosyl-1,2,3-triazoles
and halohydrins to provide 2,6-substituted 3,4-dihydro-2H-1,4-oxazines under basic conditions. The reaction is proposed to
undergo a rhodium carbenoid 1,3-insertion into O–H followed
by an annulation. The scope includes phenyl or alkenyl C4-substituted
triazoles and a range of halohydrins using catalytic Rh2Oct4 and K2CO3. A synthesis of the
antimicrobial natural product (±)-chelonin C is also reported
using this novel methodology.
Substituted morpholine derivatives appear frequently in biologically active compounds and thus novel routes towards such structures are of great synthetic interest. Herein, we report the total syntheses of chelonin A, a morpholine-derived marine natural product with reported antibacterial and anti-inflammatory activity. The key step in this process was a rhodium carbenoid 1,3-insertion into a bromohydrin O−H bond, followed by annulation, leading to a 2,6-disubstituted-3,4-dihydro-2H-1,4-oxazine core. This work was then extended to deliver the first asymmetric total synthesis of (−)-chelonin A using an enantioenriched bromohydrin prepared in-turn via asymmetric transfer hydrogenation of an -bromoketone.
Description
Twenty-one peer reviewed papers give you the latest research and technical developments in the medical uses of stainless steels. It covers a wide range of topics, including corrosion, wear, biological response, radiopacity, and the high cost of medical products. New alloys are discussed as solutions to some issues by offering more biocompatible, higher quality, radiopaque, or low cost alternatives for orthopaedic implants and stents. Several corrosion papers address this key concern for all medical devices, while others offer creative options for this field. Timely issues, such as injuries due to the interaction of implants and MRI examinations are also addressed.
Audience: This new publication is a valuable resource for materials scientists and engineers, medical device development engineers, medical doctors and surgeons, metallurgists; medical researchers, medical device R&D managers, and stainless steel manufacturing engineers.
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