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401.
Barry M. Trost Jacob S. Tracy Tas Yusoontorn Chao‐I Joey Hung 《Angewandte Chemie (International ed. in English)》2020,59(6):2370-2374
The preparation of acyclic β‐fluoro amines bearing tetrasubstituted fluorine stereocenters is described via a direct Zn/ProPhenol‐catalyzed Mannich reaction. The reaction utilizes branched vinyl or alkynyl α‐fluoro ketones that can be coupled with a range of aryl, heteroaryl, vinyl, or cyclopropyl aldimines in high yield and with excellent diastereo‐ (up to >20:1) and enantioselectivity (up to 99 %). The use of readily cleaved tert‐butoxycarbonyl (Boc) or carboxybenzyl (Cbz) imine protecting groups adds utility to the reaction by allowing for easy access to the free amine products under mild and chemoselective reaction conditions. 相似文献
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A convenient access to substituted allyl enol carbonates was established through the reaction of ketone enolates with the complex of allyl 1H-imidazole-1-carboxylates and boron trifluoride etherate. 相似文献
404.
Rhodium-catalyzed oxidative cyclization of allylic hydroxylamine-derived sulfamate esters furnishes a novel family of bicyclic aziridines that serve as functional precursors to substituted diamines. Investigations with the N4-Troc form of these heterocycles have led to manifold improvements in reaction performance and scope and have revealed unique differences in the stability and reactivity of such compounds dictated by the choice of N4-protecting group. 相似文献
405.
Enabled by the broad scope of the Pd-catalyzed asymmetric alkylation of meso- and d,l-divinylethylene carbonate, several chiral diene ligands were prepared in two steps from commercial materials. Subsequently, these ligands were evaluated in the Rh-catalyzed asymmetric conjugate addition of boronic acids to enones. 相似文献
406.
Trost BM Frontier AJ Thiel OR Yang H Dong G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(35):9762-9776
Bryostatins, a family of structurally complicated macrolides, exhibit an exceptional range of biological activities. The limited availability and structural complexity of these molecules makes development of an efficient total synthesis particularly important. This article describes our initial efforts towards the total synthesis of bryostatins, in which chemoselective and atom-economical methods for the stereoselective assembly of the ring C subunit were developed. A Pd-catalyzed tandem alkyne-alkyne coupling/6-endo-dig cyclization sequence was explored and successfully pursued in the synthesis of a dihydropyran ring system. Elaboration of this methodology ultimately led to a concise synthesis of the ring C subunit of bryostatins. 相似文献
407.
Herein, we report the synthesis of novel ring-expanded bryostatin analogues. By carefully modifying the substrate, a selective and high-yielding Ru-catalyzed tandem enyne coupling/Michael addition was employed to construct the northern fragment. Ring-closing metathesis was utilized to form the 31-membered ring macrocycle of the analogue. These ring-expanded bryostatin analogues possess anticancer activity against several cancer cell lines. Given the difficulty in forming the C16-C17 olefin at a late stage, we also describe our development of a new-generation strategy to access the C7-C27 fragment, containing both the ring B and C subunits. 相似文献
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