Application of Enantioselective Radical Reactions: Synthesis of (+)-Ricciocarpins A and B
摘要:
Enantioselective synthesis of (+)-ricciocarpins A and B has been achieved in 41 and 45% overall yields, respectively, starting from a beta-substituted oxazolidinone. The key steps in the strategy are an enantioselective conjugate radical addition and the addition of a furyl organometallic to a key aldehyde intermediate.
Small rings through large templates: A two‐point binding of the substrate radicals to cationic titanocene templates is essential for the success of otherwise impossible 4‐exo cyclizations (see scheme; Bn=benzyl). The cyclobutanes are obtained in high stereoselectivity and can be additionally functionalized in a straightforward manner.
The first example of a catalytic enantioselective intramolecular hydride shift/ring closure reaction is reported. This redox neutral reaction cascade allows for the efficient formation of ring-fused tetrahydroquinolines in high enantioselectivities.
An enantioselective desymmetrisation approach to C9-substituted trans-hydrindene rings based on a diastereotopic group-selective intramolecular Diels–Alder reaction
作者:Nadia Azzi、Ed Griffen、Mark Light、Bruno Linclau
DOI:10.1039/b607488j
日期:——
The synthesis of an achiral skipped bis(1,3-diene) substrate was achieved, which was shown to undergo an enantioselective, diastereotopic group-selective, intramolecular Diels-Alder reaction.
Synthesis of Highly Oxygenated Bicyclic Carbasugars. Remarkable Difference in the Reactivity of the d-gluco and d-xylo- Derived Trienes
作者:Grzegorz Witkowski、Mykhaylo A. Potopnyk、Karolina Tiara、Anna Osuch-Kwiatkowska、Sławomir Jarosz
DOI:10.3390/molecules25153357
日期:——
2,3,4-Tri-O-benzyl-D-xylopyranose was used as a starting material in the preparation of the corresponding triene, which underwent smooth cyclization to a polyhydroxylated hydrindane, as a single diastereoisomer. The analogous triene prepared from D-glucose did not undergo any cyclization even under high pressure.
A novel approach to the synthesis of (±)-fragranol is described that relies on a radical 4-exo cyclization. This key step is catalyzed by a cationic titanocene complex with a pending amide ligand. In this manner the radical and its acceptor are bound to the titanocene center in a two-point mode. By this interaction the 4-exo cyclization that is not supported by gem-dialkyl substitution is rendered