A highly enantioselective polycyclization method has been developed using the combination of Lewis acid activation with iridium-catalyzed allylic substitution. This strategy relies on direct use of branched, racemic allylic alcohols and furnishes a diverse and unique set of carbo- and heteropolycyclic ring systems in good yields and >= 99% ee.
Total Synthesis of (±)-Cafestol: A Late-Stage Construction of the Furan Ring Inspired by a Biosynthesis Strategy
作者:Lili Zhu、Jisheng Luo、Ran Hong
DOI:10.1021/ol500623w
日期:2014.4.18
aldehyde–ene cyclization and subsequent Friedel–Crafts reaction deliver a requisite tricyclic system in gram scale with high stereo- and regioselectivity. Moreover, a highly stereoselective SmI2-mediated aldehyde–alkene radical cyclization furnishes the key bicyclo[3.2.1]octane skeleton to offer an advanced intermediate for the synthesis of other oxygenated ent-kaurene diterpenoids.
Lewis Acid Catalyzed Intramolecular Diels−Alder Reactions of Acyclic (<i>Z</i>)-Substituted 1,3-Dienes
作者:Neal A. Yakelis、William R. Roush
DOI:10.1021/ol015667k
日期:2001.3.1
Lewis acid catalyzed intramolecular Diels-Alder reactions of trienes (E,E,Z)-1a-d, (E,E,Z)-4a-d, and (E,Z,Z)-7a,b are described. Trienes containing enal or enone dienophiles cyclize in excellent yield under mild conditions using substoichiometric amounts of MeAlCl(2), in most cases with high levels of diastereoselectivity. The thermal IMDA reactions of 1a, 4a, and 7a require forcing conditions and
Synthesis of Non-natural, Frame-Shifted Isoprenoid Diphosphate Analogues
作者:Kayla J. Temple、Elia N. Wright、Carol A. Fierke、Richard A. Gibbs
DOI:10.1021/acs.orglett.6b02977
日期:2016.12.2
A set of synthetic approaches was developed and applied to the synthesis of eight frame-shifted isoprenoid diphosphate analogues. These analogues were designed to increase or decrease the methylene units between the double bonds and/or the pyrophosphate moieties of the isoprenoid structure. Evaluation of mammalian GGTase-I and FTase revealed that small structural changes can result in substantial changes
Remarkable Phosphine-Effect on the Intramolecular Aldol Reactions of Unsaturated 1,5-Diketones: Highly Regioselective Synthesis of Cross-Conjugated Dienones
作者:Reema K. Thalji、William R. Roush
DOI:10.1021/ja054085l
日期:2005.12.1
We report a phosphine-mediated intramolecular aldolcyclization of unsaturated diketones that proceeds with extremely high levels of regioselectivity for the cross-conjugated bicyclic dienone products. The sense of regioselectivity observed in this reaction is complementary to that obtained using traditional aldol conditions. Experimental evidence that supports the involvement of a phosphine Michael