Oxazoline N-Oxide-Mediated [2 + 3] Cycloadditions: Application to a Total Synthesis of the Hypocholesterolemic Agent 1233A
摘要:
Oxetanone 1233A1 has been synthesized in 22 steps and 3.43% overall yield from 3-methylglutaric anhydride. Asymmetric carbon at C-7 was introduced by a diastereoselective esterification of 3-methylglutaric anhydride, whereas the two asymmetric carbons at C-2' and C-3' were controlled by an asymmetric [2 +/- 3] cycloaddition using camphor-derived oxazoline N-oxide as dipole.
A Ring Closing Metathesis Approach to the Formal Synthesis of (+)‐Callyspongiolide
作者:Kwang‐Yoon Ko、Zoe E. Wilson、Daniel P. Furkert、Margaret A. Brimble
DOI:10.1002/cctc.202001139
日期:2020.11.19
An enantioselective synthesis of macrocyclic core of (+)‐callyspongiolide is described, constituting a formalsynthesis of this natural product. The synthetic strategy constructs the 14‐membered macrocyclic domain via Yamaguchi esterification followed by a challenging ring‐closingmetathesis (RCM) to effect the final formation of the macrolactone.
作者:Hengbin Wang、Solymar Negretti、Allison R. Knauff、John Montgomery
DOI:10.1021/acs.orglett.5b00381
日期:2015.3.20
A general protocol for the highly exo-selective macrocyclization of ynals using a nickel/N-heterocyclic carbene catalyst system has been developed. A series of 10- to 21-membered macrocycles bearing an exomethylene substituent was synthesized in good yields with excellent regioselectivity (exo/endo >95:5). Very high levels of long-range diastereocontrol can also be achieved for some classes of macrocycles. Complementary to previously reported endo-selective macrocyclizations, this method provides accesses to exoalkylidene macrocycles from simple ynals in high selectivity.