Synthesis of (2RS,E)-3-Ethylidene-azetidine-2-carboxylic acid (rac. polyoximic acid)
摘要:
Treatment of alpha-diazo beta-ketoester 4 with a catalytic amount of rhodium (II) acetate followed by Wittig reaction with phosphorane 5 gave the isomeric phenylthioester derivative 6a and 6b. Reduction of 6a led to the corresponding allylic alcohol 7, which was further converted into the bromide 8. Dehalogenation of 8 with NaBH4/DMF resulted in compound 9, which was deprotected with trifluoroacetic acid, giving racemic polyoximic acid (1).
Desymmetrizing reductive aldol cyclizations of enethioate derivatives of 1,3-diones catalyzed by a chiral copper hydride
作者:Jun Ou、Wing-Tak Wong、Pauline Chiu
DOI:10.1039/c2ob25206f
日期:——
A range of enethioate derivatives of 1,3-diones underwent reductive aldol cyclizations catalyzed by a chiral copper hydride generated in situ from 5 mol% TaniaPhos (SL-T001-1), 5 mol% Cu(OAc)2·H2O, 5 mol% bipyridine and 2.0 equiv. of PhSiH3, to furnish polycyclic β-hydroxythioester products bearing three newly established contiguous stereocenters, with >98 : 2 dr and in up to 94% yield and 98% ee.
The organocatalytic enantio- and diastereoselective cycloetherification of 1,3-cyclohexanedione-bearing enones involving the in situ generation of chiral cyanohydrins was developed. This transformation offers the first catalytic asymmetric approach to oxadecalin derivatives containing contiguous tetrasubstituted chiral carbons at the bridge heads of the fused ring systems. Depending on substituents
Reductive aldol cyclizations of unsaturated thioester derivatives of 1,3-cyclopentanedione catalyzed by chiral copper hydrides
作者:Jun Ou、Wing-Tak Wong、Pauline Chiu
DOI:10.1016/j.tet.2011.07.057
日期:2012.4
and enantioselectivity (up to 90% ee). With the related indanedione enethioate derivatives, the reductive aldol cyclization could attain up to 96% ee. These results demonstrate that enethioates have a significantly different reactivity and selectivity profile compared to enoate derivatives in the copper-catalyzed reductive aldol cyclization.
Diversity‐oriented biosynthesis of a library of antimycin‐like compounds (380 altogether) was accomplished by using multiplex combinatorial biosynthesis. The core strategy depends on the use of combinatorial chemistry at different biosynthetic stages. This approach is applicable for the diversification of polyketides, nonribosomal peptides, and the hybrids that share a similar biosynthetic logic.
Nickel-catalyzed, highly diastereoselective annulations between activated allenes and 2-acetylarylboronic acid or 2-formylarylboronic acids are reported. No ligand for nickel is required, and the reactions proceed efficiently at room temperature to give a broad range of substituted 3-methyleneindan-1-ols. Preliminary results of an enantioselective variant are also described.