Short asymmetric synthesis of phenanthroindolizidines through chiral homoallylic sulfinamine

An efficient stereocontrolled preparation of chiral phenanthroindolizidines is detailed. The synthesis relies on the stereoselective indium-mediated allylation of 2-(phenanthren-9-yl)acetaldehyde derivatives with chiral tert-butylsulfinamide. Chemoselective transformations from the corresponding homoallylic sulfinamine allow the synthesis of the phenanthroindolizidines in only three synthetic operations, without any detectable racemization. Following this procedure, the synthesis of natural (−)-tylophorine was successfully accomplished.We thank the Spanish Ministerio de Ciencia e Innovación for their financial support (CTQ2011-24165). C. A.-T. thanks the ISO for a grant

A radical addition/cyclization of diverse ethers to 2-isocyanobiaryls under mildly basic aqueous conditions

Mildly basic aqueous conditions facilitated the tert-butyl peroxybenzoate (TBPB) mediated dehydrogenative addition of a range of ethers, including acetals, to diverse substituted 2-isocyanobiaryls. Mechanistic studies suggest that this radical cascade is an example of base promoted homolytic aromatic substitution (BHAS).We thank the Ministerio de Economia y Competitividad (CTQ2015-66624-P) and the University of Alicante (VIGROB-173) for financial support. C. A.-T. thanks the ISO for a grant

Concise asymmetric syntheses of novel phenanthroquinolizidines

The first preparation of enantioenriched phenanthroquinolizidines with a quaternary center at C14a was accomplished in seven steps from readily available starting materials. Key steps were an efficient dynamic kinetic allylation of a diastereomeric mixture of chiral tert-butylsulfinyl ketimines and the construction of a piperidine E ring by rhodium catalyzed hydroformylation. The Stevens rearrangement of the corresponding N-benzyl derivatives took place smoothly, allowing the installation of a benzyl moiety at C9 in a trans relationship with the methyl group. The cytoxicity of the prepared phenanthroquinolizidines was evaluated against different human cancer cell lines.We thank the Spanish Ministerio de Ciencia e Innovación (CTQ2011-24165) and the University of Alicante (VIGROB-173) for financial support. C. A.-T. thanks the ISO for a grant

Syntheses and Cytotoxicity of (R)- and (S)-7-Methoxycryptopleurine

Two efficient protocols are described for the transformation of a key chiral homoallyllic sulfinamine intermediate in four steps into enantioenriched 7-methoxycryptopleurine. While one of the protocols relied on a rhodium catalyzed linear hydroformylation process, the alternative approach was based on a ring-closing metathesis from the corresponding N-allyl-sulfinamine. The cytotoxic evaluation of both enantiomers of the target compound demonstrated that the (R)-compound is much more potent than its antipode against the four cancer cell lines examined.We thank the Spanish Ministerio de Ciencia e Innovación (CTQ2011-24165) for financial support. I.B. acknowledges the Generalitat Valenciana for a postdoctoral fellowship (ACIF/2011/159). C.A.-T. thanks the ISO for a grant

Comatrix Corings and Galois comodules over firm rings

info:eu-repo/semantics/publishe