Ivan

Nature, Published online: 11 August 2022; doi:10.1038/d41586-022-02178-w

Nature Chemistry, Published online: 21 July 2022; doi:10.1038/s41557-022-01007-x

Nature, Published online: 29 June 2022; doi:10.1038/s41586-022-04846-3

Diastereoselective phosphonylation of the chiral cyclic imines were obtained from L-pyroglutamic acid in the presence of TiCl₄. A complex between the imine, carbonyl group of the ester, and titanium was took place. Then, selective trans attack by (EtO)₃P moiety from the opposite less hindered face (re) would account for the diastereoselectivity. The first synthesis of (2S,5R)-5-methyl-5-(phosphono)-proline was reported herein.

Abstract

We report here the first diastereoselective synthesis of (2S,5R)-5-methyl-5-(phosphono)-proline, a phosphoproline derivative from L-pyroglutamic acid. The main feature of this methodology is the transformation of L-pyroglutamic acid into chiral cyclic imines as a versatile intermediate followed by diastereoselective nucleophilic addition of trialkyl phosphites or diethyl phosphite in the presence of PhB(OH)₂, Ph₂P(O)OH, (PhO)₂P(O)OH, Ph(H)P(O)OH and TiCl₄. N-Cbz Cleavage with simultaneous hydrolysis of phosphonate and carboxylate esters in the quaternary cyclic α-aminophosphonate, gave the target compound.

Abstract

An enantioselective chiral phosphoric acid catalyzed formal [4+2] cycloaddition between 2-benzothiazolimines and N-H-1,3-dienecarbamates is described. A divergence in reaction pathways was observed depending on the dienes employed. The reaction performed with 4-substituted dienes produced benzothiazolopyrimidines as major product in yields ranging from 42 to 67%, as single diastereoisomer and with enantioselectivity between 93 and 99%. The same reaction performed with 3-substituted dienes, however, gave highly enantioenriched 1,2,3,4-tetrahydroquinolines as the major products albeit with moderate diastereoselectivity.

Publication date: 3 December 2021

Source: Tetrahedron, Volume 102

Author(s): Alexandra E. Golliher, Antonio J. Tenorio, Brandon M. Cornali, Erika Y. Monroy, Rodolfo Tello-Aburto, F. Omar Holguin, William A. Maio

Abstract

A coordination and copolymerization strategy was adopted to synthesize bonded Eu(III) polymer phosphor poly(MMA‐co‐Eu(BTZ)₂(Phen)(UA)) (PM‐Eu for short) with methyl methacrylate (MMA) as polymer matrix and Eu‐complex monomer Eu (BTZ)₂(Phen)(UA) using azodiisobutyronitrile as initiator. The copolymer PM‐Eu exhibits thermal stability up to 266°C. It also exhibits wide and strong excitation bands from 230 to 380 nm monitored at 612 nm, matching well with the 365 nm of ultraviolet (UV) chip. PM‐Eu displays Eu(III) characteristic peaks at 579, 591, 612, 650, and 700 nm under the excitation of 365 nm of UV light. Meanwhile, it has a fluorescence lifetime of 0.582 ms, and it has a higher quantum yield of 0.672. All the results prove that the polymer PM‐Eu can be applied as a red component for fabrication of near UV‐based white light‐emitting diode (LED).