h1

% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Veri:61534,
      author       = {Veri, Elisabetta},
      othercontributors = {Bolm, Carsten},
      title        = {{S}ynthesis and reactivity of alpha-trialkylsilyl
                      alpha-amino acids},
      address      = {Aachen},
      publisher    = {Publikationsserver der RWTH Aachen University},
      reportid     = {RWTH-CONV-123191},
      pages        = {155 S.},
      year         = {2006},
      note         = {Aachen, Techn. Hochsch., Diss., 2006},
      abstract     = {This work deals with the synthesis and reactivity of
                      alpha-trialkylsilyl alpha-amino acids. They were synthesised
                      using an established protocol involving
                      rhodium(II)-catalysed insertion reactions of
                      alpha-trialkylsilyl alpha-diazo esters into N-H bonds of
                      carbamates. As an extension to this procedure, it was
                      accounted that a diastereoselective approach to N-protected
                      alpha-trialkylsilyl alpha-amino acids precursors may lead,
                      after deprotection, to the formation of
                      enantiomerically-pure alpha-trialkylsilyl alpha-amino acids.
                      A variety of diastereoselective synthetic strategies were
                      examinated. These investigations involved the use of
                      alpha-trialkylsilyl alpha-keto-acetates as substrates, as
                      well as various reactants such as chiral amines, ureas, or
                      carbamates as sources of the chiral information. Carbamates
                      were confirmed as the mostly efficient N-H sources for
                      rhodium(II)-catalysed reaction. A diastereoselective N-H
                      insertion reaction was attempted between a
                      alpha-triethylsilyl alpha-diazo benzyl acetate and L-menthyl
                      carbamate. The reaction proceeded in a diastereoselective
                      formation of the N-H inserted product in a diastereomeric
                      ratio of 75 to 25. A part of this project was then devoted
                      to the synthesis of the racemic N-Cbz-protected
                      2-trimethylsilyl glycine. The possibility to obtain the free
                      carboxylic functional group of the named compound from
                      selective deprotection of a corresponding ester moiety was
                      investigated. Various ester protecting groups were
                      considered, the removal of which could give access to the
                      free carboxylic acids and thus to enantiopure alpha-silyl
                      alpha-amino acids through resolution by chemical methods.
                      The most promising result was obtained when the
                      2-triethylsilyl-2-diazo-(4-methoxybenzyl) acetate underwent
                      reaction with aluminum thrichloride/ethanthiol to yield to
                      the mono-deprotected compound in a 1H NMR ratio 1.6 to 1
                      respect to the substrate. Attempts to selective removal of
                      the benzyl ester moiety of N-Cbz-protected alpha-silyl
                      alpha-amino benzyl acetate through selective hydrogenation
                      remained unsuccessful. Hydrogenation over palladium(0)
                      allowed exclusively the formation of the bi-deprotected
                      alpha-silyl alpha-amino acetic acid. The alpha-silyl
                      alpha-amino acid core could become a substructure of a more
                      complicated structure, as for example of a modified Matrix
                      metalloproteinase (MMP) inhibitor. Various synthetic
                      strategies were considered and attempted towards the
                      synthesis of the two building blocks of a silyl modified
                      succinyl hydroxamic acid based MMPs inhibitor. The coupling
                      of a iso-butyl succinyl hydroxamic acid (or the
                      corresponding iso-propyl analogue) and the trifluoroacetic
                      salt of 2-triethylsilyl-2-amino benzyl acetate using various
                      coupling reagents, between them, PyBOP(R) combined with
                      ethyldiisopropylamine, appeared the most promising. Finally,
                      studies on microwave assisted synthesis of N-protected
                      alpha-trialkylsilyl alpha-amino esters were described. A
                      final summary of the several examples reported indicated a
                      shortening of the reaction times under microwave irradiation
                      in comparison to the same transformations performed under
                      standard conditions and conventional heating. To these
                      results, although, did not correspond a sensible enhancement
                      of the chemo- and the stereoselectivity of the discussed
                      reactions.},
      cin          = {150000 / 152310},
      ddc          = {540},
      cid          = {$I:(DE-82)150000_20140620$ / $I:(DE-82)152310_20140620$},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:hbz:82-opus-16924},
      url          = {https://publications.rwth-aachen.de/record/61534},
}