Solid-liquid phase transfer catalytic synthesis of α- amino acid via alkylation and nucleophilic addition of benzaldehyde imines

Development of Potent Inhibitors of Botulinum Neurotoxin Type B

“…The β -Amino Thiols. Among the various β-amino thiols used in this work, only three of them, compounds 4 , 8 , and 9 , have not been previously described. − They were prepared following reported methods from their corresponding noncommercially available α-amino acids. The t-Boc-amino esters 1 and 5 were prepared using a solid−liquid-phase transfer catalytic method with the (benzylideneamino)acetic acid ethyl ester and either the 4-(chloromethyl)-( tert -butyl)benzamide, or the 4-(bromomethyl)-phenyl( tert -butyl)sulfonamide (prepared from the commercially available 4-(chloromethyl)benzoyl chloride and 4-(chlorosulfonyl)benzoic acid, respectively), followed by acidic hydrolysis of the benzylidene moiety and protection of the free amine by a Boc group (data not shown).…”

Phase-Transfer Catalysis Reaction with Strong Bases

“…In most cases, only monoalkylation was obtained (59-89% yield depending on the alkyl halide used) followed by hydrolysis of the alkylated imine to yield the corresponding amino acid. range of the diactivated imines (14.5-24.3, mostly 17-21, for a wide variety of ketimines and aldimines activated by benzylic, ester, and/or nitrile groups [36,40]), the reactions may be hydroxide transfer rate limited and, therefore, accessible quaternary ammonium cations (and tetrabutylammonium as always) were good choices for these reactions (see Chapter 6, Section G). Yields improved to 76-95% when the methylene group was activated by the imine and a nitrile group [39].…”

“…This reaction has been expanded to include the synthesis of a-amino acids with two different alkyl groups, by using a monoalkylated aldimine as the starting material (see Figure 8-10) [40]. Since the monoalkylated aldimine is less acidic and more sterically hindered than the ketimines O'Donnell used, a stronger base and less hydration are needed to enhance the reaction.…”

One‐Pot Synthesis of 6‐Aminopyrido[2,3‐d]pyrimidin‐7‐ones

“…In particular, the use of alkenes in such reactions ensured practical methods for the synthesis of pyrrolidines , . Besides, several examples of [3+2] cycloaddition reactions that lead to imidazole, 1,2,4‐triazole and oxazoline derivatives were described in the literature , . In addition, there were several methods for the synthesis of several six‐membered heterocycles, starting from N ‐arylidene glycinates, unsaturated aldehydes and ketones …”