Synthesis of alkyl 2-(bromomethyl)aziridine-2-carboxylates and alkyl 3-bromoazetidine-3-carboxylates as amino acid building blocks

Spiro-C(sp3)-atom transfer: Creating rigid three-dimensional structures with Ph2SCN2

The introduction of a single C-atom into organic substrates typically results in the formation of flat molecules containing unsaturated C(sp)-centers. Adding a single C(sp3)-atom surrounded by four σ-C-C bonds, which opens up the three-dimensional space, is an unresolved problem in synthetic chemistry. We report the synthesis and application of the diazosulfur ylide Ph2S=C=N2 reagent that combines the reactivity of both sulfur ylides and diazo compounds to create carbon spiro-centers in a general fashion by the sequential or single-step installation of a C(sp3)-atom. New C-C and C-X (where X is O or N) bonds can be created around the C(sp3)-atom, which can ultimately be extended to four C-C σ-bonds in one step without resorting to transition metal catalysis. Ph2SCN2 can also be used to access highly strained frameworks containing (oxa)spiro[2.2]pentanes as well as tricyclic spiro-compounds.

Methyl 2-Amino-4-[1-(tert-butoxycarbonyl)azetidin-3-yl]-1,3-selenazole-5-carboxylate

Methyl 2-amino-4-[1-(tert-butoxycarbonyl)azetidin-3-yl]-1,3-selenazole-5-carboxylate as a newly functionalized heterocyclic amino acid was obtained via [3+2] cycloaddition. The structure of the novel 1,3-selenazole was unequivocally confirmed by detailed 1H, 13C, 15N, and 77Se NMR spectroscopic experiments, HRMS and elemental analysis.

Facile synthesis of novel amino acid-like building blocks by N-alkylation of heterocyclic carboxylates with N-Boc-3-iodoazetidine

An efficient protocol providing easy access to highly functionalized heterocyclic compounds as novel organic building blocks was developed by coupling alkyl pyrazole-, indazole- and indolecarboxylates with N-Boc-3-iodoazetidine. The synthesized compounds are representatives of constrained non-chiral synthetic azole carboxylates in their N-Boc protected ester forms. Diversification of the prepared heterocyclic building blocks was achieved via application of palladium-catalyzed Suzuki-Miyaura cross-coupling reactions. In total, 34 building blocks were obtained to form a highly diversified small molecule collection. The structure of the novel heterocyclic compounds was investigated and verified by advanced NMR spectroscopy methods.

Synthesis of stereodefined piperidines from aziridines and their transformation into conformationally constrained amino acids, amino alcohols and 2,7-diazabicyclo[3.3.1]nonanes

2-(2-Cyano-2-phenylethyl)aziridines were converted into novel cis- and trans-2-chloromethyl-4-phenylpiperidine-4-carbonitriles via alkylation with 1-bromo-2-chloroethane followed by microwave-assisted 6-exo-tet cyclization and regiospecific ring opening. The latter piperidines were used as eligible substrates for the synthesis of stereodefined 2-chloromethyl-, 2-hydroxymethyl-, and 2-carboxymethyl-4-phenylpiperidine-4-carboxylic acids, 2-hydroxymethyl-4-phenylpiperidine-4-carbonitriles, 3-hydroxy-5-phenylazepane-5-carbonitriles, and 5-phenyl-2,7-diazabicyclo[3.3.1]nonanes.