Search

The utility of propargyloxycarbonyl chloride in simultaneous protection of alcohols and amines is explored and the selective deblocking of propargyl carbonates in the presence of propargyl carbamates with benzyltriethylammonium tetrathiomolybdate under mild conditions is achieved. The observation offers a new protecting strategy where an amine and an alcohol group can be protected simultaneously in one pot, and in later synthetic step, is the alcohol group has to be deprotected selectively.

A very simple and efficient stereoselective approach to cis-2,3-disubstituted piperidines via the reduction of N-acyliminium ion intermediates is described. Application of this methodology is exemplified by the enantioselective total synthesis of (+)-(2S,3S)-CP-99,994. [ABSTRACT FROM AUTHOR]

A short, concise synthesis of enantiopure, side chain-modified α-amino adds such as 4-oxo-L-norvaIine, 6-oxo- L-homonorleucine, and 5-cis-alkyl prolines is described. Knoevenagel condensation of L-aminocarboxylate-derived β-ketoesters with aldehydes followed by reductive decarboxylation results in unnatural a-amino acids in good yield. A fluorescent amino acid is synthesized using a similar protocol. These studies show that aminocarbosylate-derived β-ketoesters are very useful intermediates and the method employed is both general and practical for the preparation of γ(δ)-oxo α-amino acids and alkylprolines. [ABSTRACT FROM AUTHOR]

Herein, we report a mild transition metal-free organophotoredox-catalyzed approach for β-hydroxytrifluoromethylation of unactivated alkenes using CF 3 SO 2 Na and acridinium salt. The protocol is compatible with various mono-, di-, and trisubstituted aliphatic unactivated alkenes containing numerous functional groups and natural product derivatives. Further, the postsynthetic modifications of the synthesized trifluoromethylated products have been demonstrated through cross-coupling and functional group interconversion reactions. The method proved to be scalable and it works smoothly under the direct exposure of sunlight. A plausible mechanism has been proposed based on the fluorescence quenching experiment and cyclic voltammetry analysis.

An efficient and straightforward method has been developed for the synthesis of β-benzyl-substituted 5-membered heterocyclic carbaldehydes via transient directing-group-enabled direct γ-C(sp 3 )-H arylation of 3-methylheteroarene-2-carbaldehydes. A wide range of 3-methylheteroarene carbaldehydes undergo coupling with a variety of aryl iodides, including less reactive iodo pyridine derivatives to provide a library of highly selective functionalized products in good to excellent yields. Some of these products have been successfully utilized in synthesizing useful synthetic intermediates.

A unified enantioselective route to total synthesis of diospongins A and B and their enantiomers has been developed employing achiral starting materials. All three stereocenters were introduced by means of catalytic reactions.