nan Kantharaju

Synthesis of Fmoc-amino acid chlorides assisted by ultrasonication, a rapid approach

The chloride derivatives of all common Fmoc-amino acids lacking polar side chains as well as a number of benzyl based side chain protection have been prepared using the corresponding amino acid and thionyl chloride assisted by ultrasound has been described. The protocol is simple, efficient and rapid. All the acid chlorides prepared have been obtained in good yield and purity.

Microwave accelerated efficient synthesis of N-fluorenylmethoxycarbonyl/t-butoxycarbonyl/benzyloxycarbonyl-5-oxazolidinones

The synthesis of N-protected 5-oxazolidinones using amino acids, paraformaldehyde and p-toluene sulfonic acid in a minimum amount of toluene accelerated by microwave irradiation for 3 min in high yield is described.

Efficient Synthesis of O-Succinimidyl-(tert-Butoxycarbonylamino)methyl Carbamates Derived from α-Amino Acids Accelerated by Ultrasound: Application to the Synthesis of Ureidodipeptides

Abstract The synthesis of O-succinimidyl-(tert-butoxycarbonylamino)methyl carbamates employing isocyanates made through the Curtius rearrangement of Boc-amino acid azides in the presence of N-hydroxysuccinimide under the influence of ultrasound is described.

Ab-initio structure determination from X-ray powder data and solid-state DFT study of monohydrate and anhydrous cyclohexanespiro-5′-hydantoin

Abstract The synthesis, thermal analysis, and crystal structures of cyclohexanespiro-5′-hydantoin monohydrate (I) and its anhydrous form (II) have been reported. The compounds (I) and (II) crystallize in space group Pna21 and P21/c, respectively. In the present work, redetermination of crystal structure of (I) and ab-initio structure analysis of (II) have been accomplished from laboratory X-ray powder diffraction data. The crystal structures of both compounds were solved following direct-space approach, and refined by the Rietveld method and solid-state DFT calculation. The results of two refinement procedures for structure determination from X-ray powder data have been compared. The effect of dehydration of (I) has been revealed in different crystal packing arrangements in (I) and (II). In (I), extensive intermolecular N–H · · · O, and O–H · · · O hydrogen bonds involving lattice water molecules generate a two-dimensional C(5)[R33(10)][R43(10)] supramolecular assembly, whereas in (II), a C22(9)[R22(8)] [R22(8)] framework is established via intermolecular N–H · · · O hydrogen bonds.

Curtius Rearrangement Using Ultrasonication: Isolation of Isocyanates of Fmoc-Amino Acids and Their Utility for the Synthesis of Dipeptidyl Ureas

An efficient conversion of Nα-[(9–fluorenylmethyl)oxy]carbonyl (Fmoc) amino acid azides to the corresponding isocyanates using ultrasound is described. The Curtius rearrangement was accomplished using acid azides in toluene solution as well as solid powder at room temperature. All isocyanates synthesized have been obtained as crystalline solids and were characterized. Coupling of isocyanates with amino acid methyl ester hydrochloride salts in presence of N-methylmorpholine (NMM) resulted in Fmoc-protected dipeptidyl urea esters, which have been well characterized by 1H NMR, 13C NMR and mass spectrometry.

tert-Butyl 4,4-dimethyl-5-oxo-1,3-oxazolidine-3-carboxyl­ate

In the title compound, C10H17NO4 the urethane group is planar and the oxazolidinone ring adopts an envelope conformation. Intermolecular C-H·O interactions link the screw- and glide-related molecules into a two-dimensional network parallel to (101).