Complete facial selectivity in the Diels-Alder reaction of a 5-amino-5-carboxycyclopentadiene derivative

5-tert-Butoxycarbonylamino-5-carbethoxy-2-tert-butyldimethylsilyloxy-cyclopentadiene undergoes a Diels-Alder reaction exclusively from the face syn to the nitrogen functionality. Complete reversal of facial bias may be achieved, but at the cost of diminished reactivity, through steric shielding of the N-syn face.     

Structure of 2-amino-5-methylthiazoline and its N-methyl derivatives

As indicated by PMR spectroscopic data, 2-amino-5-methylthiazoline and 2-methylamino-5-methylthiazoline exist in the imine form in the temperature interval from +20° to –100° C. Interaction of the 2-amino-5-methylthiazoline with methyl iodide results in alkylation at the endocyclic nitrogen atom.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 415–419, March, 1993.     

Structure of 2-amino-4-thiazolinone

It was shown by the methods of IR and NMR spectroscopy that 2-amino-4-thiazolinone (pseudothiohydantoin) exists in an amino form in the crystalline state and in solutions in dimethyl sulfoxide, water, and trifluoroacetic acid, and in this amino form all the nitrogen-carbon bonds are partially double. In dimethyl sulfoxide and trifluoroacetic acid there is an autoassociation with the formation of dimers. Inhibited rotation of the amino group around the exocyclic nitrogen-carbon bond was detected. The results of a calculation of the IR spectrum of 2-amino-4-thiazolinone according to the force-field method agrees with the experimental data.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1066–1070, August, 1984.     

The rearrangement of 2-amino-5-benzoyloxazoles with dimethylamine

The rearrangement of 2-amino-5-phenacyloxazoles with dimethylamine is described. One such rearrangement provided an unexpected tricyclic product.     

Variable strategy toward carbasugars and relatives. 6. Diastereoselective synthesis of 2-deoxy-2-amino-5a-carba-beta-L-mannopyranuronic acid and 2-deoxy-2-amino-5a-carba-beta-L-mannopyranose

Efficient, total syntheses of novel 2-deoxy-2-amino-5a-carba-beta-L-mannopyranuronic acid (1) and 2-deoxy-2-amino-5a-carba-beta-L-mannopyranose (2), a positional stereoisomer of validamine, have been achieved in 28% and 24% overall yields and in 12 steps and 13 steps, respectively, from 2-[(tert-butyldimethylsilyl)oxy]furan (3) and (2S)-2,3-O-isopropylideneglyceraldehyde N-benzyl imine (4) via two highly diastereoselective Mukaiyama aldol-related chemical maneuvers. The strategy, which furnishes the targeted carbasugars in enantiopure forms, allows for complete control of the configuration at all five contiguous stereocenters of the targets by utilizing the sole element of chirality present in the aldimine progenitor 4.     

Ratiometric fluorescence detection of pyrimidine/purine transversion by using a 2-amino-1,8-naphthyridine derivative.

A new class of abasic site-binding fluorescence ligands, Naph-NBD in which 7-nitrobenzo-2-oxa-1,3-diazole (NBD) is connected to 2-amino-7-methyl-1,8-naphthyridine (Naph) by a propylene linker, is presented for the ratiometric assay for SNPs typing. In solutions buffered to pH 7.0 (I = 0.11 M, at 5 degrees C), Naph-NBD is found to selectively recognize pyrimidine bases over purine bases opposite the abasic site in DNA duplexes (K11/M(-1): T, 8.1 x 10(6); C, 2.5 x 10(6): G, 0.33 x 10(6); A, 0.27 x 10(6)). The binding of Naph-NBD is accompanied by significant quenching of the fluorescence from the naphthyridine moiety (lambda max, 409 nm), while the emission from the NBD (lamda max, 544 nm) is relatively unaffected. Such a fluorescence response of Naph-NBD allows the emission ratio detection of pyrimidine/purine transversion.     

Reactivity of 2-amino-1,3,4-thiadiazoles. Methylation reactions of some 2-amino-5-benzoyl-1,3,4-thiadiazoles

Methylation reactions of 2-amino-5-benzoyl-1,3,4-thiadiazoles 1a-d are reported as a function of alkylating agents (methyl iodide, dimethyl sulfate-potassium carbonate, diazomethane, dimethyl-sulfate-sodium methoxide). Methylation occurs at both the ring nitrogen in position 3 and the exocyclic nitrogen atom.