Mercury(II) chloride in the synthesis of nido-carborane derivatives with B-N,B-O,and B-S bonds

Russian Chemical Bulletin - The use of mercury(II) chloride for the synthesis of nido-carborane derivatives with B-O, B-N, and B-S bonds was considered. The involvement of HgCl2 allows one to...     

Amination of 2-hydroxy- and 2,3-dihydroxynaphthazarins. Synthesis of echinamines A and B,metabolites produced by the sand dollar <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

2-Hydroxynaphthazarins reacted with aqueous ammonia at the C¹=O carbonyl group, following the addition-elimination pattern with formation of 8-aminojuglone derivatives. Reactions of 2,3-dihydroxynaphthazarins with the same reagent involved the C²=O carbonyl group of the corresponding 1,2-naphthoquinoid tautomer to produce 2-aminonaphthazarin derivatives. 7-Ethyl-2,3,6-trihydroxynaphthazarin (echinochrome) reacted with aqueous ammonia to give 3(2)-amino-7-ethyl-2(3),6-dihydroxynaphthazarins (echinamines A and B) that are metabolites recently isolated from the sand dollar Scaphechinus mirabilis.     

Wellposedness of a linearized problem of supersonic flow past a wedge in the case of arbitrary perturbations

The method of dissipative energy integrals is used in studying the wellposedness of the mixed problem on the flow past a wedge in the linear formulation.     

Glycosylation of betulin and its acetates in the presence of cadmium carbonate

The glycosylation of betulin and its acetates by -acetobromoglucose in toluene in the presence of cadmium carbonate is considered. It has been shown that the reaction is accompanied by Wagner-Meerwein rearrangements of the initial alcohols in rings A and E. This leads to the formation — in addition to acetates of betulin glycosides — of derivatives of allobetulin — A-nor-³⁽⁵⁾-allobetulin and A-nor-³⁽⁵⁾-betulin — as was shown by¹H and¹³C NMR spectroscopy.Pacific Ocean Institute of Biochemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 182–187, March–April, 1984.     

Chemistry of naphthazarin derivatives. 8. Determination of structures of substituted 2-hydroxy-6(7)-methoxynaphthazarins and 7(8)-hydroxypyranonaphthazarins by IR spectroscopy

A set of substituted 2-hydroxy-6(7)-methoxynaphthazarins and 7(8)-hydroxypyranonaphthazarins were synthesized. The IR spectra of 2-hydroxy-6-methoxynaphthazarins and 7-hydroxypyranonaphthazarins, on the one hand, and of 2-hydroxy-7-methoxynaphthazarins and 8-hydroxypyranonaphthazarins, on the other hand, have the characteristic nonoverlapping intervals of stretching vibration frequencies of the -hydroxy groups. These regularities confirm the structures of cristazarin and 6-methylcristazarin, which are metabolites of lichen Cladonia cristatella.