ChemInform Abstract: NOVEL REARRANGEMENT OF DIHYDROMAYURONE WITH BORON TRIFLUORIDE IN ACETIC ACID-ACETIC ANHYDRIDE

1979 ◽  
Vol 10 (17) ◽  
Author(s):  
H. SEKIZAKI ◽  
M. ITO ◽  
S. INOUE
1978 ◽  
Vol 7 (11) ◽  
pp. 1191-1194 ◽  
Author(s):  
Haruo Sekizaki ◽  
Masaaki Ito ◽  
Shoji Inoue

1977 ◽  
Vol 55 (23) ◽  
pp. 3996-4001 ◽  
Author(s):  
Steve Yik-Kai Tam ◽  
Bert Fraser-Reid

Cyclopropyl glycopyranosides which solvolyze via a stabilized cyclopropyl carbinyl-oxocar-bonium ion react under neutral conditions with nucleoside bases in nitromethane at 200 °C to give good yields of the corresponding cyclopropanated nucleosides. Under similar conditions hex-2-enopyranosides (which solvolyze by allyl-oxocarbonium ions) do not react. However, under catalysis by mercuric bromide or acetic acid, the corresponding 2′,3′ unsaturated nucleosides are formed although accompanied by appreciable amounts of 1′,2′-unsaturated-3′-nucleosides. Formation of the latter may be avoided if the hex-2-enopyranosides are first converted to the hex-2-enopyranosyl acetates by treatment with boron trifluoride and acetic anhydride. The derived acetates react with the nucleoside bases without catalysis to give anomeric mixtures of nucleosides, there being no trace of the unwanted 3′-nucleosides.


1991 ◽  
Vol 56 (12) ◽  
pp. 2917-2935 ◽  
Author(s):  
Eva Klinotová ◽  
Václav Křeček ◽  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jaroslav Podlaha ◽  
...  

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.


1988 ◽  
Vol 212 ◽  
pp. 73-79 ◽  
Author(s):  
V. Vajgand ◽  
R. Mihajlović ◽  
Lj. Mihajlović ◽  
V. Joksimović
Keyword(s):  

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