Formation of trioxadamantane type aglucones of 3-methoxy secologanin derivatives
Acidic transformation of some 3,4-dihydro-3-substituted secologanin derivatives produced trioxadamantane type compounds. The formation of the bridged tricyclic products from monocyclic educts is interpreted as multistep hydrolysis and transacetalation accompanied by deglucosylation.
Krajsovszky, Gabor,Kocsis, Akos,Szabo, Laszlo Ferenc,Podanyi, Benjamin
New cyanoglycosides, hydracyanosides D, E, and F, from the leaves of Hydrangea macrophylla
Three new cyanoglycosides named hydracyanosides D (1), E (2), and F (3) were isolated from the leaves of Hydrangea macrophylla cultivated in China together with 17 known constituents including hydracyanoside A (4). Their structures were elucidated on the basis of chemical and physicochemical evidence.
SELECTIVE TRANSFORMATIONS OF SECOLOGANIN: DIHYDROXYLATION
Sweroside tetraacetate ( 2b ) has been converted in high yield by osmylation to the epimeric glycols 3 and 4 ( R=H ) which have been separated.This reaction proceeds with high chemoselectivity for reaction at the vinyl side chain but with low stereoselectivity, leading to a small excess of the 3-R isomer.Secologanin derivatives appear to show a much lower chemoselectivity in this reaction, but the stereoselectivity is considerably higher, and opposite to that in the sweroside example.Conditions have been found for oxidizing the dimethylacetal 5b of secologanin tetraacetate in useful yields to the epimeric glycols 6 and 7 ( R=H ); in this reaction a large excess of the 3-S isomer is formed.The reasons for these differences in selectivity appear to be related to differences between the two series in conformational preference.
Purdy, John Richard,Hamilton, Raymond G.,Akhter, Lalarukh,McLean, Stewart
p. 210 - 214
(2007/10/02)
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