1,721,343 research outputs found
Fate of C-24 hydrogen atoms of cholesterol during its conversion into tigogenin in Digitalis lanata
No full text(24R)-[24-3H]- and (24S)-[24-3H]-cholesterols are transformed into tigogenin [(25R)-5α-spirostan-3β-ol] in Digitalis lanata without involvement of the hydrogen atoms at C-24; this confirms that the reduction of the Δ24-precursor of cholesterol is a ‘trans’ process
Origin of the 27-methylene group of the steroidal sapogenin convallamarogenin
No full textIn convallamarogenin biosynthesized in Convallaria majalis the 27-methylene group is derived from C-2 of mevalonic acid
Stereochemistry of the hydrogen introduction at C-25 in the biosynthesis of tomatidine
No full textThe C-26 atom of tomatidine, bearing the nitrogen atom, derives from the C-2 atom of MVA; from this it is inferred that the introduction of hydrogen at the C-25 atom of the Δ24 biosynthetic intermediate occurs from the 24-si, 25-si face
Cis and trans β,γ-disubstituted δ-valerolactones: conformational studies and configurational assignments by molecular mechanics
No full textTwo β,γ-disubstituted δ-valerolactones 2 and 3 were synthesized starting from (R)-(+)-limonene. The most significant conformations for each lactone were determined by molecular mechanics calculations; then the 1H-NMR coupling constants for each pair of vicinal hydrogen atoms of the lactone rings were calculated through suitable Karplus equations. Comparison of experimental and calculated coupling constants allowed the assignment of the vicinal stereorelationship between the β and the γ substituents in 2 and 3
Stereochemistry of reduction of the 24,25-double bond in the biosynthesis of tigogenin in digitalis lanata
No full textIn tigogenin [(25R)-5α-spirostan-3β-ol] biosynthesized in Digitalis lanata a 4-pro-R-proton of mevalonic acid occupies the 24-pro-S-position, which indicates that reduction of Δ24-biosynthetic intermediates occurs with trans-stereochemistry
Conversion of β-sitosterol into both fucosterol and isofucosterol in Tenebrio molitor
No full textIt has been demonstrated with cold trap experiments that Tenebrio molitor transforms β-sitosterol not only into fucosterol, but also into isofucosterol
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