Either the alpha or gamma rings of these compounds may mimic the A ring of estradiol and compete for the estrogen receptor.
The fragment ion at m/z 134.88 [M + H]+, which contained the phenolic A-ring of a compound with a triple bond, has already been reported as a distinctive mass fragment of resveratrol [ 26].
"Dead" and "deathly" repeat "deadly" from the previous stanza, so that we're caught in a ring of steel, compounded further by the "three ranckes of yron teeth" in stanza XIII.
The HMBC correlations of H-15/C-9, C-10, C-11 suggesthatthat a methyl group (C-15) linked at C-10, forming an 11-membered carbocyclic ring of compound 1.
A structural feature especially common among isoprenoid compounds is a ring of six carbon atoms; the simplest compound possessing this structure is cyclohexane (not an isoprenoid), represented by structural formula 1, by a condensed version 2, or simply by the hexagon 3.
Analogs designed to explore the effect of ring size on activity (compounds 37 and 38) demonstrated a preference for the six-membered ring of compound 10, and polar analogs such as compound 11 displayed poorer activity.
Opening of furan ring of compound 5 was a crucial step, which was carried out with PTSA in Ac2O at low temperature to produce diacetyl 6 in an 88% yield.
Molecular docking investigations showed that the trimethoyphenyl ring of compound 5k occupied a position near the cofactor-binding site in the rhDHFR-inhibitor complex, with close intermolecular contacts with Asp21, Phe31, Ser59, Ile60 and Pro61.
The A and B rings of balanol bind in the adenine and ribose subsites, respectively, whereas the aromatic C ring binds to the polyphosphate subsite in a manner highly reminiscent of the phenyl ring of compound 18.
These observations indicated that the smaller molecular weight was due to the substituent group localized on the thiazine ring of compound 4, which is 12 amu less than a vinyl group.
