Geometric differences explanation and their relevance:
Despite SARMs having wildly different structures regarding their shape, the relevant binding interactions are still present because most SARMs preserve the correct 3D pharmacophore, as they possess the spatial arrangement of hydrophobic regions and hydrogen bonding groups needed to interact with the androgen receptors ligand binding pocket, this meaning that they will possess structures that are compatible with the AR shape despite replacing some of the functional groups and geometry present in AAS molecules but will still possess a similar and compatible geometric structure, they replace some AAS structures and functional groups with other structures and functional groups like aromatic rings like benzene, bicyclic systems, nitriles, trifluoromethyl groups, ether linkages, or heterocycles, that in theory recreates the same spatial geometry and electronic interactions needed for the bonding to occur in the AR receptor. In addition, SARMs often induce a slightly divergent conformational change and behave differently in the receptor, affecting co activator recruitment differently across tissues, and they are generally resistant to metabolism by 5α-reductase and aromatase conversion. In theory these modifications regarding their geometric structure should keep the relevant parts of the interactions for muscle growth and get rid of the rest that are causing the androgenic side effects.
Simplification: The geometric shape tweaks present on SARMs should get rid of the unwished interactions and androgenic sides of AAS preserving the key elements needed for muscle growth and still fitting the required structural criteria to bind to the AR. However, this selectivity is relative, failing the original premise of the creation of SARMs, as in practice SARMs can still produce some androgenic effects, more frequently at higher doses, this point in particular will be relevant when I disclose the rest of the cons of SARMs.
Testosterone skeletal form:
View attachment 50102
Ostarine (enobosarm, MK-2866, GTx-024):
View attachment 50103