I agree.It would be interesting to see if they stand out in the progression from methyl to propyl.
Also, just gonna be forthright with my bias here: I think in silico work is great for hypothesis generation, but it needs validation in actual biological systems.
Classic Psychedelic Reference Compounds at 5-HT₂A
| Compound | Amine–ASP155 (Å) | TRP Score | 4-Sub Contacts | Key Contacts |
| DOM | 2.86 | 0.246 | ASN343 (3.40 Å), LEU229 (3.40 Å) | TYR370 |
| DET | 4.90 | 0.135 | N/A | SER159, PHE340 |
| DMT | 4.59 | 0.178 | N/A | SER159, PHE339/PHE340 |
| DOET | 4.27 | 0.293 | SER242 (3.67 Å), PHE340 (3.77 Å) | ILE152 (2.70 Å) |
| 2C-D | 6.48 | 0.316 | LEU229, SER239, ASN343 | SER242-amine, PHE339/PHE340 |
| 2C-E | 6.45 | 0.304 | ASN343 (3.52 Å), PHE339 (3.99 Å) | SER242-amine, PHE339/PHE340 |
| α-Ethyl-DOM | 3.43 | 0.284 | SER239 (3.41 Å), ASN343 (3.62 Å), LEU229 (3.68 Å) | TRP151 (3.80 Å) |
1. DOM is the structural reference standard
DOM maintains the tightest amine–ASP155 salt bridge (2.86 Å). The 4-methyl group packs cleanly against LEU229 and ASN343 without displacing the amine. The anchor is prioritized, and the TRP score remains moderate (0.246).
2. 2C-D and 2C-E lose the salt bridge entirely
Both compounds have the amine displaced > 6 Å from ASP155. This is a major structural shift:
- The amine instead H-bonds to SER242.
- ASP155 contacts the 2-methoxy group instead of the amine.
- 2C-E has a tighter ASP155–methoxy contact (3.32 Å) than 2C-D (3.46 Å) , suggesting the ethyl group pushes the ring further into the pocket and pulls the methoxy closer to ASP155.
- Both gain higher TRP scores (0.316 and 0.304) as the ring drops deeper into the orthosteric pocket.
- The 4-ethyl in 2C-E reaches further into the lipophilic pocket than the 4-methyl in 2C-D, touching PHE339 CZ at 3.99 Å.
DOET maintains a moderate amine anchor (4.27 Å) while achieving a strong TRP score (0.293) and the best lid contact of the set (ILE152, 2.70 Å). The 4-ethyl contacts SER242 and PHE340.
4. α-Ethyl-DOM is the most balanced modulator candidate
α-Ethyl-DOM maintains a good amine anchor (3.43 Å) while achieving a strong TRP score (0.284). The α-ethyl reaches toward TRP151 (3.80 Å), distributing contacts across the deep pocket, the anchor, and the lid simultaneously.
5. DMT and DET maintain moderate anchors but low lid engagement
DMT and DET keep moderate amine anchors (4.59/4.90 Å) but have the lowest TRP scores (0.178/0.135). The tryptamine scaffold does not stack effectively with the pocket tryptophans.
Metrics:
Amine–ASP155 (Å): Distance between the ligand amine nitrogen and the closest ASP155 carboxylate oxygen. Lower = tighter salt bridge. < 3 Å = strong ionic H-bond; 3–5 Å = moderate; > 5 Å = amine displaced.
TRP Score: π-stacking between the ligand aromatic ring and all pocket tryptophans (TRP141, TRP151, TRP336, TRP367). Higher = more π-stacking.
4-Substituent Contacts: Receptor residues within 4 Å of the 4-position substituent carbons. Shows where the 4-sub packs—deep pocket, backbone, or lid.
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