Herein, we report the structure-activity relationship of a chiral morpholine-based scaffold, which led to the identification of a potent and selective dopamine 4 (D4) receptor antagonist. The 4-chlorobenzyl moiety was identified, and the compound was designated an MLPCN probe molecule, ML398. ML398 is potent against the D4 receptor with IC50 = 130 nM and K i = 36 nM and shows no activity against the other dopamine receptors tested (>20 μM against D1, D2S, D2L, D3, and D5). Further in vivo studies showed that ML398 reversed cocaine-induced hyperlocomotion at 10 mg/kg.

Herein, we describe the enantioselective construction of the 12-membered macrocyclic pyrrole core 4 of marineosin A in 5.1% overall yield from (S)-propylene oxide. The route features a key Stetter reaction to install a 1,4-diketone, which is then subjected to Paal-Knorr pyrrole synthesis and ring closing metathesis (RCM) to afford macrocycle 4. A divergence point in the synthetic scheme also enabled access to a highly functionalized spiroaminal model system 8 via an acid-mediated hydroxyketoamide cyclization strategy.

In this Letter, we describe a short, 6-step enantioselective route to spiroaminal lactam model systems reminiscent of marineosins A and B has been developed starting from either (R)- or (S)-hydroxysuccinic acid, respectively, in ~9% overall yield. This route enables late stage incorporation of the pyrrole ring at C5 via nucleophilic displacement of an iminium triflate salt.