In our previous study, a cyclic scaffold, 2-hydroxymethyl-3-hydroxytetrahydropyran, was introduced instead of the glycerol moiety to reduce the flexibility of LysoPS and simultaneously to modulate the activity towards GPR34 (Figure ). The carbon atoms of cyclic LysoPS were numbered to correspond to the glycerol framework of LysoPS, from carbon 1, linked to the acyl chain (18:1) to carbon 3, connected to the phosphoserine part (we call this a 1a-2p type analogue: 1a represents the acyl chain at the primary (1°) alcohol and 2p represents the phosphoserine part at the secondary (2°) alcohol (Figure ).