Synthesis of (R)-3,4-dihydro-2H-pyran-2-carboxaldehyde: application to the synthesis of potent adenosine A(2A) and A(3) receptor agonist

Synthesis of potent adenosine A(2A) and A(3) receptor agonist from the modification of adenosine-5'-N-ethylcarboxamide (NECA) has been reported. Diastereoisomer possessing an (R) 3,4-dihydro-2H-pyranyl (DHP) moiety exhibited the highest affinity at the A(2A) and A(3) receptors. The key steps involve the synthesis of (R)-3,4-dihydro-2H-pyran-2-carboxaldehyde (7), which was obtained through the enzyme catalyzed kinetic resolution of (±)-2-acetoxymethyl-3,4-dihydro-2H-pyran (5).