“…Meanwhile, the chemical synthesis of I has emerged as a further option, having been synthesised by the catalytic oxidation of cyclopentene (Orita et al, 1986;Choudary et al, 1991;Antonelli et al, 1998;Griffith et al, 2000;Wang & Dai, 2002;Griffith & Kwong, 2003;Chen et al, 2006aChen et al, , 2006bChe et al, 2006;Shoair & Mahamed, 2006;Saedi et al, 2012aSaedi et al, , 2012b, 1,5-pentanediol (Iwahama et al, 2000;Chen et al, 2007;Balaraman et al, 2013), 1,3-cyclohexanedione (Yuan & Zhao, 2010;Tachikawa et al, 2013), dihydropyran (English & Dayan, 1957), tetrahydropyran (Smith & Scarborough, 1980), 2-cyclohexenone (Travis et al, 2002), cyclopentane-1,2- (Gao et al, 2009), or glutaraldehyde (Chu et al, 2012), by the acidic hydrolysis of glutaronitrile (Marvel & Tuley, 1925), by γ-butyrolactone (Paris et al, 1957) or by electrosynthesis (Lyalin & Petrosyan, 2009). However, all these methods entailed the use of expensive substrates or catalysts, harsh conditions or toxic reagents.…”