(2S,3R)-(+)-2-hydroxy-3-methylglutaric acid γ-lactone

(4S,5S)-5-(hydroxymethyl)-4-methyldihydrofuran-2(3H)-one

(4R,5S)-dihydro-5-hydroxymethyl-4-methyl-2(3H)-furanone

(2S,3S)-3-Methoxycarbonylmethyl-3-methyl-5-oxo-tetrahydro-furan-2-carboxylic acid

3-(2-Methoxycarbonyl-ethyl)-5-((2S,3S)-3-methoxycarbonylmethyl-3-methyl-5-oxo-tetrahydro-furan-2-carbonyl)-4-methyl-1H-pyrrole-2-carboxylic acid tert-butyl ester