Process for preparing a cyclic ester or a cyclic amide, comprising the step of: contacting at least one hydroxycarboxylic acid and/or at least one amino-carboxylic acid; or an ester, or salt thereof; wherein said hydroxycarboxylic acid is a 2-hydroxycarboxylic acid; and wherein said amino carboxylic acid is a 2-amino-carboxylic acid; with at least one acidic zeolite comprising: - two or three interconnected and non-parallel channel systems, wherein at least one of said channel systems comprises 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 24 as measured by NMR; or - three interconnected and non-parallel channel systems, wherein at least two of said channel systems comprise 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 8 as measured by NMR; wherein each X is Al or B, and wherein the process is performed at a pressure between 0.5 and 20 bar; and wherein said cyclic ester or cyclic amide is a compound of formula: wherein Z 1 is O or NH; Z 2 is O or NH; R 1 and R 2 are each independently hydrogen or a group selected from C 1-6 alkyl; C 2-6 alkenyl; C 6-10 aryl; C 1-10 alkylC 6-10 arylene; C 6-10 arylC 1-6 alkylene; or C 2-6 alkynyl; each group being optionally substituted by one or more substituents selected from C 1-6 alkyl, C 1-6 alkyloxy. contacting at least one hydroxycarboxylic acid and/or at least one amino-carboxylic acid; or an ester, or salt thereof; wherein said hydroxycarboxylic acid is a 2-hydroxycarboxylic acid; and wherein said amino carboxylic acid is a 2-amino-carboxylic acid; with at least one acidic zeolite comprising: - two or three interconnected and non-parallel channel systems, wherein at least one of said channel systems comprises 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 24 as measured by NMR; or - three interconnected and non-parallel channel systems, wherein at least two of said channel systems comprise 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 8 as measured by NMR; - two or three interconnected and non-parallel channel systems, wherein at least one of said channel systems comprises 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 24 as measured by NMR; or - three interconnected and non-parallel channel systems, wherein at least two of said channel systems comprise 10-or more-membered ring channels; and a framework Si/X 2 ratio of at least 8 as measured by NMR; wherein each X is Al or B, and wherein the process is performed at a pressure between 0.5 and 20 bar; and wherein said cyclic ester or cyclic amide is a compound of formula: wherein Z 1 is O or NH; Z 2 is O or NH; R 1 and R 2 are each independently hydrogen or a group selected from C 1-6 alkyl; C 2-6 alkenyl; C 6-10 aryl; C 1-10 alkylC 6-10 arylene; C 6-10 arylC 1-6 alkylene; or C 2-6 alkynyl; each group being optionally substituted by one or more substituents selected from C 1-6 alkyl, C 1-6 alkyloxy. Z 1 is O or NH; Z 2 is O or NH; R 1 and R 2 are each independently hydrogen or a group selected from C 1-6 alkyl; C 2-6 alkenyl; C 6-10 aryl; C 1-10 alkylC 6-10 arylene; C 6-10 arylC 1-6 alkylene; or C 2-6 alkynyl; each group being optionally substituted by one or more substituents selected from C 1-6 alkyl, C 1-6 alkyloxy.