ortho esters

https://doi.org/10.1351/goldbook.O04334
Compounds having the structure RC(OR')3 ( R' ≠ H), or the structure C(OR')4 ( R' ≠ H), e.g. HC(OCH3)3 trimethyl orthoformate, C(OCH3)4 tetramethyl orthocarbonate.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1354 (https://doi.org/10.1351/pac199567081307)