Stereoselectiveethynylation of functionalized β-C-glycosyl aldehydes has been achieved with various organometallic alkynes. The diastereoselectivity is highly dependent on the organometallic alkyne and on the functionalization on the C-6 position of the glycoside. The stereoselective reaction conducted with ester-functionalized aldehyde, followed by Mitsunobu reaction and two Pd-catalyzed regio- stereo-