4-Pentenyl (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-(3,6-di-O-acetyl-2-deoxy-2-phthalimido-beta-d-glucopyranosyl)-(1-->3)-(2,6-di-O-benzoyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-beta-d-glucopyranoside (4) was synthesized by regioselective glycosylation of 4-pentenyl (2,6,-di-O-benzoyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-beta-d-glucopyranoside and (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-3,6-di-O-acetyl-2-deoxy-2-phthalimido-beta-d-glucopyranosyl chloride. By conversion of the protecting groups followed by thioacetylation, 4 was transformed into the corresponding lacto-N-neotetraose derivative, 5-(acetylthio)pentenyl (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-O-(3,6-di-O-acetyl-2-acetamido-2-deoxy-beta-d-glucopyranosyl)-(1-->3)-(2,4,6-di-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-acetyl-beta-d-glucopyranoside (6). The lacto-N-neotetraose derivative 6 was introduced into carbosilane dendrimer cores of three shapes, and three kinds of new carbosilane dendrimers peripherally functionalized by lacto-N-neotetraose were obtained.