Concise Syntheses of Arabinogalactans with β‐(1→6)‐Linked Galactopyranosyl Backbone and α‐(1→3)‐Linked Arabinofuranosyl Side Chains

Abstract

Abstract4‐Methoxyphenyl glycoside of β‐D‐Galp‐(1→6)‐[α‐L‐Araf‐(1→3)‐] β‐D‐Galp‐(1→6)‐β‐D‐Galp‐(1→6)‐{β‐D‐Galp‐(1→6)‐[α‐L‐Araf‐(1→3)‐]β‐D‐Galp‐(1→6)‐β‐D‐Galp‐(1→6)‐}2β‐D‐Galp‐(1→6)‐[α‐L‐Araf‐(1→3)‐]β‐D‐Galp‐(1→6)‐β‐D‐Galp was synthesized with 2, 3, 4, 6‐tetra‐O‐benzoyl‐α‐D‐galactopyranosyl trichloroacetimidate (1), 6‐O‐acetyl‐2, 3, 4‐tri‐O‐benzoyl‐α‐D‐galactopyranosyl trichloroacetimidate (11), 4‐methoxyphenyl 3‐O‐allyl‐2, 4‐di‐O‐benzoyl‐β‐D‐galactopyranoside (2), isopropyl 3‐O‐allyl‐2, 4‐di‐O‐benzoyl‐1‐thio‐β‐D‐galactopyranoside (12), 4‐methoxyphenyl 2, 3, 4‐tri‐O‐benzoyl‐β‐D‐galactopyranoside (5), and 2, 3, 5‐tri‐O‐benzoyl‐α‐L‐arabinofuranosyl trichloroacetimidate (8) as the key synthons.

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone

“…Rhamnose contains several hydroxy groups with similar chemical activities, so regioselective protection and alkylation are challenges. Common protecting groups of the hydroxy group at 1-position of rhamnose include allyl [28], methoxyphenyl [29] and 1-thiorhamnoside [30]. Compared with the reaction conditions of the other two protecting groups, the conditions of selective allyl protection are mild, and no irritant gas is produced during the reaction, so selective allyl protection was chosen to afford 1 .…”

Synthesis of plant arabinogalactans

“…There are some reports dealing with the synthesis of arabinogalactans which have been contributed mainly from three research groups led by van Boom [13], Lipták [14][15][16][17], and Kong [18][19][20][21][22][23][24][25][26]. They have developed quite different methods, i.e., the 1,2-anhydrogalactose-based method [13], the (methoxydimethyl)methyl (MIP) and (2-naphthyl)methyl (NAP) protection technique [14][15][16][17], and the selective acylation or glycosylation strategy [18][19][20][21][22][23][24][25][26].…”

“…They have developed quite different methods, i.e., the 1,2-anhydrogalactose-based method [13], the (methoxydimethyl)methyl (MIP) and (2-naphthyl)methyl (NAP) protection technique [14][15][16][17], and the selective acylation or glycosylation strategy [18][19][20][21][22][23][24][25][26]. In the synthesized tetramers, the reducing end of the downstream galactose unit is functionalized with a dodecanoate spacer to enable conjugation to a solid support via a peptide linkage.…”