Glycosyl Imidates, 66. Synthesis of the Tetrasaccharide Moiety of Plant Growth Regulator Calonyctin A

3‐ O ‐Benzyl‐protected quinovose 6 was transformed into 1,2‐ O ‐unprotected derivative 9 which on treatment with TBS‐Cl in the presence of a base gave selectively 2‐ O ‐unprotected glycosyl acceptor 10 . Similarly, 3‐ O ‐allyl‐protected quinovose 11 was transformed into 1,2‐ O ‐unprotected derivative 14 . 1,2‐ O ‐Acetylation of 14 , selective removal of the 1‐ O ‐acetyl group with hydrazinium acetate, and subsequent treatment with trichloroacetonitrile in the presence of DBU furnished the versatile 2‐ O ‐acetyl‐3‐ O ‐allyl‐protected quinovosyl donor 17 . Reaction of donor 17 with acceptor 10 in the presence of TMSOTf as the catalyst gave disaccharide 19 . Treatment of 19 with NaOMe/MeOH provided 2b‐ O ‐unprotected derivative 20 which gave with rhamnosyl donor 18 in the presence of TMSOTf as the catalyst trisaccharide 21 . 3b‐ O ‐Deallylation of 21 and subsequent reaction with donor 17 , again in the presence of TMSOTf as the catalyst, gave target tetrasaccharide 2 . Removal of all O ‐protective groups furnished D ‐Quiß(1→3)[ L ‐Rhaα(1→2)] D ‐Quiß(1→2) D ‐Qui ( 3 ), the tetrasaccharide moiety of calonyctin A.