Syntheses and 1H- and 13C-nuclear magnetic resonance spectra of all positional isomers of methyl mono-O-tetradecanoyl-.ALPHA.- and .BETA.-D-glucopyranosides.

Studies of intramolecular rearrangements of acyl-linked glucuronides using salicyclic acid, flufenamic acid, and (S)- and (R)-benoxaprofrn and confirmation of isomerization in acyl-linked .DELTA.9-11-carboxytetrahydrocannabinol glucuronide

“…The first is the downfield shift of the signal for the proton at the position of the new ester linkage. This has considerable precedent in the carbohydrate literature (40)(41)(42)(43)(44)(45)(46). This shift is observed not only when position 2, 3, or 4 is substituted.…”

“…The anomeric C-l proton signal is shifted downfield in the 1-O-acyl conjugate, relative to when that position is free (as, for example, in free glucuronic acid). The second trend is the upfield shift of the C-l proton signal as the position of acylation is further removed (40)(41)(42)(43). In nonglucuronide carbohydrate systems (45,46), this upfield shift is also present, but the magnitude of the shift varies and the order of anomeric proton signals does not always correspond to the order of the position of acylation (40)(41)(42)(43).…”

Mode of Action on Deacetylation of Acetylated Methyl Glycoside by Cellulose Acetate Esterase fromNeisseria siccaSB

“…For acetylated saccharides, deacetylation of acetylated hydroxyl groups at positions C-2, C-3, C-4, and C-6 results in a downfield shift (1-3 ppm) of the peak(s) corresponding to the neighboring carbon(s). 20) When the chemical shifts of product A were compared with those of 2,3,4,6-AcMeGlc, chemical shifts at positions C-2 and C-4 for product A were downfield shifts of about 3 ppm each, and the values at the others positions were almost equal. This result suggests that product A was a deacetylated compound of 2,3,4,6-Ac-MeGlc at position C-3, namely 2,4,6-Ac-MeGlc.…”

Total synthesis of astrosterioside A, an anti-inflammatory asterosaponin

“…The shift of C1' signal to a high field (by 3.6 ppm) was in agreement with the acylation at it neighboring 2'-OH. 30 At this stage, the protecting groups in hexasaccharide 22 were synchronized with acyl groups. Thus, the four benzyl groups were hydrogenolysed over Pd(OH) 2 /C and the resultant hydroxyl groups were protected with benzoyl groups, providing hexasaccharide 23 (94% over two steps).…”

“…The shift of the C1 0 signal to a high field (by 3.6 ppm) was in agreement with the acylation at its neighboring 2 0 -OH. 30,31 The remaining less reactive 2 0 -OH in 18 was then glycosylated with perbenzoyl D-quinovopyranosyl imidate 10 28 under stronger reaction conditions (0.2 equiv. of TMSOTf, 4 Å MS, CH 2 Cl 2 , 0 1C-rt), leading to the desired tetrasaccharide 5 in a high 91% yield (Scheme 4).…”