Stable Isotopically-Enriched D-Glucose: Strategies to Introduce Carbon, Hydrogen and Oxygen Isotopes at Various Sites

[13C,15N]2-Acetamido-2-deoxy-d-aldohexoses and Their Methyl Glycosides: Synthesis and NMR Investigations of J-Couplings Involving 1H, 13C, and 15N

“…For 3, 3 J H1,H2 could not be used reliably because the coupling is small in both anomers. In this case, the assignment was made by measuring 3 J C5,H1 in [5][6][7][8][9][10][11][12][13] C]3; the observed coupling (1.2 Hz) confirmed the -configuration (a coupling >5 Hz is expected in the R-anomer). 25a The favored pyranosyl ring conformations of 2-5 orient the C1-N1 bond equatorial in aqueous solution at pD 10.5.…”

“…In this case, however, only configuration at C1 is relevant. 2 J C1,C5 values in the R-pyranoses (6,7,9,11, 13) range from -1.8 to -2.1 Hz and are negative in sign. 41 Little or no coupling is observed in -pyranoses.…”

An NMR investigation of putative interresidue H-bonding in methyl α-cellobioside in solution

“…Methyl a-cellobioside 4 (Scheme 1), whose solution conformation has been studied previously, 24,25 was chosen as the target disaccharide, selectively labeled with 13 C at C4 0 (4 0 ) (Scheme 1), because (a) synthesis of D-[4-13 C]glucose 26 and assembly of the labeled disaccharide are straightforward, and (b) the equatorial C4 0 -O4 0 bond in 4/4 0 is expected to enhance the 3h J C4 0 ,O3H value, if it exists, due to the terminal oxygen in-plane effect on 3 J CH values. 6,27 In addition, in 4/4 0 , the C4 0 -C5 0 -O5 0 -O3H pseudo-torsion angle approaches 180°, rendering this system ideally suited for detection of a trans-H-bond 3 J CCOH if conventional Karplus behavior applies.…”

13C-Labeled D-Ribose: Chemi-Enzymic Synthesis of Various Isotopomers

“…After the reaction is complete ( < 15 min), the pH is lowered to 4.2 with acetic acid to stabilize the nitriles (the latter readily hydrolyze under alkaline conditions to yield aldonamides and aldonates (16,17)), and the labeled nitriles are reduced with Pd/BaSO 4 ( 5%) and H 2 at pH 4.2 (for C 5 aldononitriles) or pH 1.6 (C 2 -C 4 aldononitriles ). Optimal hydrogen pressures vary from 1 atm to 60 psi depending on the structure of the nitriles (11)(12)(13). Reduction probablyproceeds via acyclic aldimines (these m~ cyclize to glycosylamines), which hydrolyze at pH 1.6-4.2 to give C-2 epimeric (1_1 C]aldoses III having one more carbon than the parent aldose (Scheme 1 ).…”

“…The introduction of 13 (11)(12)(13), which represents a truncated form of the classical Kiliani-Fischer chain extension reaction of the aldoses (14,15). A parent aldose I is condensed in aqueous solution with K 13 CN at pH 7.3, generating a mixture of(l-13 C]cyanohydrins (aldononitriles) II.…”