Open KlementineJBS opened 3 months ago
Using purified KBS49 from #184
TLC today was unclear. Using more polar solvent revealed an extra spot, identity unknown. Ninhydrin staining suggests that spot stuck to origin + spot with Rf of ~ 0.5 are both amines.
SM appears to be completely consumed.
Evidence of desired product at 559.30+ [M+H]+ and singly-deprotected product at 744.27+ [M+H]+. Many other peaks are present too - unsure what these represent. No sign of SM.
Unknown peaks: 352.24+, 426.93+, 548.13+, 573.78+, 597.25+ and 275.09-, 627.75-, 833.27-.
Interestingly, despite having left reaction capped and turned off overnight, a new spot seems to have emerged. (Compare bottom right TLC, taken 11 am this morning, with top right TLCs, taken yesterday afternoon.) This could be due to a more concentrated spot.
Worked up as with #159 :
vial: 15.7587 mass: 46.9 mg
Crude NMR difficult to decipher. Oddly, the 4.76 methylene peak is very small as compared with others - maybe due to mixture containing thiosalicylic acid byproduct, which contributes lots of aromatic peaks?
Will try columning with rightmost conditions (2% of MeOH with ammonia mixture in DCM).
Somewhat difficult to TLC as fractions were highly dilute. Solvent system used is a 20% mixture of a premade 10% ammonia-saturated methanol in DCM.
Fractions | vial (g) | mass (mg) | substance |
---|---|---|---|
23-27 | 15.9250 | 3.2 | seems to be SM |
33-39 | 15.7585 | 6.5 | seems to be singly denosylated product |
40-53 | 16.1060 | 31.5 | deprotected bis product (!) |
NMR is definitely unclear for first two samples, but much better for bis sample. It seems that deprotection results in a shift of the noticeable methylene peak (believed to be between triazole and amine) from 4.76 (protected) to 4.07 (deprotected). Other methylene peaks are shifted also (3.41 -> 2.76).
The nosyl peaks (8 x aromatic peaks) have also disappeared, and triazole H appears to be well distinguished from naphthalene peaks.
1H NMR (300 MHz, Chloroform-d) δ 8.07 – 7.90 (m, 4H), 7.86 (s, 2H), 7.68 – 7.45 (m, 10H), 4.10 – 4.05 (m, 4H), 2.76 (t, J = 7.2 Hz, 4H), 1.75 (s, 4H), 1.35 (s, 8H).
nmr300_20240318_KBS44-4 F33-39_1.zip nmr300_20240318_KBS44-1 F23-27_1.zip nmr300_20240318_KBS44-2 F40-52_10.zip
Peaks at 559.32+ [M+H]+ and 571.31+ [M+Na]+ confirm presence of product. Unsure about peak at 625.26+.
F2: Product, no clear sign of possible side products. Unidentified peaks at 698+, 726+ and lots of negative ions. F3: Product, same as above. Unidentified peaks at 703+, negative. F4: Some product, similar amounts of SM (fully alkylated and protected).
KBS prep fractions 09-08-24 F4.pdf KBS prep fractions 09-08-24 F3.pdf KBS prep fractions 09-08-24 F2.pdf
Link to HIRAC and master page #186
KBS44 Nosyl deprotection of linear amines.docx
Reaction scheme
Outcome
31.5 mg of completely deprotected product (0.0564 mmol, 52%)