KBS44-2 - Nosyl deprotection of KBS49

[KlementineJBS]

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%)

[KlementineJBS]

12.03.24

Using purified KBS49 from #184

1. Dissolved KBS49 (101.2 mg, 0.109 mmol) in dry DMF (3 mL)
2. Added thiosalicyclic acid (69.2 mg, 0.449 mmol, 4.1 equiv.) and K2CO3 (120.2 mg, 0.870 mmol, 8 equiv.)
3. heated to 60 C and left stirring from 5.30 pm

[KlementineJBS]

13.03.24

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.

[KlementineJBS]

LRMS of reaction mixture

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-.

KBS44-2_RM.pdf
KBS44-2 RM.d.zip

[KlementineJBS]

14.03.24

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 :

• added 25 mL ether
• washed with LiCl solution (sat., 3 x 20 mL)
• washed with Na2CO3 solution (sat., 2 x 20 mL)
• washed with brine (25 mL)
• dried and rotovapped

vial: 15.7587
mass: 46.9 mg

[KlementineJBS]

H NMR

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?

nmr300_20240314_KBS44-2 cr_1.zip
KBS44-2 cr.pdf

[KlementineJBS]

Column conditions

Will try columning with rightmost conditions (2% of MeOH with ammonia mixture in DCM).

[KlementineJBS]

Column details

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 (!)

[KlementineJBS]

H NMR

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).

KBS44-2 fractions.pdf

nmr300_20240318_KBS44-4 F33-39_1.zip
nmr300_20240318_KBS44-1 F23-27_1.zip
nmr300_20240318_KBS44-2 F40-52_10.zip

[KlementineJBS]

LRMS

Peaks at 559.32+ [M+H]+ and 571.31+ [M+Na]+ confirm presence of product. Unsure about peak at 625.26+.

KBS44-2 F40-53.pdf
KBS44-2 F40-53.d.zip

[KlementineJBS]

HPLC (LRMS)

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

KBS prep fractions 09-08-24 F2.d.zip

[KlementineJBS]

[KlementineJBS]

IR

KBS44-2 25-06-24.pdf
KBS44-2.zip