Proton sponge → Monomethyl auristatin E intermediate-9

HRID 2282801

Reaction equation

HRID 2282801 reaction equation
[CH2:1]([O:8][C:9]([N:11]([CH3:27])[C@@H:12]([C@@H:23]([CH3:26])[CH2:24][CH3:25])[C@H:13]([OH:22])[CH2:14][C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH3:28]N(C1C2C(N(C)C)=CC=CC=2C=CC=1)C.F[B-](F)(F)F.C[O+](C)C>ClCCCl>[CH2:1]([O:8][C:9]([N:11]([CH3:27])[C@@H:12]([C@@H:23]([CH3:26])[CH2:24][CH3:25])[C@H:13]([O:22][CH3:28])[CH2:14][C:15]([O:17][C:18]([CH3:20])([CH3:21])[CH3:19])=[O:16])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1

Participants

5

Reactant 3

HCID 88675Proton spongeHCID 2735153Oxonium, trimethyl-, tetrafluoroborate(1-) (1:1)HCID 10022629tert-butyl (3R,4S,5S)-4-{[(benzyloxy)carbonyl](methyl)amino}-3-hydroxy-5-methylheptanoate

Product 1

HCID 10249994Monomethyl auristatin E intermediate-9

Reagents, catalysts & solvents 1

HCID 111,2-DichloroethaneSolvent

Procedure

To a solution of #3 (8.4 g, 22 mmol, 1 eq.) in 1,2-dichloroethane (25 mL, 0.88 M) were added molecular sieves (4 Å, 0.7 g) and Proton sponge (1,8-bis(dimethylamino)naphthalene) (13.4 g, 59.2 mmol, 2.7 eq.), followed by trimethyloxonium tetrafluoroborate (9.10 g, 61.6 mmol, 2.8 eq.). After stirring overnight, the reaction mixture was filtered through Celite. The filtrate was concentrated in vacuo and the residue was purified by silica gel chromatography (Gradient: 0% to 40% 1:1 acetone:ethyl acetate in heptane) to give #@2 (8.7 g, 68%) as a colorless oil. 1H NMR (400 MHz, DMSO-d6), presumed to be a mixture of rotamers: δ 7.28-7.40 (m, 5H), 5.01-5.13 (m, 2H), 3.89-4.08 (br m, 1H), 3.70-3.82 (m, 1H), 3.18 and 3.26 (2 s, total 3H), 2.66 and 2.71 (2 br s, total 3H), 2.44-2.53 (m, 1H, assumed; partially obscured by solvent peak), 2.17-2.24 (m, 1H), 1.71-1.86 (br m, 1H), 1.39 and 1.39 (2 s, total 9H), 1.31-1.40 (m, 1H), 0.94-1.08 (m, 1H), 0.76-0.91 (m, 6H).

Workup

  1. filtrationthe reaction mixture was filtered through Celite
  2. concentrationThe filtrate was concentrated in vacuo
  3. customthe residue was purified by silica gel chromatography (Gradient: 0% to 40% 1:1 acetone:ethyl acetate in heptane)
  4. customto give #@2 (8.7 g, 68%) as a colorless oil
  5. additiona mixture of rotamers
  6. customδ 7.28-7.40 (m, 5H), 5.01-5.13 (m, 2H), 3.89-4.08 (br m, 1H), 3.70-3.82 (m, 1H), 3.18 and 3.26 (2 s, total 3H), 2.66 and 2.71 (2 br s, total 3H), 2.44-2.53
  7. custom2.17-2.24 (m, 1H), 1.71-1.86 (br m, 1H), 1.39 and 1.39 (2 s, total 9H), 1.31-1.40 (m, 1H), 0.94-1.08 (m, 1H), 0.76-0.91 (m, 6H)

Sources & evidence

ORD record
ord-ee0c18f2ac6b434bb088645cad01a63d
Source dataset
uspto-grants-2015_09
Patent number
US09138486B2

Linked notes

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