(Z)-tert-Butyl 2-(4-amino-9H-fluoren-9-ylidene)acetate

Abstract

The title compound, C19H19NO2, obtained as an almost equimolar mixture (as shown by 1H NMR) with the E isomer through a Wittig reaction between 4-amino-9H-fluoren-9-one and the stabilized ylide Ph3P=CHCO2C(CH3)3, was obtained pure in the Z configuration following crystallization from toluene. The mol­ecule shows a planar arrangement of the ring system and the new double bond, whereas the carbonyl O atom forms a 45.1 (3)° dihedral angle with it. The mol­ecules are linked by N—H⋯O hydrogen bonds, forming cyclic structures with R 4 4(24) graph-set motifs. These motifs are connected to each other, giving rise to a sheet structure parallel to the ab plane. The linkage within the sheets is further enhanced by π–π stacking inter­actions between the fluorene units [centroid–centroid distance = 3.583 (2) Å].

Syntheses and evaluation of the antioxidant activity of acitretin analogs with amide bond(s) in the polyene spacer

“…It is worth mentioning that compound 27 was obtained as a mixture of isomers (ratio E/Z ¼ 55:45 by 1 H NMR). Crystallization of said mixture from PhMe, gave in low yield the Z isomer (Z À 27), as identified by single crystal X-ray crystallography [8]. Similarly, Wittig reaction of Ph 3 P]CHCO 2 tBu with 3-acetyl-1-tosylpyrrole (28), readily synthesized from pyrrole [9], provided the anticipated adduct as a mixture of geometric isomers (ratio E/Z ¼ 65:35, as shown by 1 H NMR).…”

“…Drying over Na 2 SO 4 and evaporation to dryness left a residue, from which pure amides 19a-c were obtained through FCC. 8 Hz, H-7), 7.37 (1H, td, J 7.2 and 1. 6 Hz, H-6), 6.56 (1H, dd, J 8.0 and 2.…”

“…Perusal of the IC 50 's or % inhibition values (Table 1) shows that the most potent inhibitor, namely compound 5 (IC 50 35 mM), is found within the subset of the anilide type compounds (1-7), followed by compound 12 (IC 50 45.2 mM) belonging to the other subset of compounds (8)(9)(10)(11)(12)(13)(14)(15), namely of the cinnamic acid-type. In these two subsets of compounds, two other potent inhibitors may be also identified, namely compounds 6 (IC 50 52.4 mM) and 8 (IC 50 65 mM) respectively.…”

“…The involvement of these particular heterocyclic rings in the design of our analogs stemmed from the anticipation that they could be readily incorporated into the spacer by using the commercially available indole-3-carboxylic acid and -carboxaldehyde or the readily synthesized 3-acetylpyrrole, which include the hydrolytically stable N-C]C-CO structural motif. The latter, would allow for the replacement of either three or two conjugated double bonds of the spacer by the isosteric structural units NH-CO-C(R)]CH-N(R)-CO (analogs 1-7) and CO-N(R)-CH]C(R) (analogs [8][9][10][11]13), respectively. Finally, the implication of tert-butyl esters in the present study was thought of interest because we had observed, from biological studies of other types of a,b-unsaturated acids, that their corresponding tert-butyl esters were more potent inhibitors of lipoxygenase (LOX) than the free acids [6].…”