Three bromotyrosine derivatives, one terminating in an unprecedented diketocyclopentenylidene enamine

Absolute Configuration and Conformational Study of Psammaplysins A and B from the Balinese Marine Sponge Aplysinella strongylata

“…11 The relative configuration of psammaplysin A (1) was first determined as (6S*,7S*) in 1985 by single-crystal X-ray crystallographic analysis of its diacetyl derivative (2). 3 Subsequent reports on the relative configuration of psammaplysins C−H were made by comparing their specific rotation values with those of psammaplysin A, 4,8,9,11,12 by chemical shift comparisons, [5][6][7]11 or by ROESY/NOESY correlation data. 8−10 The potent biological activities of the psammaplysins, together with their unusual 1,6-dioxa-2-azaspiro [4.6]undeca-2,7,9-triene motif, clearly justify efforts to resolve their absolute configuration, an aspect of their structure elucidation that could not be pursued in the original X-ray crystallographic work due to inferior crystal quality.…”

“…Psammaplysin B (4) (ref 11): [α] D 22 = −56 (c 0.3, MeOH); lit. [α] D 22 = −60 (c 0.63, MeOH); 3 UV (MeOH) λ max (log ε) 258sh (3.96), 230sh (4.35), 206 (4.90); ECD (MeOH, λ [nm] (Δε), c = 5.89 × 10 −4 M): 277 (−0.73), 242 (7.02), 234sh (6.16), 207 (−22.41).Acetylation, Hydrolysis, and MPA Ester Formation of Psammaplysin A. N-Acetylpsammaplysin A(5). A sample of psammaplysin A (34.4 mg) in pyridine (0.5 mL) was cooled in an ice bath.…”

Synthesis and Antimicrobial Evaluation of New Pyrrolo-isoxazolidine Derivatives

“…The reactions of nitrones with alkene occur via the involvement of 4π and 2π-electrons system which suggested their occurrence under the thermal modes [5]. Pyrrolo-isoxazolidine derivatives exhibit a wide diversity of biological activities like antibacterial [21], antifungal [22], anti-inflammatory [23], anticancer [24], anticonvulsant [25], antitubercular [26], anti-influenza [27], anti-HIV [28] and antistress [29]. Some of these heterocycles are also reported as broad spectrum antibiotics due to their actions against the Gram-positive bacteria [30].…”

One-pot synthesis of new series 3,4,5-trisubstituted–dihydroisoxazoline derivatives via 1,3-dipolar cycloaddition of nitrile oxides with chalcones

“…Among them five-membered heterocycles, isoxazolines are of considerable interest due to their versatile application in pharmaceutical and agrochemical agents. Isoxazoline derivatives have been reported to possess antidiabetic, 1 antiinfluenza virus, 2 antifungal, 3 glycoprotein IIb/IIIa receptor antagonists, 4 antiHIV, 5 spermicidal and antiHIV, 6 analgesic and antiinflammatory, 7 and β-adrenergic receptor antagonist, 8 antitumour, 9 antistress 10 and anticancer properties. 11 Isoxazolines also act as an important building block for the synthesis of biologically active molecules.…”