4,6‐Diphenylthieno [3,4‐d][1,3]dioxol‐2‐one 5,5‐Dioxide, A Novel Activating Agent for Peptide Syntheses

Abstract

acetylation to yield the flavin analogs ( 4 ) , ( 5 ) , or (6), respectively, in good yields; they can be converted into the ribityl derivatives by deacetylation. 5-Deazaribofauin ( 4 ) , R2= R'A solution of 6-[N-(tetraacetyl-~-ribityl)-3,4-~ylidino]uracil (31, R1=RZ, (2.50g, 4.7mmol) in DMF (8ml) is treated with pocl, (0.80 ml, 8.7 mmol). The mixture is allowed to stand for 30min at room temperature and for 15min at 100°C. It is then poured onto ice, adjusted to pH = 6 with ammonia at O"C, and stirred for 30min. The product is filtered off, and washed with a large volume of water. After drying over P 2 0 5 , 2.30g (91 %) of ( 4 ) is obtained. Deacetylation in 50 % saturated methanolic ammonia solution yields 1.1Og (62 %) ( 4 ) , RZ = R', which is thin-layer chromatographically and spectrally identical with authentic 5-Deaza-5-thia-1 H-riboflavin (5), R2= R'A solution of ( 3 ) , R' =R2, (3.7mmol) in CHC13 (5ml) is treated with SCl, (0.50 ml, 7.8 mmol) and stirred for 12h at room temperature. The solvent is then removed in vacuo and the residue taken up in lOml DMF. This solution is added dropwise and slowly to 100ml of a 0.1 M solution of Na2SzO4 in 0.1 M phosphate buffer (pH = 7). After complete decoloration the solution is extracted three times with 100ml CHCl3 and the CHCl, removed in vacuo. The residual oil crystallizes upon addition ofdiethyl ether;yield 1.30g (62 %) (5). Deacetylation in 20ml saturated methanolic ammonia solution affords 0.64g (44 %) ( 5 ) , R2=R'. 'H-NMR (1 N K2C03 in DzO): 6=2.05 (s, 7,8-CH3, 6H), 3.52-4.28 (m, 10-ribityl, 7H) and 6.50-6.75 ppm (6,9-CH, 2H); UV: pH=13, anion, h,,, (E)= 262 (27 720), 298 sh (8320), 3 16 nm sh (3 170); pH = 2, neutral entity, A , , , (~)=252 (18610), 280 sh (9590), and 345 nm sh (1980); pK=5.310.1. [Z 459 IE] German version: Angew. Chem. 88,475 (1976)

Synthesis of peptidyl fluoromethyl ketones and peptidyl .alpha.-keto esters as inhibitors of porcine pancreatic elastase, human neutrophil elastase, and rat and human neutrophil cathepsin G

“…Note that for 21 the corresponding -keto acid was much less potent. Cbz-Ala-Ala-Ala-Ala-C02Et (30)15 was quite potent in spite of the lack of proline at P2.…”

Self-Immolative Nitrogen Mustard Prodrugs for Suicide Gene Therapy

“…The aqueous stability of the compounds (pH 7.4; 37 °C) varied considerably. The least stable prodrugs (23,25) showed little difference between the bischloro (23) and bisfluoro (25) congeners, implying that their instability lies elsewhere in the molecule. By contrast, and as expected, the bisfluoro compounds 42 and 44 were much more stable than their bischloro counterparts 37 and 40.…”

“…15 The cytotoxicity of the compounds was assayed by a modification of the published procedure. 29 Cells (2 × 10 6 ) were seeded into 6-well plates, producing confluent monolayers in 48 h. Compounds were dissolved in DMSO at 10 mM (30) or 100 mM (25,42,44) immediately prior to treatment, diluted in full medium, and added to the wells. A similar concentration of drug solution was added after an incubation of 1 h, and the cells were incubated for an additional 20 h. The cells were harvested and reseeded in quadruplicate in 96-well plates at ∼2 × 10 3 cells/well and incubated until the control wells achieved confluence.…”

“…Aliquots (10 µL) were injected onto a Partisphere 5-µm C18 column (110 mm × 4.6 mm) and eluted isocratically (1 mL/min) with 10 mM ammonium acetate (pH 5.0) containing percentages of methanol chosen to produce a retention time of 3-4 min and monitored at the optimum wavelength (12, 10%, 246 nm; 20, 10%, 213 nm; 23, 63%, 255 nm; 25, 50%, 250 nm; 30, 65%, 258 nm; 32, 37, 58%, 268 nm; 40, 58%, 253 nm; 42, 45%, 267 nm; 44, 43%, 251 nm). The amount of starting material remaining after various periods of incubation at 37 °C was determined either by repeat injections (7.5-min intervals) from a single vial (12,20,30,32,37,40,42,44) or by delayed injections (1-min intervals) from a new vial each time (23,25). Kinetic Determinations.…”

“…The aniline-derived self-immolative nitrogen mustards 37 , 40 , 42 , and 44 were obtained by a different route. In a first attempt the linker 8a was activated by treatment with 4,6-diphenylthieno[3,4- d ][1,3]dioxol-2-one 5,5-dioxide , to give the corresponding carbonate 33 . This intermediate is stable only at low temperature (−78 °C) and could not be isolated.…”