Direct synthesis of poly(p-phenyleneethynylene)s from calcium carbide

An efficient method for the preparation of poly(p-phenyleneethynylene)s (PPEs) from direct coupling reactions between aryl diiodides and inexpensive chemical feedstock calcium carbide is developed.

Quercitylcinnamates, a new series of antidiabetic bioconjugates possessing α-glucosidase inhibition and antioxidant

Antidiabetic agents possessing dual functions, α-glucosidase inhibition and antioxidant, have been accepted to be more useful than currently used antidiabetic drugs because they not only suppress hyperglycemia but also prevent risk of complications. Herein, we design antidiabetic bioconjugates comprising of (+)-proto-quercitol as a glucomimic and cinnamic analogs as antioxidant moieties. Fifteen quercitylcinnamates were synthesized by direct coupling through ester bond in the presence of DCC and DMAP. Particular quercityl esters 6a, 7a and 8a selectively inhibited rat intestinal maltase and sucrose 4-6 times more potently than their parents 6, 7 and 8. Of synthesized bioconjugates, 6a was the most potent inhibitor against maltase and sucrose with IC₅₀ values of 5.31 and 43.65 μM, respectively. Of interest, its inhibitory potency toward maltase was 6 times greater than its parent, caffeic acid (6), while its radical scavenging (SC₅₀ 0.11 mM) was comparable to that of commercial antioxidant BHA. Subsequent investigation on mechanism underlying inhibitory effect of 6a indicated that it blocked maltase and sucrose functions by mixed inhibition through competitive and noncompetitive manners.

Control over the color transition behavior of polydiacetylene vesicles using different alcohols

In this contribution, we investigate the color transition behavior of polydiacetylene (PDA) vesicles upon exposure to different chemical stimuli. A series of linear and branched alcohols are used as model additives, allowing systematic control of their molecular shape and polarity. The PDA vesicles are fabricated by using three monomers, 10,12-pentacosadiynoic acid (PCDA), 10,12-tricosadyinoic acid (TCDA), and N-(2-amino ethyl)pentacosa-10,12-dyinamide (AEPCDA). When a series of linear alcohols is used, the longer alcohol length causes color transition of all PDA vesicles. In this system, the penetration of linear alcohols into the inner layer of PDA vesicles is dictated by their polarity. The change of -OH position within the alcohol molecule also affects the degree of penetration. It requires a higher amount of the 2-propanol to induce color transitions of the PDAs compared to that of the 1-propanol. The addition of methyl branches into the hydrophobic tail of alcohols causes an increase in steric effect, which hinders the penetration as well. When the 2,2-dimethyl-1-propanol is used as a stimulus, the color transition of PDAs occurs at much higher alcohol concentration compared to 2-methyl-1-butanol, 3-methyl-1-butanol, and 1-pentanol. The variation of PDA structures also affects their ability to interact with the alcohols. The modified head group of poly(AEPCDA) promotes the ability to distinguish between 1-propanol and 2-propanol or 1-propanol and ethanol.

Pathogenic mechanism of mutations in the thyroid hormone receptor β gene

BACKGROUND

Resistance to thyroid hormone (RTH) is characterized by a variable degree of reduced tissue sensitivity to thyroid hormone (TH). It is usually caused by mutations in the TH receptor-β (TRβ) gene.

AIMS

To characterize clinical and molecular features of a Thai patient with RTH. Functional significance of the identified mutation as well as other uncharacterized TRβ mutations was also investigated.

MATERIALS AND METHODS

Exons 3-10 of the TRβ gene were assessed by PCR-sequencing. Functional characterization of the mutant TRβ was determined by the luciferase reporter system.

RESULTS

A mutation in exon 9 of the TRβ gene resulting in a methionine to threonine substitution at codon 313 was identified. The functional consequence of this mutation and other uncharacterized known mutations (p.I276L, p.I280S, p.L330S, p.G344A, p.M442T) was evaluated by transfection studies. Four out of 6 had a significant impairment of T3-dependent transactivation. When co-transfected with the wild-type TRβ, all exhibited a dominant negative effect.

CONCLUSION

A de novo mutation was identified in the patient with clinical diagnosis of RTH. Our findings provide a strong support that interfering with the T3-mediated transcriptional activation of the wild-type TRβ independent of the ability to activate transcription is a major pathogenic mechanism causing RTH.

In vitro inhibitory effects of cyandin-3-rutinoside on pancreatic α-amylase and its combined effect with acarbose

The inhibitory activity on pancreatic α-amylase by cyanidin-3-rutinoside was examined in vitro. The IC₅₀ value of cyanidin-3-rutinoside against pancreatic α-amylase was 24.4 ± 0.1 μM. The kinetic analysis revealed that pancreatic α-amylase was inhibited by cyanidin-3-rutinoside in a non-competitive manner. The additive inhibition of a combination of cyanidin-3-rutinoside with acarbose against pancreatic α-amylase was also found. These results provide the first evidence for the effect of cyanidin-3-rutinoside in a retarded absorption of carbohydrates by inhibition of pancreatic α-amylase which may be useful as a potential inhibitor for prevention and treatment of diabetes mellitus.

Synthesis, characterization and biological evaluation of succinate prodrugs of curcuminoids for colon cancer treatment

A novel series of succinyl derivatives of three curcuminoids were synthesized as potential prodrugs. Symmetrical (curcumin and bisdesmethoxycurcumin) and unsymmetrical (desmethoxycurcumin) curcuminoids were prepared through aldol condensation of 2,4-pentanedione with different benzaldehydes. Esterification of these compounds with a methyl or ethyl ester of succinyl chloride gave the corresponding succinate prodrugs in excellent yields. Anticolon cancer activity of the compounds was evaluated using Caco-2 cells. The succinate prodrugs had IC₅₀ values in the 1.8–9.6 μM range, compared to IC₅₀ values of 3.3–4.9 μM for the parent compounds. Curcumin diethyl disuccinate exhibited the highest potency and was chosen for stability studies. Hydrolysis of this compound in phosphate buffer at pH 7.4 and in human plasma followed pseudo first-order kinetics. In phosphate buffer, the k_obs and t_1/2 for hydrolysis indicated that the compound was much more stable than curcumin. In human plasma, this compound was able to release curcumin, therefore our results suggest that succinate prodrugs of curcuminoids are stable in phosphate buffer, release the parent curcumin derivatives readily in human plasma, and show anti-colon cancer activity.

Oxidative palladium catalysis in S(N)Ar reactions leading to heteroaryl ethers from pyridotriazol-1-yloxy heterocycles with aryl boronic acids

The palladium-catalyzed oxidative coupling of pyrido- and benzotriazol-1-yloxyquinazolines and -thienopyrimidines with aryl boronic acids in the presence of Pd(PPh(3))(4) and Cs(2)CO(3) under oxygen in DME containing 0.4-0.8% water for the preparation of heteroaryl ethers is described. These transformations of triazol-1-yloxy reagents demonstrate excellent O-chemoselective control under mild conditions and good yields. Mechanistic studies based on (18)O labeling indicate that phenols as intermediates in S(N)Ar reactions with ethers are formed in oxidative and nonoxidative pathways.

Dimethyl Sulfoxide Mediated Elimination Reactions in 3-Aryl 2,3-Dihalopropanoates: Scope and Mechanistic Insights

Dimethyl sulfoxide (DMSO) efficiently causes the reductive elimination of 3-aryl 2,3-dibromopropanoates to cinnamates with good yield. With 3-phenyl 2,3-dihalopropanoates, debromination is the major pathway providing 3-phenylacrylate derivatives in high yields, whereas dehydrobromination is a competing pathway with thiophene derivatives. 1H NMR, 81Br NMR, and MS techniques indicated the formation of brominated-DMSO, MeBr, and HBr as byproducts in this transformation with no evidence for the formation of Br2. The dual role of DMSO as a nucleophile and bromine scavenger accounts for the products formed in this reaction.

An Efficient Direct Amination of Cyclic Amides and Cyclic Ureas

[reaction: see text] An efficient one-step amination of cyclic amides and ureas has been developed. Treatment of cyclic amides and cyclic ureas with BOP in the presence of DBU in various solvents led to the formation of cyclic amidines and cyclic guanidines in good to excellent yields. Concise syntheses of biologically intriguing kinetin and potent kinase inhibitor olomoucin were thus achieved in just one and two steps, respectively.

The [4 + 3]-cycloaddition/quasi-Favorskii process. Synthesis of the carbocyclic core of tricycloclavulone

[reaction: see text] The [4 + 3]-cycloadduct derived from the reaction of 2,5-dibromocyclopentanone with cyclopentadiene was converted via a quasi-Favorskii rearrangement and ring-opening, ring-closing metathesis sequence to the carbocyclic core of the prostanoid tricycloclavulone.