RESUMO
Long-chain polyamides (polyethyleneamides) were prepared from polyethylenes bearing in-chain carbonyl groups (polyethyleneketones) by the oxime formation and successive Beckmann rearrangement. (Diethylamino)sulfur trifluoride (DAST) was utilized as a promoter, which allowed mild conversion of the oxime group in spite of low solubility of the polymers. The polyethyleneamide exhibited different tensile property compared to a commercial HDPE.
RESUMO
Fluorination of oximes with the relatively mild diethylaminosulfur trifluoride/tetrahydrofuran (DAST-THF) system affords imidoyl fluorides. These compounds were isolated, and their structures were confirmed by X-ray single-crystal structure analysis. Reaction of imidoyl fluorides with various nucleophiles efficiently afforded amides, amidines, thioamides, and amine derivatives in high yields. Furthermore, one-pot reaction of in situ generated imidoyl fluorides from oximes was also applicable to efficient synthesis of these products. The oxime stereochemistry and acid-labile protecting group remained intact in this system.
RESUMO
BACKGROUND: Preoperative chemoradiotherapy is the standard treatment for patients with locally advanced rectal cancer, although tumor responses vary widely; some patients may achieve a pathologic complete response rate (pCR) after chemoradiotherapy. Controversy exists with regard to the efficacy of different preoperative combination chemotherapy regimens and neoadjuvant chemoradiotherapy, compared with chemoradiotherapy alone. METHODS: PubMed, the Cochrane Library, and Embase databases were searched for comparative studies of patients with locally advanced rectal cancer that were published between January 1991 and January 2016. Efficacies of different preoperative combination chemotherapy regimens and neoadjuvant chemoradiotherapy (group A) were compared with chemoradiotherapy alone (group B) in a meta-analysis using Review Manager v5.2. RESULTS: Three prospective randomized controlled trials and two prospective nonrandomized controlled trials comprising 444 cases were eligible for analysis. No significant difference was detected in the rate of pCR (50/223, 22.4% versus 35/223, 15.7%; relative risk, RR: 1.42 [95% confidence interval, CI: 0.97-2.09], p = 0.07) between the two groups. The rate of tumor regression was similar for both groups (122/203, 60.1% versus 111/203, 54.7%; RR: 1.11 [95% CI: 0.94-1.29], p = 0.22). CONCLUSIONS: Adjuvant chemotherapy with preoperative chemoradiotherapy did not significantly improve the rate of pCR nor the rate of T and N downstaging.
