Alpha-bromo-alpha,alpha-difluoroallyl derivatives as synthetic intermediate: nucleophilic substitution of alpha-bromo-alpha,alpha-difluoroallyl derivatives in the presence of palladium catalysts.

The palladium catalyzed nucleophilic substitution of alpha-bromo-alpha,alpha-difluoroallyl derivatives turned out to be an efficient method for the preparation of several fluorinated organic molecules. Several soft carbon nucleophiles regioselectively reacted with 3-bromo-3,3-difluoropropene (BDFP) to give the 3-substituted 1,1-difluoroalkenes. Phenylzinc chloride and tributylphenyltin afforded 1-fluoro-1,3-diphenylpropene. The radical bromination of 3-substituted 1,1-difluoroalkenes provided 1-substituted BDFPs, and a 1-substituted BDFP reacted with carbon nucleophiles to give 1,3-disubstituted 3,3-difluoroalkenes. For the reaction of nitrogen nucleophiles with BDFP, an amine and the sodium salts of the carbamates reacted with BDFP at the gamma-position. However, the sodium salts of the sulfoneamide predominantly attacked at the alpha-position.

[New methods of constructing fluorinated organic compounds and their application].

This review summarizes several effective synthetic methods of fluorinated organic compounds developed by our group. Two topics have been described in this review. The first topic describes novel fluorinations using diethylaminosulfur trifluoride (DAST). The treatment of tertiary cyclopropyl silyl ethers with DAST caused ring opening and produced allylic fluorides. The reaction of DAST with a tertiary cyclobutanol provided a fluorocyclobutane, a (fluoromethyl)cyclopropane or a homoallylic fluoride. DAST reacted with cyclic ketoximes bearing substituent(s) that can stabilize a carbocation to cause the fluorinative fragmentation which produces fluorinated carbonitrile. The second topic describes the novel syntheses of organic compounds containing the difluoromethylene moiety using fluorinated building blocks. The indium-mediated coupling of aldehydes with 3-bromo-3,3-difluoropropene gives alpha,alpha-difluorohomoallylic alcohols in high yields. alpha,alpha-Difluorohomopropargylic alcohols were also obtained from the indium-mediated coupling of aldehydes with alpha-bromo-alpha,alpha-difluoropropargyl compounds. In the presence of a palladium(0) catalyst, several nucleophiles regioselectively reacted with 3-bromo-3,3-difluoropropene at its gamma-position, and reacted with 1-substituted-3-bromo-3,3-difluoropropenes at their alpha-position. (+)-(R)-1-Amino-2,2-difluorocyclopropane-1-carboxylic acid was synthesized via the lipase-catalyzed asymmetric acetylation of a pro-chiral diol as a key step.

Fluorinative Beckmann fragmentation: fluorinative alpha-cleavage of cyclic ketoximes by diethylaminosulfur trifluoride.

Diethylaminosulfur trifluoride reacted with cyclic ketoximes bearing substituent(s) that can stabilize a carbocation to cause fluorinative fragmentation, affording fluorinated carbonitrile. Ketoximes lacking such substituents afforded complex mixtures. However, the introduction of a sulfur functionality, which can stabilize a carbocation and can be easily removed from the reaction products, into the ketoxime was effective for producing the fluorinative fragmentation.

[Appearance of extrahepatic lesions in the superior lip and orbit of a patient with liver metastases of gastric cancer following partial response by hepatic arterial infusion chemotherapy].

A 76-year-old man was totally gastrectomized in June, 1996 for advanced gastric cancer. In February, 1997, multiple liver metastases were found by abdominal CT scan, and hepatic arterial infusion chemotherapy was started with 5-FU, EPI and MMC by an implantable reservoir indwelled via the left subclavian artery. This treatment was judged to have led to a partial response because reduced focus size of the liver metastasis was revealed by CT scan and levels of tumor markers decreased significantly. However, metastatic foci were found in the skin of the superior lip and the orbit in December 1997. He was treated with a variety of therapies, but died in January, 1998. Many cases with metastatic hepatic cancer have a poor prognosis because of the appearance of extrahepatic lesions in spite of the fact that a partial response can be obtained by hepatic arterial infusion chemotherapy. The present case was unique since extrahepatic lesions appeared at very rare sites such as the superior lip and the orbit.

alpha-Tocopherol protects against radical-induced injury in cultured neurons.

The effect of alpha-tocopherol on neurons in protecting against radical-induced injuries caused by cumene hydroperoxide was assessed using a culture system. Structural and biochemical deteriorations in both clonal neuroblastoma cells and primary cultured neurons were induced by cumene hydroperoxide. These deteriorative changes were prevented prevented by pretreatment of alpha-tocopherol. Since simultaneous supplementation of alpha-tocopherol and cumene hydroperoxide had limited protective effects, prophylactic administration of alpha-tocopherol for risk patients with brain diseases concerned with damages induced by free radical is recommended to hamper the progression of neuronal impairment after attacks.

Charge isomers of urinary bikunin (trypsin inhibitor).

It was observed that the purified urinary bikunin (trypsin inhibitor) consisted of four major isomers with different electric charges which could be separated by HPLC using a Mono Q column. These isomers revealed the same antitrypsin activity and did not show any differences in the apparent molecular weight by SDS-PAGE, amino-acid composition, N-terminal amino-acid sequence (1-40) and C-terminal amino acid (Leu). The contents of sialic acid and uronic acid were also identical among these isomers. However, analysis of chondroitin sulfate revealed all the glycosaminoglycan chains of these isomers were undersulfated, comprising nonsulfated and 4-sulfated disaccharide units, and 4-sulfated disaccharide unit ratio varied among these isomers. After the chondroitin ABC lyase digestion, all the isomers were eluted at the same position on a Mono Q column chromatography. These results indicated that charge isomers of urinary bikunin was attributed to the difference on sulfation ratio in a glycosaminoglycan chain.

Synthesis of a potent rhodomycin, oxaunomycin, and its analogs.

Oxaunomycin (3) and its regioisomer (6) were synthesized by employing regioselective glycosidations of the C-7 hydroxyl group of 10-O-acetyl-beta-rhodomycinone (16) and the C-10 hydroxyl group of the C-7,9-O-phenylboronate (14), respectively, in the presence of trimethylsilyl trifluoromethanesulfonate. Under the Königs-Knorr conditions, 16 was also glycosidated to provide a fluoro sugar analog (7).

Synthetic anthracyclines: regiospecific total synthesis of D-ring thiophene analogues of daunomycin.

The key anhydride 2-acetoxy-[2-carboxy-5-(trimethylsilyl)thiophen-3-yl]acetic acid anhydride (8), prepared from (2-carboxythiophen-3-yl)acetic acid (5), underwent a strong base-induced cycloaddition reaction with the chloroquinone acetal (11) to give the 7,7-ethylenedioxy-2-trimethylsilyl-6,7,8,9- tetrahydroanthra[2,3-b]thiophene-5,10-dione (12) regioselectively. Similarly, the regioisomeric 8,8-ethylenedioxy-2-trimethylsilyl-6,7,8,9-tetrahydroanthra[2,3-b] thiophene- 5,10-dione (30) was obtained by the strong base-induced cycloaddition reaction of 8 with the chloroquinone acetal (29). These cycloadducts (12 and 30) were converted to D-ring thiophene analogues (28 and 38) of daunomycin (1a). Another D-ring thiophene analogue (42) which has a trimethylsilyl substituent in the D-ring was also prepared.

Synthetic anthracyclines: regiospecific total synthesis of a D-ring indole analogue of daunomycin.

The 4-methoxy-5-methylpyrano[4,3-b]indole-1,3(4H,5H)-dione (9), prepared from methyl 3-methoxycarbonyl-1-methylindol-2-yl acetate (6), underwent a strong base-induced cycloaddition reaction with 2-chloro-6,6-ethylenedioxy-5,6,7,8-tetrahydro-1,4-naphthoquinone (11) to give the tetrahydronaphtho[2,3-b]carbazole-7,12-dione (10), regioselectively. The cycloadduct (10) was successfully converted to a D-ring indole analogue of daunomycin (1a).