L,3-Selenazol-4-one derivatives

Dihydro-l,3-selenazol-4-one derivatives 31 are prepared by the reaction of primary selenoamides with a-haloacyl halides in the presence of pyridine. The cyclization reaction is thought to involve an Sn2 substitution reaction. Steric factors at the a-position of the carbonyl carbon of a-haloacyl halides slow the attack by selenium (Equation 16) <2003HAC106, 2002S195>. 

Table 1 The structure-activity relationships of the l,3-selenazol-4-one derivatives 19-24 against mushroom tyrosinase [46]...

Koketsu M et al. (2002) Inhibitory effects of l,3-selenazol-4-one derivatives on mushroom tyrosinase. Chem Pharm Bull (Tokyo) 50(12) 1594-1596 Khan MT et al. (2005) Structure-activity relationships of tyrosinase inhibitory combinatorial hbrary of 2,5-disubstituted-l,3,4-oxadiazole analogues. Bioorg Med Chem 13(10) 3385-3395... 

Koketsu et al. (2002) reported the DOPAoxidase activities of the 1,3-selenazol-4-one derivatives 19-24 against mushroom tyrosinase [46]. All of these compounds exhibited 33.4-62.1% inhibition of DOPAoxidase activity at a concentration of 500 p,M. Their inhibitory effects were higher than that of ko-jic acid (31.7%) [46]. 2-(4-Methylphenyl)-l,3-selenazol-4-one (19) exhibited the most potent inhibitory effect among them in a dose-dependent manner. Enzyme kinetic studies showed that compound 19 showed competitive in-... 

Selenourea and l,3-dichloropropan-2-one yield 2-amino-4-chloromethylselenazole hydrochloride (59) which was subsequently acetylated to give (60). Sodium diethyl for-mamidomalonate reacts with the acetamido compound (60) to give the protected amino acid derivative (61). Hydrolysis of (61) affords ( )-/3-(2-amino-l,3-selenazol-4-yl)alanine (62 Scheme 22) (81JHC205). 

Selenazole derivatives have been prepared from 6-methyl-3-propargylseleno-l,2,4-triazin-5-one via copper-catalyzed, or silica gel and thionyl chloride-catalyzed, cyclization. The reaction affords two kinds of selenazole derivatives 91, 92 in moderate yields. No cyclization takes place in the absence of the catalyst (Equation 27) <2001PS87, 1998IJB587>. 

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