1-(4-Methoxybenzyl)-6-((trimethylsilyl)ethynyl)-1-(4-MethoxybeH-pyrido[2,3-b][1,4]oxazin-2(3H)-one1-(4-Methoxybenzyl)-6-((trimethylsilyl)ethynyl)-1H-pyrido[2,3-b][1,4]oxazin-2(3H)-one1-(4-Methoxybenzyl)-6-((trimethylsilyl)ethynyl)-1H-pyrido[2,3-b][1,4]oxazin-2(3H)-one