| 摘要 |
<p>Compounds having the structural formula WHEREIN R is methyl, ethyl, furfuryl, IN WHICH R1 is hydrogen or methyl; R2 is phenyl, acetyl or propionyl when R1 is hydrogen and R2 is methyl when R1 is methyl; R3 is hydrogen or C1-C6 alkyl; R4 is C1-C6 alkyl, phenyl or C1-C3 carboalkoxy; and R5 is hydrogen or C1-C6 alkyl.</p> |
