Patent ID: 7078399

Claim:
A compound of formula I: wherein X 1 represents an oxygen atom or a sulfur atom; R 1 represents a hydrogen or an acetyl group; R 2 represents a hydrogen or hydroxyl group; and R 3 represents a hydrogen atom or a group expressed by the formula: wherein each of R 4 and R 5 is, independently, an alkyl group having 1 to 7 carbon atoms, or R 4 and R 5 combine to form a 3–8 membered cyclic system, or R 3 represents a group expressed by the formula: in which g represents an integer between 1 and 3; or R 3 represents a group expressed by the formula: wherein each of R 6 and R 7 is, independently, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, X 2 represents an oxygen atom, a sulfur atom, a carbonyl group, or X 2 represents a group expressed by the formula: in which each of R 8 and R 9 is, independently, a hydrogen atom, or an alkyl group having 1 to 3 carbon atoms, or R 8 and R 9 , in combination with each other, represent —(CH 2 ) k — in which k represents an integer between 1 and 4; or X 2 represents a group expressed by the formula: in which m represents 0 or 1, R 10 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or —(CH 2 ) n X 3 in which n represents an integer between 1 and 4, and X 3 represents an alkoxy group having 1 to 3 carbon atoms, a vinyl group, an ethynyl group, or X 2 represents a group expressed by the formula: