Novel compounds and method for preparing 3-methylcephams

A compound of Formula IIA:

• 20
• wherein:
• R is a carboxylic acid protecting group;
• R1 is a group of the formula;
• 21
• R2 is C2-C4 alkenylene, C2-C4 alkylene, 1,2-phenylene, or 1,2-cyclohexenylene;
• R2′ is C1-C3 alkyl, C1-C6 haloalkyl, C1-C3 alkoxy, or 2,2,2-trichloroethoxy;
• R3 is hydrogen, C1-C3 alkyl, halomethyl, cyanomethyl, 3-(2-chlorophenyl)-5-methylisoxazol-4-yl, benzyloxy, 4-nitrobenzyloxy, 2,2,2-trichloroethoxy, tert-butoxy, 4-methoxybenzyloxy, phenyl, substituted phenyl, a group of the formula R0—(Q)m—CH2—, a heteroarylmethyl group of the formula R″CH2—, or a substituted group of the formula
• 22
• R0 is phenyl, substituted phenyl, 2-thienyl, 3-thienyl, or 1,4-cyclohexyldienyl;
• R″ is 2-furyl, 3-furyl, 2-thiazolyl, or 5-isoxazolyl;
• m is 0 or 1,
• Q is O or S;
• W is protected hydroxy, or protected amino;
• Y is hydrogen, acetyl, or nitroso;
• R10 is C1-C6 alkyl, C1-C6 polyfluoroalkyl, C3-C6 cycloalkyl, adamantyl, phenyl, substituted phenyl, phenyl(C1-C3 alkyl), diphenylmethyl, or substituted phenyl(C1-C3 alkyl), or a group of the formula
• 23
• Z is solid polymer support;
• and
• Z1 is one or two groups independently selected from the group consisting of hydrogen, halo, hydroxy, protected hydroxy, nitro, cyano, trifluoromethyl, C1-C4 alkyl, and C1-C4 alkoxy.