NEW MATERIAL:A compound shown by formula I [R1 is hydroxyalkyl which may be protected; R2 is alkyl; R3 is R1, H or alkyltrisubstituted silyl; R4 is (substituted)OH or (substituted)amino or a salt thereof.

EXAMPLE: 5-Benzyloxy-2-[1-tertiary butyldimethylsilyloxyethyl)-3-hydroxy-N-me thoxy-4-methylpentanamide.

USE: An intermediate for producing an 1-alkylcarbapenem compound having strong antibacterial action on many pathogenic bacteria.

PREPARATION: For example, a compound shown by formula II is reacted with a compound shown by formula III (R4 is substituted OH; R5 is OH-protecting group) to give a corresponding compound shown by formula I.