A photochemical route to 3- and 4-hydroxy derivatives of 2-aminocyclobutane-1-carboxylic acid with an all-cis geometry

Short gram scale syntheses of both enantiomers of 2-amino-3-hydroxycyclobutane-1-carboxylic acid and of 2-amino-4-hydroxycyclobutanecarboxylic acid with an all-cis geometry are described. The sequences feature highly endo-selective [2+2]-photocycloaddition reactions followed by fully regioselective ring opening / Hofmann rearrangement / nitrogen protection, in a consecutive or one-pot protocol, followed by efficient resolution using a chiral oxazolidinone.