Photoassisted Access to Enantiopure Conformationally Locked Ribofuranosylamines Spiro-Linked to Oxazolidino-Diketopiperazines.

N-Furoylated l-threonine-, serine-, or cysteine-based
aminoacetals are coupled with o-aminoketones or aldehydes
to offer rapid access to diverse enantiopure polyheterocycles possessing
conformationally locked aminoglycoside-containing molecular scaffolds.
The key step involves photogeneration of azaxylylenes which undergo
[4 + 4] or [4 + 2] cycloadditions to the tethered furoyl pendants.