Table 1.

Synthesis of compounds 1–3a–g.

U-5C-4CR					N-de-tert-butylation		Cyclocondensation
Ugi adduct	Amino acid	Carbonyl component	Yield	Dr a	Yield 1→2	Yield 1→3	Yield 1→3
(2S,2S)-1a	L-Proline	Benzaldehyde	64% b	4:1	62%	- c	65% d
(2S,2S)-1b	L-Proline	Phenylacetaldehyde	54% b	4:1	61%	-	69% d
(2S,2S)-1c	L-Pipecoline	Phenylacetaldehyde	60% b	4:1	43%	-	55% d
(2S,2S)-1d	L-Proline	Phenylacetone	38% b	1:1	46%	24%	88% d
(2S)-1e	L-Proline	1,3-Diphenylacetone	17%	-	-	46%	-
(2S)-1f	L-Proline	Acetone	61%	-	33%	36%	95%
(2S)-1g	L-Proline	Cyclopentanone	60%	-	26%	70%	-

^a Dr of (2S,1S)-1/(2S,1R)-1 astimated by ¹H analyses of the crude postreaction mixtures (1a–c) or LC/MS (1d); ^b Sum of (2S,1S)-1 and (2S,1R)-1 diastereoisomers; ^c Not applicable; ^d Yield of pure diastereoisomers.