1. A mild and efficient method for the preparation of guanidines
2. Reactions performed at higher concentrations were incomplete due to gel formation
3. Reactions with other acylating agents gave mixed results. Acylation with chloroformate derivatives, such as methyl chloroformate or benzyl chloroformate, gave a mixture of N and S acylated products. In addition, attempted acylation with dibenzyl dicarbonate gave products in which alkylation (incorporation of a benzyl residue) was competitive with acylation
4. N,N'-bis-tert-butoxycarbonylthiourea 3 was found to be >95% pure by HPLC: YMC S-3 ODS (C-18) 6.0 × 150 mm, eluting with methanol, water and phosphoric acid, detected at 217 nm.