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18.13.1.1.11 Method 11: Reaction of Guanidines with Alcohols or Activated Alcohols

DOI: 10.1055/sos-SD-018-01264

Berlinck, R. G. S.; Kossuga, M. H.; Nascimento, A. M.Science of Synthesis, (2005181106.

The reaction of guanidine or guanidine derivatives with alcohols or activated alcohols (in particular 4-toluenesulfonates and methanesulfonates) has been known since the 1960s. Two examples illustrate pioneering applications of this method. In the first case, a substituted guanidine is formed in situ by reaction of aniline with a cyanamide pyranosil derivative. The substituted guanidine reacts directly with a vicinally attached methanesulfonate, in good yield.[‌154‌] In the second example, guanidine hydrochloride is reacted with (2,3-dihydrobenzo[b][1,4]dioxin-2-yl)methyl 4-toluenesulfonate in the presence of sodium hydride to give [(2,3-dihydrobenzo[b][1,4]dioxin-2-yl)methyl]guanidine also in good yield.[‌155‌] Bis(tert-butoxycarbonyl)-protected or bis(benzyloxycarbonyl)-protected guanidines react with chiral alcohols via a Mitsunobu protocol to give the corresponding optically active guanidines 61 as single enantiomers in excellent yields (Scheme 30).[‌156‌] Different guanidino amino acids have also been synthesized by a similar Mitsunobu protocol, in yields ranging from moderate to excellent.[‌128‌] Applications of the preparation of guanidines using alcohols, frequently using Mitsunobu conditions, include the synthesis of dianhydrohexitol integrin antagonists,[‌157‌] as well as in the synthesis of different alkaloids[‌9‌‌12‌] such as batzelladine D,[‌158‌] batzelladine A,[‌159‌,‌160‌] in the synthesis of ptilomycalin A analogues,[‌161‌] and in the synthesis of (2S,3R)-capreomycidine.[‌162‌]

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