Efficient Microwave Assisted Syntheses of 2,5-Diketopiperazines in Aqueous Media

Abstract

Aqueous in situ one-pot N-Boc-deprotection-cyclization of Nα-Boc-dipeptidyl-tert-butyl and methyl esters under microwave irradiation afforded 2,5-diketopiperazines (DKPs) in excellent yields. This protocol is rapid, safe, environmentally friendly, and highly efficient, and showed that the tert-butoxy moiety is also an excellent leaving group for these cyclizations.

Synthesis of Peptides and Pyrazines from β‐Amino Alcohols through Extrusion of H2 Catalyzed by Ruthenium Pincer Complexes: Ligand‐Controlled Selectivity

“…insoluble solid, which precipitated from the reaction mixture and was isolated by filtration and dried under vacuum to give 78 % of (3S,6S)-3,6-diisopropylpiperazine-2,5-dione 7 d (Table 1, entry 4). The optical rotation of the pure product (À528) was essentially the same as reported [24] (À54.88). Thus, under the described experimental conditions, no racemization took place.…”

Synthesis of Peptides and Pyrazines from β‐Amino Alcohols through Extrusion of H2 Catalyzed by Ruthenium Pincer Complexes: Ligand‐Controlled Selectivity

“…The optical rotation of the pure product (À528) was essentially the same as reported [24] (À54.88). Thus, under the described experimental conditions, no racemization took place.…”

“…The reaction of (S)-2-amino-3-phenylpropan-1-ol and 1 in 1,4-dioxane at reflux led to 90 % conversion and isolation of the corresponding (3S,6S)-3,6-dibenzylpiperazine-2,5-dione [24] 7 e in 72 % yield without racemization (Table 1, entry 5 and the Supporting Information). The reaction of 2-amino-2-methylpropan-1-ol under the same conditions gave 100 % conversion with isolation of the corresponding cyclic dipeptide 3,3,6,6-tetramethylpiperazine-2,5-dione 7 f in 92 % yield (Table 1, entry 6).…”

γ-Turn Mimicry with Benzodiazepinones and Pyrrolobenzodiazepinones Synthesized from a Common Amino Ketone Intermediate

“…XXXX, XXX, XXX−XXX B ketoaldehydes 13 at 150°C for 5−10 min and chromatography. 31 Pyrrolobenzodiazepinones 4 were also prepared from benzodiazepinones 6 in 44−77% yields by ozonolysis in CH 2 Cl 2 /MeOH (1:1) at −78°C, reduction of the ozonide with excess dimethyl sulfide, and chromatography on silica gel (Scheme 1). Attempts failed, however, to prepare pyrrolobenzodiazepinone 4f by oxidation of olefin 13f using sodium periodate/osmium tetraoxide.…”