Asymmetric Synthesis of α‐Allenylglycines

Abstract

The coupling of the homocuprate of the bislactim ether of cyclo‐(‐L‐Val‐Gly‐) (9) with primary propargyl halides produces the allenyl‐substituted bislactim ethers 11 in a highly diastereoselective manner, whereas the alkylation of the lithiated bislactim ether of cyclo‐(‐L‐Val‐Gly‐) yields the propargyl‐substituted bislactim ethers 12. Subsequent hydrolysisaffords, after protection of the amino group, the methyl α‐allenylglycinates 15, the α‐allenylglycines 16, and the methyl α‐propargylglycinates 17. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

How easy are the syntheses of allenes?

“…Groth et al developed an approach towards enantiomerically enriched a-allenylglycines 105 utilizing homocuprate of the bislactim ether of cyclo-(-L-Val-Gly-) 102 and primary propargyl halides 103 (Scheme 37). 86 This copper-catalyzed S N 2 0 substitution produces the allenyl-substituted bislactim ethers 104 in a highly diastereoselective manner, albeit, the yields are not high due to the formation of the S N 2 substitution products. Subsequent hydrolysis of the allenylsubstituted dihydropyrazines 104 affords the a-allenylglycines 105.…”

Copper-Catalyzed Reductive Ireland–Claisen Rearrangements of Propargylic Acrylates and Allylic Allenoates

“…The solvents DCM, THF, toluene, benzene, C 6 D 6 , and toluene- d 8 were distilled from CaH 2 and then dried over 4 Å MS. The propargylic and allylic alcohols for preparing corresponding propargylic ester 3 and allenic ester 6 were prepared according to the known literature − or were commercially available. Compounds 53 , 56 , and 61a were prepared according to the known literature.…”

C–H amination/cyclocarbonylation of allene carbamates: a versatile platform for the synthesis of α,β-unsaturated γ-lactams

“…The product was obtained as an inseparable mixture of stereoisomers (w2:1 approximate dr for CeH amination) in 31% as a thick, colorless oil using general procedure D. 1 H NMR (500 MHz, C 6 D 6 ) 13 43 (m, 6H), 0.84e0.98 (overlapping signals, 9H). 13 13 …”

“…4 , ceric ammonium nitrate, and phosphomolybdic acid in ethanol stain.1 H NMR and 13 C NMR spectra were obtained using Bruker-300, OD, respectively) 13. C NMR spectra were measured at either 125 MHz or 150 MHz on the same instruments noted above for recording 1 H NMR spectra.…”