TY - JOUR
T1 - 2-Halo-diketopiperazines as chiral glycine cation equivalents
AU - Bull, Steven D.
AU - Davies, Stephen G.
AU - Garner, A. Christopher
AU - Savory, Edward D.
AU - Snow, Emma J.
AU - Smith, Andrew D.
PY - 2004/12/13
Y1 - 2004/12/13
N2 - A range of (2S,5S)-5-isopropyl-2-halo-N,N′-bis-(p-methoxybenzyl)- piperazine-3,6-diones 8 (Cl), 11, 12 (F) and 13 (Br) have been prepared, either via electrophilic halogenation of the corresponding lithiated diketopiperazine, or via transhalogenation from fluoro-11 and 12. The product distribution and stereoselectivity of additions of allyltrimethylsilane, sodium thiophenolate and a range of organomagnesium reagents to chloro 8 are reported. In the reactions with Grignard reagents the observed stereo- and regioselectivities are dependent on the reagent employed, with C-3 carbonyl addition products predominating upon addition of allyl or methylmagnesium chloride and stereodivergent formal C-2 addition predominating with benzyl or isopropylmagnesium chloride. A model to account for the different reactivity and stereoselectivity in these reactions is proposed.
AB - A range of (2S,5S)-5-isopropyl-2-halo-N,N′-bis-(p-methoxybenzyl)- piperazine-3,6-diones 8 (Cl), 11, 12 (F) and 13 (Br) have been prepared, either via electrophilic halogenation of the corresponding lithiated diketopiperazine, or via transhalogenation from fluoro-11 and 12. The product distribution and stereoselectivity of additions of allyltrimethylsilane, sodium thiophenolate and a range of organomagnesium reagents to chloro 8 are reported. In the reactions with Grignard reagents the observed stereo- and regioselectivities are dependent on the reagent employed, with C-3 carbonyl addition products predominating upon addition of allyl or methylmagnesium chloride and stereodivergent formal C-2 addition predominating with benzyl or isopropylmagnesium chloride. A model to account for the different reactivity and stereoselectivity in these reactions is proposed.
UR - http://www.scopus.com/inward/record.url?scp=9944263397&partnerID=8YFLogxK
U2 - 10.1016/j.tetasy.2004.11.022
DO - 10.1016/j.tetasy.2004.11.022
M3 - Article
AN - SCOPUS:9944263397
SN - 0957-4166
VL - 15
SP - 3989
EP - 4001
JO - Tetrahedron Asymmetry
JF - Tetrahedron Asymmetry
IS - 24
ER -