Photolabile dendrimers using o-nitrobenzyl ether linkages

Organic Letters

Volumn 2, Issue 4, 2000, Pages 511-512

  Smet, Mario ^a,b   Liao, Li Xin ^a   Dehaen, Wim ^a,b   McGrath, Dominic V ^a  

^a University of Arizona   (United States)

^b UNIVERSITY OF LEUVEN   (Belgium)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001917031     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol991373b     Document Type: Article

References (32)

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27. Satisfactory characterization data were obtained for all new compounds reported (see Supporting Information).
28. This 1:2:1 ratio of peaks is consistent with a statistical mixture of 1:3 homochiral/heterochiral diastereomers. The ratio of the same peaks in 3b was closer to 2:4:3, consistent with a 1:2 ratio of diastereomers. The stereoisomer ratio for 3c was again 1:3. Despite the apparent implication for stereoselectivity in the formation of 3b, we must note that these peaks are barely resolved, so the ratios are at best approximate (see Figure 1b). Any conclusions regarding inherent stereoselectivity in the coupling reactions leading to 3a-c are unfortunately precluded until such time that these ratios can be more accurately determined. For an example of stereoselectivity in the preparation of chiral dendrimers see: Murer, P. K.; Lapierre, J.-M.; Greiveldinger, G.; Seebach, D. Helv. Chim. Acta 1997, 80, 1648-1681.
29. 3, THF).
30. 1H NMR spectrum, provided by Dr. C. P. Holmes of Affymax Research Institute, Palo Alto, CA, of an authentic sample of 4,5-dimethoxy-2-nitrosoacetophenone. In the presence of oxygen a peak appears at 2.48 ppm which is presumably o-nitroacetophenone formed upon oxidation of initially formed o-nitrosoacetophenone.
31. 2, 500 Å, 1000 Å, 10 000 Å Jordi DVB columns), but the resolution is insufficient to fully separate the individual fragments.
32. n → nM) where polymer subunits and monomer units are distinct chromophores. See: Cohen, M. D.; Fischer, E. J. Chem. Soc. 1962, 3044-3052.