276
S. Breitenlechner, P. Selig, T. Bach
Eventually, the configuration proof was based on a comparison of calculated and measured CD spectra (Scheme 17). The absolute configuration is in line with a coordination of the substrate to the template and
a subsequent cyclisation of the α-aminoalkyl radical to the quinolone
core from the most accessible face, that opposite to the shield.
5
Summary
In summary, the utility of hydrogen bonds for controlling the absolute
configuration in photomediated reactions has been demonstrated. Despite the simple binding motif, a number of reactions have been shown
to proceed enantioselectively (up to 99% ee). The complexing agent,
which is used in stoichiometric or superstoichiometric amounts, can be
repeatedly recovered and allows consequently a multiplication of chirality. Chirality turnover in a single reaction vessel has so far been observed for compound (+)-12 in the radical cyclisation 27→trans-29 and
for sensitiser (–)-40 in the PET-catalysed reaction 35→36. Further work
is directed towards application of this methodology in more complex
syntheses and towards a development of more efficient catalytic transformations.
References
Achenbach TV, Slater EP, Brummerhop H, Bach T, Müller R (2000) Inhibition
of cyclin-dependent kinase activity and induction of apoptosis by preussin
in human tumour cells. Antimicrobiol Agents Chemother 44:2794–2801
Aechtner T, Dressel M, Bach T (2004) Hydrogen bond mediated enantioselectivity of radical reactions. Angew Chem 116:5974–5976, Angew Chem Int
Ed 43:5849–5851
Aichaoui H, Lesieur I, Hénichart JP (1990) Unequivocal preparation of 4- and
5-acyl-2-aminophenols. Synthesis 679–680
Bach T, Bergmann H (2000) Enantioselective intermolecular [2+2]-photocycloaddition reactions of alkenes and a 2-quinolone in solution. J Am
Chem Soc 122:11525–11526
Bach T, Brummerhop H (1998) Unprecedented facial diastereoselectivity in the
Paternò-Büchi reaction of a chiral dihydropyrrol—A short total synthesis of
(+)-preussin. Angew Chem 110:3577–3579, Angew Chem Int Ed 37:3400–
3402
S. Breitenlechner, P. Selig, T. Bach
Eventually, the configuration proof was based on a comparison of calculated and measured CD spectra (Scheme 17). The absolute configuration is in line with a coordination of the substrate to the template and
a subsequent cyclisation of the α-aminoalkyl radical to the quinolone
core from the most accessible face, that opposite to the shield.
5
Summary
In summary, the utility of hydrogen bonds for controlling the absolute
configuration in photomediated reactions has been demonstrated. Despite the simple binding motif, a number of reactions have been shown
to proceed enantioselectively (up to 99% ee). The complexing agent,
which is used in stoichiometric or superstoichiometric amounts, can be
repeatedly recovered and allows consequently a multiplication of chirality. Chirality turnover in a single reaction vessel has so far been observed for compound (+)-12 in the radical cyclisation 27→trans-29 and
for sensitiser (–)-40 in the PET-catalysed reaction 35→36. Further work
is directed towards application of this methodology in more complex
syntheses and towards a development of more efficient catalytic transformations.
References
Achenbach TV, Slater EP, Brummerhop H, Bach T, Müller R (2000) Inhibition
of cyclin-dependent kinase activity and induction of apoptosis by preussin
in human tumour cells. Antimicrobiol Agents Chemother 44:2794–2801
Aechtner T, Dressel M, Bach T (2004) Hydrogen bond mediated enantioselectivity of radical reactions. Angew Chem 116:5974–5976, Angew Chem Int
Ed 43:5849–5851
Aichaoui H, Lesieur I, Hénichart JP (1990) Unequivocal preparation of 4- and
5-acyl-2-aminophenols. Synthesis 679–680
Bach T, Bergmann H (2000) Enantioselective intermolecular [2+2]-photocycloaddition reactions of alkenes and a 2-quinolone in solution. J Am
Chem Soc 122:11525–11526
Bach T, Brummerhop H (1998) Unprecedented facial diastereoselectivity in the
Paternò-Büchi reaction of a chiral dihydropyrrol—A short total synthesis of
(+)-preussin. Angew Chem 110:3577–3579, Angew Chem Int Ed 37:3400–
3402