Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• was dependent on the stereocontrolled Michael addition of the anion generated from crotyl phosphonamide 28f, which set three contiguous stereocenters in one step. Thus, addition of the Li anion of 28f to cyclopentenone 153 gave adduct 154 as a single diastereomer on a gram scale. Cleavage of the

Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of ¹³C chemical shifts

• Simone Di Micco,
• Angela Zampella,
• Maria Valeria D’Auria,
• Carmen Festa,
• Simona De Marino,
• Raffaele Riccio,
• Craig P. Butts and
• Giuseppe Bifulco

Beilstein J. Org. Chem. 2013, 9, 2940–2949, doi:10.3762/bjoc.9.331

• extend the application of NMR-derived interproton distances to a highly flexible molecular system with simultaneous assignment of four non-contiguous stereocenters. Chemical derivatization and quantum mechanical calculations of 13C on plakilactone G along with a plausible biogenetic interconversion

• configurational assignment of the C-7 and C-8 contiguous stereocenters through chemical derivatization. Thus, plakilactone G (1) was converted to the corresponding 7,8-O-isopropylidene derivative by treatment with 2,2-dimethoxypropane and a catalytic amount of p-TsOH. As reported in the literature [29], the

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• acid additive (Scheme 23). Avoiding the dehydration step, it is possible by this protocol to obtain thiochromans 45 bearing three contiguous stereocenters and a tertiary aldol structural motif with excellent enantioselectivities (96–99% ee) and yields (71–98%), and with good diastereocontrol (10:1 to

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• (MBH) carbonates with maleimides, which can efficiently construct functionalized cyclopentenes bearing three contiguous stereocenters in moderate to excellent yields and excellent diastereo- and enantioselectivities. A plausible mechanism has been also proposed on the basis of control experiments and

• + 2] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentene derivatives bearing three contiguous stereocenters in moderate to excellent yields along with excellent diastereo- and enantioselectivities. Results and Discussion In our previous work, it

• ] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentenes bearing three contiguous stereocenters in moderate to excellent yields and excellent diastereo- and enantioselectivities, and the product can be efficiently transformed into a cyclopentane containing