An entry to 7-amino- and to 2-ethoxycarbonyl-5-dethia-5-oxa-cephams from 1,3-alkylidene-l-erythritol

Practical Method for the Absolute Configuration Assignment of tert/tert 1,2-Diols Using Their Complexes with Mo2(OAc)4

“…Cis-hydroxylation reaction of the respective oxacepham bearing an exo isopropylene group at C-7 gave an inseparable mixture of diols in a ratio of 4.5:1. The absolute configuration at the bridgehead carbon atom in the major product 14 was established to be (6 S ) by NMR and CD spectroscopies …”

“…The absolute configuration at the bridgehead carbon atom in the major product 14 was established to be (6S) by NMR and CD spectroscopies. 48 However, the absolute configuration at C-7 could not be ascribed unequivocally by these methods. Thus, we decided to apply the CD dimolybdenum methodology for this purpose.…”

A Holistic Approach to Determining Stereochemistry of Potential Pharmaceuticals by Circular Dichroism with β-Lactams as Test Cases

“…The absolute configuration at C6 carbon atom of tricyclic oxacepham derivative 10 , named according to IUPAC (2 R ,4a R ,5a S ,6 S ,9a S )-6-hydroxy-6-(10-hydroxy-10-methyl-ethyl)-2-phenyl-1,3,5-trioxa-8-aza-cyclobuta[b]decalin-7-one, was previously established by synthetic route, NMR and CD spectroscopies as (6 S ) [ 34 , 35 ]. The negative CE sign at 230 nm visible in its ECD spectrum corresponds to (6 S ) AC, correlating well with the helicity rule as well as the synthetic route and NMR data ( Figure 12 ).…”

“…Source of Investigated Compounds. Synthesis and full structural characterizations of compounds 1 [ 48 ], 4 [ 31 , 68 ], 5 [ 49 ], 6 [ 46 ], 7 [ 53 , 54 ], ent -7 [ 53 , 54 ], 8 [ 30 ], 9 [ 30 ] and 10 [ 34 ], have already been published. Synthetic details and spectroscopic characterization of compounds 2 and 3 are available in Supplementary Materials .…”

“…The set of discussed examples is closed by the β-lactam derivative 10 . Its AC at the bridgehead carbon atom was definitely established as (6 S ) by NMR and ECD spectroscopies [ 34 , 35 ]. However, assigning AC to the C7 carbon atom required applying another ECD method, known in the literature as the in situ dimolybdenum method.…”