Synthesis and characterisation of muramic acid 1′,2-lactam-β-(1→4)-d-glucosamine derivatives related to repeating units of bacterial spore cortex

Localization of the attachment site of oligoglucans to Mesorhizobium loti HAMBI 1148 murein.

“…1, which should give muramyl residues (1→4) linked with 2,5-anhMan or short oligoglucans. To increase the efficiency of the formation of δ-lactam rings between the amino group at C 2 and the lactoyl residue, esterification of the carboxyl group of MurNAc was carried out (Keglević et al, 1998). Nitrous deamination which is known to be capable of breaking down the chitin (Runham, 1961), was used to depolymerise murein glycan chains.…”

“…For this procedure, the N-deacylated murein glycan, containing both neutral and aminosugars, was esterified (0.25 M methanolic HCl, 80 o C, 3.5 h; sample concentration 20 mg/ml), rotary evaporated, distilled twice with MeOH, and freezedried. The esterified muramic acid residues (in oligoglycan fragments) were subjected to lactamization with hydrazine acetate in dry methanol (Keglević et al, 1998) at 65 o C for 36 h in a Pyrex screw-cap test tube with a Teflon-lined cap. After cooling of the material, 5 volumes of acetone were added to precipitate murein glycan and to decompose hydrazine.…”

A Historical Perspective on Crystallography in Croatia and the Career of Biserka Kojić-Prodić from the Viewpoint of the CSD

“…Acta 2018, 91(2), 149-152 has a Z' = 2 and only very tiny plates could be obtained (Rfactor of 17 %, CSD refcode BEFQUY). [16] This pair of structures really capture the challenges associated with experimental crystallography and the need to obtain structures of appropriate precision for the research in question. If you want to study charge density, you need incredibly precise, high resolution data; if you are simply aiming to prove the 3D structure and conformation of the compounds studied then a different level of precision is required.…”

Stereoselective Glycosylation of Glucosamine: The Role of the N‐Protecting Group

“…The corresponding glucosamine derivative could be prepared by azido nitration of a glycal (14) [66] (Scheme 6 A) or by diazotransfer reaction using triflic azide (Scheme 6 B) [67] or another diazotransfer reagent. [68] The synthesis of 2-azido glucosamine donors is also possible by the inversion of the configuration of the 2-hydroxy group from a mannose derivative (20), but this method requires a multistep reaction sequence (Scheme 6 C). [69] Table 8.…”

“…Selected examples of N ‐Phth‐protected glucosamine donors and glycosylations using various acceptor moieties are shown in Table 2. Glycosylations using N ‐Phth trichloroacetimidates are usually carried out in dichloromethane and can be promoted by catalytic amounts of trimethylsilyl trifluoromethanesulfonate (TMSOTf)14, 16, 17, 18 or AgOTf20 (Table 2, entries 1–3) as well as BF 3 ⋅OEt 2 14b. N ‐Phth thioglycoside donors like STol,15 SPh,21 SEt,22 S i Pr,23 and S‐benzoxazolyl (S‐Box)3 can be activated by NIS/TfOH,22, 24 NIS/TESOTf,21 or AgOTf in the presence of PTSCl ( p ‐toluenesulfonyl chloride) (Table 2, entry 4),15a NIS/TMSOTf (Table 2, entries 5 and 6),15b, 23 BSP/Tf 2 O/DTBMP (Table 2, entry 7), [25] or MeOTf 3.…”