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Routes to putative N-acyl-D-ala-D-ala surrogates, beginning with the conversion of 4-, 5-, and 6-membered lactones into 5-, 6-, and 7-membered cyclic hydroxamates, are reported. The key step of the synthesis is trimethylaluminium-promoted cyclization of an [omega]-aminooxyester. The 7-membered cyclic hydroxamate crystallizes in a chair conformation. Extension of the reaction sequence to homoserine or homoserine lactone leads to cyclocanaline and N-acylated cyclocanalines. The 4-phenylacetamido derivative of cyclocanaline crystallizes in a boat conformation. The attachment of a 2-carboxypropyl substituent to the ring nitrogen of a 4-acylaminocyclocanaline has been effected, prior to cyclization, by coupling of the acyclic aminooxyester precursor to the triflate of benzyl lactate or, after cyclization, by coupling to tert-butyl [alpha]-bromopropionate in the presence of potassium fluoride--alumina, followed by removal of the protecting group in each case. A six-membered homolog of the antibiotic lactivicin has been synthesized by the reaction of 4-phenylacetamidocyclocanaline with benzyl 2-oxoglutarate in the presence of carbodiimide, followed by hydrogenolysis. Starting with methyl 2,4-dibromo-2,4-dideoxy-L-erythronate, which is available in two steps from L-ascorbic acid, these reaction sequences have been applied to the stereospecific synthesis of a D-alanine derivative whose nitrogen atom is enclosed within a 3,4-disubstituted [1,2]oxazinan-3-one. Key words: D-ala-D-ala surrogate, cyclocanaline, homolactivicin, peptidoglycan, trimethylaluminium.

Objective: There is no useful tool to clinically predict the occurrence of osteoradionecrosis (ORN) of the mandible quantitatively. The aim was to investigate the risk factors, including different modalities of radiotherapy, for developing mandibular ORN in patients undergoing marginal mandibulectomy and postoperative radiotherapy.Methods: Between January 2006 and December 2012, 167 subjects who underwent marginal mandibulectomy and postoperative radiotherapy with different modalities were enrolled. The association of ORN with mandibular bone measurements and patient variables was analyzed, and a nomogram was established.Results: Fifteen (8.98%) of the 167 patients developed ORN during the follow-up period, and ORN was significantly associated with diabetes mellitus (DM), body mass index (BMI), remaining bone height, remaining bone height to original bone height ratio, resected bone height to original bone height ratio, and mandibular dose (P: < 0.001, 0.004, 0.042, 0.018, 0.010, 0.020, respectively). Interestingly, the risk of ORN had no significant difference between conformal and intensity modulation radiation therapy (P = 0.407). Multivariate analysis revealed that DM and resected bone height to original bone height ratio ≥ 50% were independent risk factors for postoperative ORN. A nomogram consisting of BMI, DM, resected bone height to original bone height ratio, mandibulotomy, and mandibular dose for predicting the ORN-free probability was established; and the c-index of the nomogram for ORN status was 0.803.Conclusion: A nomogram based on the risk factors was plotted to strengthen the prediction of ORN quantitatively. Surgeons should be more discrete regarding the treatment plan for patients with higher probability of ORN.Level Of Evidence: 3b Laryngoscope, 130:101-107, 2020. [ABSTRACT FROM AUTHOR]