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The increasing demand for soilless media for horticultural crop production and the rising environmental concerns about the use of non-renewable resources such as peat as substrate has led to the search for alternative materials as constituents of growing media, such as waste organic by-products. Also, biogas production through the anaerobic digestion of organic wastes generates a potential fertilizer, the digested substrate (digestate). The aim of this work was to study the feasibility of using the composted solid fraction of a digestate obtained after the codigestion of cattle manure and maize-oat silage as a component in the formulation of growing media for the commercial seedling production of three species: tomato (Lycopersicon esculentum Mill.), muskmelon (Cucumis melo L.), and pepper (Capsicum annuum L.). Four substrates were compared: pure peat (control) and three mixtures containing 25%, 50%, and 75% by volume of compost with the corresponding amount of peat. Physical, physicochemical, and chemical analyses of the different growing media were carried out and the effects of the different mixtures of peat/compost on seed germination and on the nutritional status of the seedlings were also studied. In general, compost addition neither influenced negatively the physical and physicochemical properties nor produced any reduction in the germination rate in the species studied, but it did enhance the seedlings' nutritional status.

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Three N-Boc-protected amino acids substituted with a mesityl ( 2,4,6-trimethylphenyl) group were synthesized in enantiomerically pure form, either by asymmetric epoxidation or by aminohydroxylation as the source of chirality. The 3-mesityloxirane-2-methanol 7, easily available in high enantiomer purity by Sharpless epoxidation, was converted into 3-{[(tert-butoxy)carbonyl]amino}-3-mesitylpropane-1,2-diol 9 by a regio-and stereoselective ring opening with an ammonia equivalent (sodium azide or benzhydrylamine), followed by hydrogenation and in situ treatment with (Boc) 2 O (Boc [(tert-butoxy)carbonyl]) (Scheme 3). Oxidative cleavage of the diol fragment in 9 afforded N-[(tert-butoxy)carbonyl]-a-mesitylglycine 1 of > 99% ee. This amino acid was also prepared in enantiomerically pure form starting from 2,4,6-trimethylstyrene (11) by a regioselective Sharpless asymmetric aminohydroxylation, followed by a 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO)-catalyzed oxidation (Scheme 4). On the other hand, 1-[(tert-butoxy)carbonyl]-2-{{[(tert-butyl)dimethylsilyl]oxy}methyl}-3-mesitylaziridine 14 was prepared from 9 by a sequence involving selective protection of the primary alcohol (as a silyl ether), activation of the secondary alcohol as a mesylate, and base-induced (NaH) cyclization (Scheme 5). The reductive cleavage of the aziridine ring (H 2 , Pd/C), followed by alcohol deprotection (Bu 4 NF/THF) and oxidation (pyridinium dichromate (PDC)/DMF or (TEMPO)/NaClO) provided, in high yield and enantiomeric purity, N-[(tert-butoxy)carbonyl]-b-mesitylalanine 2. Alternatively, the regioselective ring opening of the aziridine ring of 14 with lithium dimethylcuprate, followed by silyl-ether cleavage and oxidation lead to N-[(tert-butoxy)carbonyl]-b-mesityl-b-methylalanine 3. A conformational study of the methyl esters of the N-Boc-protected amino acids 1 and 3 carried out by variable-temperature 1 H-NMR and semi-empirical (AM1) calculations shows the strong rotational restriction imposed by the mesityl group.