Lactones functionalized, synthesis

Lundt I (2003) Iminosugars, isoiminosugars, and carbasugars from activated carbohydrate lactones efficient synthesis of biologically important compounds. In Witzak ZJ, Tatsuta K (eds) Carbohydrate synthons in natural products chemistry synthesis, functionalization and applications. ACS Symposium Series, vol 841. American Chemical Society, Washington, DC,pp 117-140... 

TBR widely used for all sorts of hydrotreatments in petro and commodity chemicals, it is now adopted in finer chemicals. Intermediates hydrogenation includes quinones, sugars, lactones, functional aromatics, etc... Despite continuous operation, small size TBR can be adapted to batch-wise synthesis by multiple recycling of L product. Example trifluoracetic acid hydrogenation [28]. 

Whitesell s synthesis of ( )-sarracenin [( )-495] (Vol. 4, p. 501, Ref. 314) has been published in full." It is worthwhile noting certain difficulties reported at the end of the synthesis involving the apparently simple steps shown in Scheme 48. Partial reduction of the lactone function in 496 with diisobutylaluminum hydride requires two equivalents, the first of which is taken up by complexation with the carbomethoxy group. Even with this problem solved, the yield of sarracenin [( )-495] from 496 was only 15%, and it is impossible to see where the loss was because of the instability of the intermediate compounds.Because both epimers of 497 were available in an earlier step toward 496, Whitesell also synthesized the as yet unnatural episarracenin with an epimeric 8-methyl group. 

Fontaine and coworkers have recently reported the synthesis of a supported aza-lactone via atom radical transfer polymerization (ATRP) [9]. This method involved the preparation of a Wang resin-supported initiator, followed by subsequent ATR polymerization between 2-vinyl-4,4-dimethyl-5-oxazolone (VAZ) and styrene to generate several macroporous, aza-lactone functionalized resins with different architectures. These were shown to scavenge benzyl amines in a highly efficient fashion (Scheme 8.5). 

We will turn our attention toward the synthesis of macrocyclic lactones, macrocyclic lactams, cyclopeptides, and macrocarbocycles, which are abundant in nature. Retrosynthetic cleavage of the lactone function, lactam function, and cycloalkanes provides an co-hydroxy-acid, an oo-amino-acid, and an open-chain hydrocarbon deriv-... 

In 1961, two experiments which provided the basis for deducing the skeleton of enmein were carried out by Kanatomo (75, 16). In the first he obtained l-ethyl-4(3,3-dimethylcyclohexyl)-benzene (II) whose structure was proved by synthesis (75). In the second he isolated retene (III) by selenium dehydrogenation of the material obtained by LiAlH4 reduction of enmein (16). Thus enmein was proved to be a diterpene and a phyllocladene (IV) skeleton was proposed for it (16). Kubota and coworkers (77) deduced the presence of a hemiacetal ring (V) and partial structure (VI), with the lactone function part of a six-membered ring, on the basis of chemical evidence and spectral data of various derivatives, and advanced four formulas including (VII) as possible structures for enmein. 

Fleet s group have examined the utility of carbohydrate-derived 2-azido- and 2-iodo-lactones for synthesis of novel, highly functionalized cyclopentanes and cyclohexanes. The azido lactone 11 undergoes KF-catalysed intramolecular aldol reaction to give 12 (major) and 13 (minor). The minor isomer arises through epimerization at C5 prior to the aldol cyclization. Lactone hydrolysis of the major isomer leads to 15. Similar hydrolysis of the minor isomer yields 16, and thus epimerization via retro-aldol must precede lactone ring opening via the intermediacy of 14. 

The results obtained showed that carbon, oxygen, or nitrogen functionalities are readily introduced into the a,p positions of the lactone moiety. In this way, useful precursors for natural product synthesis are accessible (88TL5317). 

The fungal metabolite (+)-brefeldin A (325) displays potent antitumor, antifungal, antiviral, antimitotic, and immunosuppressive activities. Recently, Romo and Wang described a highly concise total synthesis of 325 by a combined /J-lactone-CM approach (Scheme 63), that again underlines the high tolerance of sensitive functionality exhibited by the second-generation Ru catalysts [ 145]. 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

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