Dioxolanone, ring opening

Dutton reported on the synthesis of an e-caprolactam analog of an anthelmintic cyclic peptide. The a-hydroxy-e-caprolactam 44 was generated in an ex chiral pool synthesis staring from malic acid. The a-hydroxy carboxylic acid unit was protected as a dioxolanone in 43. The protective group served simultaneously as the reactive function during cyclization lactam 44 formation succeeded by ring opening of the dioxolanone 43 by the nucleophilic attack of the amino function, Eq. (8) [14]. 

Narasaka et al. demonstrated the utility of titanium-ligand complexes in the resolution of chiral a-aryl esters [52]. Ti(Oi-Pr)4-ligand 56 complex resolves 2-pyridine thioesters with high selectivities (fcrei=26-42, see Scheme 13). Seebach and co-workers have examined titanium-TADDOLate complexes as reagents for the ring opening of meso anhydrides, dioxolanones, and azalactones [53]. Addition of an achiral isopropoxide source renders the desymmetrization of meso... 

R)- and (S)-f-Butyl-5-methylene-l,3-dioxolan-4-one, a Chiral a-Alkoxy Acrylate. It is also possible to introduce an ex-ocyclic double bond onto the dioxolanone ring, as in compounds (9)-(ll), derived from lactic and malic - acids. These a,3-unsaturated carbonyl derivatives are acceptors for radical additions and undergo cycloadditions with dienes and heterodienes. The Diels-Alder adduct (12) of ent-(9) with cyclopentadiene is formed with exo selectivity (96 4) and serves as aprecursor to norbomenone (13). Cycloadduct (14), obtained from methylenedioxolanone (9) and an open-chain triene, is also the result of an exo addition and is used in tetronolide synthesis. ... 

B. Second Approach to the Doubly Branched Ether Linkage Ring Opening of a 1,3-Dioxolanone... 

B. SECOND APPROACH TO THE DOUBLY BRANCHED ETHER LINKAGE RING OPENING OF A 1,3-DIOXOLANONE... 

Although the opening of 17 with bis(trimethylsilylacetylene) was successful, it is noteworthy to mention two other approaches that employed related to ring openings of 1,3-dioxolanones (Scheme 12). On the basis of studies with acetal templates, we expected that an ethyl group could be transferred to the C(2) center with retention of configuration after C(2)-0(3) bond scission upon treatment of 1,3-dioxolanone 32 with triethylaluminium. In addition, 14 might be constructed from 1,3-dioxolanone 33 by treatment with DIBAL-H. However, these approaches... 

Opening of the dioxolanone ring with dimsyl anion affords jS-ketosulfoxide 213, which is subsequently converted to acetyl derivative 214 by extrusion of sulfur with aluminum amalgam in 90% overall yield. The cyclic boronate 215, with the desired stereochemical configuration at both hydroxyl groups, is formed by treatment of 214 with phenylboronic acid. 

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