Latent Aldehyde Research Articles

Oxa bowls: synthesis and C-H...O mediated solid state structure of pentaoxa-[5]-peristylane.

We have conceptualized [n]-oxa-[n]-peristylanes as a new family of "oxa bowls" having a crownlike shape and potential C(nv)() symmetry. Recognizing their equivalence to the corresponding [n]-formyl-[n]-cycloalkanes, we have conceived of a general synthetic strategy in which "intramolecular cascade acetalizations" constitute the pivotal step. As our first synthetic effort, we describe the synthesis of pentaoxa-[5]-peristylane 3b from the readily available Diels-Alder adduct 10 of 5,5-dimethoxy-tetrachlorocyclopentadiene and maleic anhydride. The norbornyl framework of 10 serves as the rigid structural matrix to build the stereochemical features and latent aldehyde functionalities as in 9 through a series of functional group adjustments. Ozonation of 9 furnished 3b in a one-step transformation in which five tetrahydrofuran rings were generated. While 3b exhibited C(5v) symmetry in solution, its symmetry in the solid state was observed to be C(s) by X-ray crystallography. In the solid state, 3b is endowed with a multicolumnar architecture, whose distinctive features include C-H...O interactions involving the less acidic cyclopentane hydrogens. Indeed, all the 10 CH moieties and 5 oxygen atoms (through both the lone pairs) of 3b (C(10)H(10)O(5)) are involved in short C-H...O contacts (strong and soft) and its crystal structure indicates marked proclivity toward maximal hydrogen bonding.

The Synthesis of a Sulfone Containing Analogue of the Esperamicin-A1Aglycone: A Hetero Diels-Alder Approach

The hetero Diels-Alder reaction of methyl/ethyl thioglyoxylate, generated in situ from the corresponding anthracene adduct, with a series of dienes was studied as a route to a key 3,4-dihydro-2H-thiopyran derivative bearing an acetylene function at C-2, and hydroxyl groups at C-3 and C-4. Such a molecule is a planned intermediate in the synthesis of a sulfone containing analogue of esperamicin-A1. In this context, particular attention was directed to the hetero Diels-Alder reaction with polyfunctionalized dienes substituted at C-1 by a latent aldehyde function, and at C-4, C-2 and/or C-3 by ether substituents.

ChemInform Abstract: N‐Acyl‐5,5‐dimethyl‐oxazolidin‐2‐ones as Latent Aldehyde Equivalents.

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N-acyl-5,5-dimethyl-oxazolidin-2-ones as latent aldehyde equivalents

N-acyl-5,5-dimethyl-oxazolidin-2-ones can function as versatile latent aldehyde equivalents - reductive cleavage with DIBAL-H affords aldehydes in good yield, while tandem DIBAL-H/Wittig methodology affords α,β-unsaturated esters.

Total Synthesis of γ-Hydroxy-α,β-Unsaturated Aldehydic Esters of Cholesterol and 2-Lysophosphatidylcholine

Free radical-induced oxidation of polyunsaturated fatty esters in low-density lipoproteins (LDLs) generates 2-lysophosphatidylcholine (PC) and cholesterol esters of γ-hydroxy-α,β-unsaturated aldehydic acids that covalently modify LDL protein, and protein adducts of the corresponding acids are found in human blood. The chemistry and structures of these compounds resemble those of (E)-4-hydroxy-2-nonenal (HNE), previously considered the most cytotoxic aldehyde released during peroxidation of linoleate and arachidonate esters. The present report details total syntheses of 2-lyso-PC and cholesteryl esters of (E)-9-hydroxy-12-oxododec-10-enoic and (E)-5-hydroxy-8-oxooct-6-enoic acid that presumably are derived in vivo from linoleate and arachidonate esters, respectively. The syntheses depend on the use of a 3,3-dimethyl-2,4-dioxolanyl moiety as a latent aldehyde from which the chemically sensitive γ-hydroxy-α,β-unsaturated aldehyde array can be generated in the final step. For the cholesteryl esters, generation of the aldehyde group by oxidative cleavage of a vicinal diol could be accomplished in very good yields with periodate. However, for esters of 2-lyso-PC, the target aldehydes were not obtained upon treatment of vicinal diol precursors with periodate owing to a novel oxidative cleavage of the γ-hydroxy-α,β-unsaturated aldehydes by periodate. Fortunately, treatment of the vicinal diol precursors with Pb(OAc)4 at −80 °C delivered good yields (82−85%) of the desired phospholipid aldehydes.

Synthesis of Squamostanal-A.

The first synthesis of squamostanal-A (1), separated as a degradation product of tetrahydrofuranic acetogenins, is described. Iodide 7, which corresponds to the latent aldehyde moiety of 1, was prepared through a 2-step sequence from 13-[tetrahydropyran-2'- yloxy]-2-tridecyn-l-ol (5). The NaHMDS-based coupling reaction of 7 with γ-lactone 8 gave compound 9, which by a 3-step sequence, was coverted to 1.

Functionalized polymeric liposomes. Efficient immobilization of alpha chymotrypsin

A polymerizable phospholipid has been synthesized having a latent aldehyde moiety in the head group (1). Photopolymerized vesicles which have been prepared from this phosphatidylcholine have been successfully conjugated to alpha chymotrypsin. A high degree of loading was achieved with significant retention of enzymatic function.