Synthesis and characterization of all four diastereomers of 3,4-dichloro-2-pentanol, motifs relevant to the chlorosulfolipids

The Rise of Trichlorides Enabling an Improved Chlorine Technology

Chlorine plays a central role for the industrial production of numerous materials with global relevance. More recently, polychlorides have been evolved from an area of academic interest to a research topic with enormous industrial potential. In this minireview, the value of trichlorides for chlorine storage and chlorination reactions are outlined. Particularly, the inexpensive ionic liquid [NEt₃ Me][Cl₃ ] shows a similar and sometimes even advantageous reactivity compared to chlorine gas, while offering a superior safety profile. Used as a chlorine storage, [NEt₃ Me][Cl₃ ] could help to overcome the current limitations of storing and transporting chlorine in larger quantities. Thus, trichlorides could become a key technique for the flexibilization of the chlorine production enabling an exploitation of renewable, yet fluctuating, electrical energy. As the loaded storage, [NEt₃ Me][Cl₃ ], is a proven chlorination reagent, it could directly be employed for downstream processes, paving the path to a more practical and safer chlorine industry.

Kinetic Resolution of Racemic Aldehydes through Asymmetric Allenoate γ-Addition: Synthesis of (+)-Xylogiblactone A

A synthesis of (+)-xylogiblactone A has been achieved from t-butyl 2-methylbuta-2,3-dienoate in a linear three-step sequence. The key elements of the synthesis include a kinetic resolution of racemic 2-silyoxyaldehyde through the allenoate γ-addition to yield the γ-adduct as a single isomer and the subsequent gold catalysis to form the butenolide core. For a general method, the kinetic resolution of several racemic 2-silyloxyaldehydes is also performed to provide products in high levels of stereoselectivity with unusual anti-Felkin-Anh addition fashion.

Synthesis of malhamensilipin A exploiting iterative epoxidation/chlorination: experimental and computational analysis of epoxide-derived chloronium ions

We report a 12-step catalytic enantioselective formal synthesis of malhamensilipin A (3) based upon an iterative epoxidation/chlorination strategy.

We report a 12-step catalytic enantioselective formal synthesis of malhamensilipin A (3) and diastereoisomeric analogues from (E)-2-undecenal. The convergent synthesis relied upon iterative epoxidation and phosphorus(v)-mediated deoxydichlorination reactions as well a titanium-mediated epoxide-opening to construct the C11–C16 stereohexad. The latter transformation occurred with very high levels of stereoretention regardless of the C13 configuration of the parent epoxide, implicating anchimeric assistance of either the γ- or δ-chlorine atoms, and the formation of chloretanium or chlorolanium ions, respectively. A computational analysis of the chloronium ion intermediates provided support for the involvement of chlorolanium ions, whereas the potential chloretanium ions were found to be less likely intermediates on the basis of their greater carbocationic character.

Asymmetric total synthesis of danicalipin A and evaluation of biological activity

Asymmetric total synthesis of danicalipin A was achieved. The synthesis was characterized by diastereoselective introduction of chlorine atoms. Biological activities with synthetic danicalipin A, its enantiomer, and racemate were also evaluated toward brine shrimp. Both enantiomers of danicalipin A showed almost the same activity.

Asymmetric total synthesis of (+)-danicalipin A

A convergent asymmetric total synthesis of (+)-danicalipin A is accomplished, in which two chlorinated fragments are stereoselectively joined by 1,3-dipolar coupling, leading to the confirmation of the absolute configuration of the natural product.

Catalysis of phosphorus(V)-mediated transformations: dichlorination reactions of epoxides under Appel conditions

A stereospecific triphenylphosphine oxide-catalyzed 1,2-dichlorination reaction of epoxides has been developed. The reaction is effective for a range of terminal and internal epoxides. In contrast to the classical Appel-type dichlorination of epoxides, oxalyl chloride is used as a stoichiometric reagent to generate the chlorophosphonium salt responsible for dichlorination from catalytic triphenylphosphine oxide.

A concise enantioselective synthesis of the chlorosulfolipid malhamensilipin A

The first enantioselective synthesis of a member of the chlorosulfolipid family of natural products is reported. All of the polar substituents of malhamensilipin A are introduced with high stereoselectivity, and the unique (E)-chlorovinyl sulfate is created by a chemo-, regio-, and stereoselective E2 elimination of HCl in a reaction that likely has a counterpart in the biosynthesis of this fascinating natural product.

Structure revision and absolute configuration of malhamensilipin A from the freshwater chrysophyte Poterioochromonas malhamensis

Malhamensilipin A (2), a bioactive chlorosulfolipid initially reported in 1994 from the freshwater alga Poterioochromonas malhamensis, was reinvestigated for its structural and stereochemical features. HRESIMS data revealed that 2 possesses two sulfate groups rather than the one originally reported. A combination of J-based configurational and Mosher's analyses led us to assign its absolute configuration as 11R, 12S, 13S, 14R, 15S, and 16S. Finally, comparison of (1)H and (13)C NMR chemical shifts with synthetic standards confirmed that malhamensilipin A (2) possesses a terminal double bond of E configuration.

Conformational and configurational analysis in the study and synthesis of chlorinated natural products

The first detailed study of the J-based configuration analysis method in chlorinated hydrocarbons and chlorohydrins is presented along with the development of a spectroscopic database that facilitates configurational assignment of these structures. The data are generated through the investigation of model structures in solution by NMR spectroscopic methods and in the solid state by X-ray crystallography. Consequently, complete conformational analysis of trichlorinated hexane-1,2- and -1,3-diols is presented. The investigations in chlorinated systems for the first time attest to the relevance, reliability, and accuracy of the spectroscopic approach in configurational assignment, which had been otherwise developed for polyketides. During the synthesis of the various molecules that constitute the database and exemplify the various possible stereochemical patterns, a number of observations were made that underscore the unique features of these chlorinated systems. Thus, certain diastereomeric subclasses of 4,5-dichloro-2,3-epoxyhexane-1-ols display a propensity to undergo ring-opening reactions at C-3 with concomitant inversion of configuration at the neighboring C-Cl at C4, implicating the intermediacy of chloronium ions. The observations of positional and stereochemical scrambling in polychlorinated hydrocarbons underscore the necessity of a spectroscopic database that enables rapid, reliable configurational assignment of chlorinated natural products and intermediates en route to these.

Relative stereochemistry determination and synthesis of the major chlorosulfolipid from Ochromonas danica

The relative stereochemistry of the major chlorosulfolipid of the chrysophyte alga Ochromonas danica, to which we have given the name "danicalipin A", is reported. The first synthesis of this lipid, via several stereospecific electrophilic additions to alkenes, serves to corroborate the stereochemical assignment made by NMR spectroscopy. The synthesis strategy described should be applicable to other chlorosulfolipids and should provide access to sufficient material for studies of the lipid's properties and function in membranes.