Monolayer and differential scanning calorimetry studies have been performed on synthetic, stereochemically uniform glyceroglucolipids having saturated, ether-linked alkyl chains. The limiting area, A0 = 40 A2 X molecule-1, resulting from the monolayer measurements of the glucolipids is comparable to the A0 value found for phosphatidylethanolamine lipids. The area corresponds to twice the value observed with saturated straight chain fatty acids, which indicates that at high surface pressure the space requirement of the glucose head group does not exceed that of the two alkyl chains. The apparent specific heat capacities of the glucolipid dispersions have been found to be higher than those of corresponding phospholipids. They can be approximated from group parameters with the additional assumption that the experimental partial molar heat capacity of glucose is valid for the glucose head groups of the lipids. The transition enthalpies of the C16 and C18 glyceroglucolipids are clearly larger than the delta H values of corresponding phospholipids, while the C14 glyceroglucolipid has the same transition enthalpy as dimyristoylphosphatidylethanolamine or ditetradecylphosphatidylethanolamine. Glucolipids exhibit gel to liquid-crystalline phase transition temperatures which are only slightly lower than those of their phosphatidylethanolamine analogues, although they are uncharged molecules. Like phosphatidylethanolamine the glucolipids do not show a pretransition; however, with the C14 glucolipid a highly cooperative posttransition, approximately 5 deg above the main transition, has been found. Calorimetric experiments with a C14 glucolipid, in which the hydroxyl protons of the glucose moiety have been exchanged by deuterium, suggest that the posttransition might reflect structural changes of the head group.(ABSTRACT TRUNCATED AT 250 WORDS)
Starting with D-mannitol, the yield of the synthesis of 3-0-benzyl-sn-glycerol (1) could be improved. The regioselective alkylation of 1 at the primary hydroxy group to the 1-0-alkyl-3-0-benzyl-sn-glycerols 3 was achieved by using the dibutylstannylene protecting group. The 1-0-alkyl-2-0-methyl-snglycerols 4, readily obtainable from 3, were successfully glycosylated under the conditions of the Koenigs-Knorr reaction to give l-O-alkyl-2-O-methyl-3-O-~-~-glycosyl-sn-glycerols.
Die Synthese langkettiger 2-0-Benzyl-3-0-alkyl-sn-glycerine 5 konnte so verbessert werden, d d diese Verbindungen in ausreichenden Ausbeuten fur Glycosylierungsversuche zur Verfugung stehen. Die Glycosylierung dieser Verbindungen mit a-Acetobrommaltose nach einem modifizierten Koenigs-Knorr-Verfahren fiihrt nach Entfernung der Schutzgruppen in guten Ausbeuten zu den Titelverbindungen 9, die Vertreter der Alkylglycerylether-Lysoglycolipide sind. Einige Eigenschaften dieser amphiphilen Verbindungen mit einer nichtionischen Kohlenhydratkopfgruppe unterscheiden sich kaum (kritische Micellenkonzentration, hamolytische Aktivitat), andere sehr stark (Antitumorwirkung) von den Eigenschaften der analogen Verbindungen mit zwitterionischer Phosphorylcholinkopfgruppe.
Stereoselective Synthesis of Long-chain l-O-(~-~-Maltosyl)-3-O-alkyl-sn-glycerols
(Alkyl Glyceryl Ether Lysoglycolipids)The synthesis of long-chain 2-0-benzyl-3-0-alkyl-sn-glycerols 5 was improved, making these compounds easily accessible for glycosylation experiments. Glycosylation with a-acetobromomaltose following a modified Koenigs-Knorr procedure after removal of the protective groups yielded the title compounds 9 in good yields. These compounds represent examples of alkyl glyceryl ether lysoglycolipids. Some properties of these amphiphilic compounds with a nonionic carbohydrate head-group differ not much (critical micell concentration, hemolytic activity), other properties differ very much (antitumor efficiency) from the properties of the analogous compounds with a zwitterionic phosphorylcholine head-group.Glyceryletherlipide der Srukturtypen I -111 mit langkettigen, methylverzweigten oder unverzweigten, gesattigten Alkylgruppen ( b m . .Acylgruppen in II) sind als Bestandteile vieler Membransysteme und Sekrete sowie als physiologisch hochwirksame Verbindungen sehr vie1 weiter verbreitet 11, als noch vor einigen Jahren angenommen21.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.