Synthesis of a novel N-1 carbocyclic, N-9 butyl analogue of cyclic ADP ribose (cADPR) Aldo Galeone, Luciano Mayol, p Giorgia Oliviero, Gennaro Piccialli and Michela Varra Dipartimento di Chimica delle Sostanze Naturali, Universita Á di Napoli `Federico II',Via D. Montesano 49, I-80131 Napoli, Italy Received 27 July 2001; accepted 22 November 2001 Abstract ÐA new analogue 1 of cADPR was prepared through a synthetic pathway starting from 6-chloropurine 2 which underwent two sequentialalkylationsatN-9andN-1,withformationoftheintermediate 8. The successive bis-phosphorylation of hydroxyalkyl functions, followed by deprotection and reprotection steps, afforded the derivative 13, the substrate for the cyclization reaction. This was carried out accordingtotheMatsudaprocedureandledtotheintramolecularpyrophosphatebondformation,thusaffording 14.The®naldeprotectionof 14, in alkaline conditions, gave the target compound 1 in good yield. q 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction Cyclic-ADP ribose (cADPR, Fig. 1), a naturally occurring compoundrelatedtoNAD 1 ,isaCa 21 messenger,important in regulating various cellular functions in a wide range of species including humans. 1 This metabolite is capable of mobilizing calcium ions more actively than inositol 1,4,5- triphosphate (IP 3 ), 2 through a completely independent mechanismofactionfromIP 3 . 3,4 Severalenzymesinvolved in the metabolism of cADPR have been described, among which the ubiquitous ADP-ribosyl cyclase, ®rst discovered in sea urchin eggs and particularly abundant in Aplysia california. The Aplysia cyclase, whose sequence is homo- logoustoantigensCD38onhumanlymphocytesandBST1/ BP3 on bone marrow cells, shares with all members of the cyclasefamilyasigni®cantcatalyticactivityinthecycliza- tionofNAD 1 and NADP 1 tocADPR. 5±9 This property has been exploited to enzymatically produce more stable cADPR analogues as tools to investigate the biological role of cADPR. In fact, such studies are severely prevented bythehighlabilityofthiscalcium-releasingmetabolite(the N-1 ribosyl bond is rapidly hydrolyzed in neutral aqueous solution, even in the absence of enzymes) coupled to its extremely low concentration in cells. On the other hand, theanalogues,whichcanbeobtainedbyenzymaticcycliza- tion of modi®ed substrates are limited due to the enzyme speci®city. Thus, chemical methods are needed to prepare new and more stable cADPR analogues. Several laboratories, in order to obtain molecules having more stable linkages, have prepared N-1or N-9 carbocyclic analoguesofcADPR.Tothisend,Matsudaandco-workers havereportedthe®rsttotalsynthesisofastableanalogueof cADPRhavingacarbocyclicribosemimicunitlinkedatthe N-1positionoftheinosinebase 10 (cIDPR).Itiswellestab- lished that structural modi®cations of naturally occurring nucleosides may produce new derivatives capable of exert- ing interesting and useful biological properties. 11,12 This Tetrahedron 58 (2002) 363±368 Pergamon TETRAHEDRON 0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII:S0040-4020(01)01162-0 Figure 1. Keywords: cADPR; pyrophosphate bond; cyclization. p Corresponding author. Tel.: 139-81-678-508; fax: 139-81-678-552; e-mail: mayoll@unina.it